The present study evaluated physical, chemical and morphological changes in lungs of mice infected with Paracoccidioides brasiliensis. The animals were inoculated with 0.1 mL of fungal suspension of the P. brasiliensis 18 isolate and were euthanized 1, 2, 4, and 8 weeks after inoculation. The upper left lobe of the lung was isolated, fixed and processed for paraffin embedding. The sections were stained with H&E for histopathological study, with Gomori-Grocott to locate and identify the fungus, and with TUNEL immunostaining to detect the occurrence of programmed cell death. The lower and middle right lobes were analyzed by Fourier Transform Infrared Photoacoustic Spectrocopy (FTIR-PAS) to investigate physical and chemical features of the infected lungs. The results showed that lungs infected by P. brasiliensis underwent structural changes that varied according to the time period analyzed, and that changes in the absorption bands of different chemical groups resulted from these morphological changes. The results suggest that the combination of FTIR-PAS spectroscopy with morphological evaluation is an effective procedure for the study of paracoccidioidomycosis, one of the most important systemic mycoses that can damage the lung architecture and consequently impair the respiratory function.

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Photoactive spherical metal and semiconductor nanoparticles (NPs) are smart systems that exhibit unique properties, such as a high surface-to-volume ratio, a broad-absorption spectrum, and size-dependent properties. They are capped with a considerable number of ligands required to give rise to stable organic and aqueous NP colloidal solutions. In addition, the ligands can also be used to introduce functionality at the NP periphery. In this case, the NP could act as a 3D-scaffold which would make a high local concentration of a functional moiety at the NP periphery possible, moreover the photophysical properties of the NP could be tuned. The combined action of the organic capping and the inorganic core can exert an encapsulating effect, i.e., the organic capping could establish specific interactions with nearby molecules and this would enable the molecules to approach or interact with the NP surface. Therefore, the nanoparticle core and the ligand can work together providing the overall hybrid system with new properties or capacities. The relevance of the cooperative action between the spherical photoactive core and the capping are shown in this report with several recent examples developed by my research group, some of them in collaboration with other groups.

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The photosensitization effect of three perylene dye derivatives on titanium oxide nanoparticles (TiO₂ NPs) have been investigated. The dyes used, 1,7-Dibromoperylene-3,4,9,10-tetracarboxy dianhydride (1), 1,7-Dipyrrolidinylperylene-3,4,9,10-tetracarboxy dianhydride (2), and 1,7-bis(4-tert-butylphenyloxy)perylene-3,4,9,10-tetracarboxy dianhydride (3), have in common bisanhydride groups that convert into TiO₂ binding groups upon hydrolysis. The different substituents on the bay position of the dyes enable tuning of their redox properties to yield significantly different driving forces for photoinduced electron transfer (P_eT). Recently developed TiO₂ NPs having a small average size and a narrow distribution (4±1 nm) are used in this work to prepare the dye-TiO₂ systems under study. Whereas successful sensitization was obtained with 1 and 2 as evidenced by steady state spectral shifts and transient absorption results, no evidence for the attachment of 3 to TiO₂ was observed. The comparison of the rates of P_eT (k_PeT) for 1- and 2-TiO₂ systems studied in this work with those obtained for previously-reported analogous systems, having TiO₂ NPs covered by a surfactant layer [Hernandez, (2012) J. Phys. Chem. B. 117, 4568-4581], indicates that k_PeT for the former systems is slower than that for the later. These results are interpreted in terms of the different energy of the conduction band edge in each system.

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Photoactive materials based on dye molecules incorporated into thin films or bulk solids are useful for applications as photosensitization, photocatalysis, solar cell sensitization and fluorescent labeling, among others. In most cases, high concentrations of dyes are desirable to maximize light absorption. Under these circumstances, the proximity of dye molecules leads to the formation of aggregates and statistical traps, which dissipate the excitation energy and lower the population of excited states. The search for enhancement of light collection avoiding energy wasting requires accounting the photophysical parameters quantitatively, including the determination of quantum yields, complicated by the presence of light scattering when particulate materials are considered. In the present work we summarize recent advances on the photophysics of dyes in light scattering materials, with particular focus on the effect of dye concentration. We show how experimental reflectance, fluorescence and laser induced optoacoustic spectroscopy data can be used together with theoretical models for the quantitative evaluation of inner filter effects, fluorescence and triplet formation quantum yields and energy transfer efficiencies.

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In this study we report the synthesis and photochemical behaviour of a new family of photoactive compounds in order to assess its potential as singlet oxygen probes. The candidate dyads are composed by a singlet oxygen trap plus a naphthoxazole moiety linked directly or through an unsaturated bond to the oxazole ring. In the native state, the inherent great fluorescence of the naphthoxazole moiety is quenched; but in the presence of singlet oxygen, generated by the addition and appropriate irradiation of an external photosensitizer, a photooxidation reaction occurs leading to the formation of a new chemical entity whose fluorescence is two orders of magnitude higher than that of the initial compound, at the optimal selected wavelength. The presented dyads outperform the commonly used indirect fluorescent singlet oxygen probes in terms of fluorescence enhancement maintaining the required specificity for singlet oxygen detection in solution.

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Solar ultraviolet (UV) radiation, particularly its UVB (290-230 nm) spectrum, is the primary environmental stimulus leading to skin carcinogenesis. Several botanical species with antioxidant properties have shown photochemopreventive effects against UVB damage. Costa Rica's tropical highland blackberry (Rubus adenotrichos) contains important levels of phenolic compounds, mainly ellagitannins and anthocyanins, with strong antioxidant properties. In this study, we examined the photochemopreventive effect of R. adenotrichos blackberry juice (BBJ) on UVB-mediated responses in human epidermal keratinocytes and in a three dimensional reconstituted normal human skin equivalent (SE). Pre-treatment (2 h) and post-treatment (24 h) of normal human epidermal keratinocytes (NHEKs) with BBJ reduced UVB (25 mJ/cm²)-mediated (i) cyclobutane pyrimidine dimers (CPDs) and (ii) 8-oxo-7,8-dihydro-2’-deoxyguanosine (8-oxodG) formation. Furthermore, treatment of NHEKs with BBJ increased UVB-mediated (i) poly(ADP-ribose) polymerase (PARP) cleavage and (ii) activation of caspases 3, 8 and 9. Thus, BBJ seems to alleviate UVB-induced effects by reducing DNA damage and increasing apoptosis of damaged cells. To establish the in vivo significance of these findings to human skin, immunohistochemistry studies were performed in a 3D SE model, where BBJ was also found to decrease CPDs formation. These data suggest that BBJ may be developed as an agent to ameliorate UV-induced skin damage.

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Pyrene fluorescence spectra have been recorded in 5 poly(alkyl methacrylate)s (where alkyl is ethyl butyl, isobutyl, cyclohexyl, and hexadecyl) over a 20-400 K temperature range. The changes in the position and the full width at half maximum (FWHM) of the 0-0 emission band (peak I) have been correlated with the structural characteristics of the alkyl groups in the different relaxation regimes of the polymers in order to assess the degree of coupling of the excited singlet states with the polymer cybotactic regions. Data treatment of the peak I positions using an electron-phonon model indicates that longitudinal optical modes are involved, and that the magnitude of the coupling depends on the polymer structure and follows the same trend as the glass transition temperatures. The same spectral parameters have been correlated also with ‘hole’ free volumes from positron annihilation spectroscopy over temperature ranges which span the glass or melting transitions of the polymers. Reasons why free volume and FWHM measurements follow the same trends, and other aspects of the systems, are discussed.

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Although the mechanisms of many chemiluminescence (CL) reactions have been intensively studied, no general model has been suggested to rationalize the efficiency of these transformations. In order to contribute to this task, we report here quantum yields for some well characterized CL reactions, concentrating on recent reports of efficient transformations. Initially, a short review on the most important general CL mechanisms is given, including unimolecular peroxide decomposition, electrogenerated CL, as well as the intermolecular and intramolecular catalyzed decomposition of peroxides. Thereafter, quantum yield values for several CL transformations are compiled, including the unimolecular decomposition of 1,2-dioxetanes and 1,2-dioxetanones, the catalyzed decomposition of appropriate peroxides and the induced decomposition of properly substituted 1,2-dioxetane derivatives. Finally, some representative examples of quantum yields for complex CL transformations, like luminol oxidation and the peroxyoxalate reaction, in different experimental conditions are given. This quantum yield compilation indicates that CL transformations involving electron transfer steps can occur with high efficiency in general only if the electron transfer is of intramolecular nature, being the intermolecular processes commonly inefficient. A notable exception of this general rule is the peroxyoxalate reaction which, also constituting an example of an intermolecular electron transfer system, possesses very high quantum yields.

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Fringing coral reefs provide a unique opportunity to study shallow aquatic ecosystems. A fringing coral reef system located in close proximity to a developed region was considered in this study. In such an environment the rate of decay of dissolved organic matter is high and the penetration of higher energy ultraviolet-B extends a greater influence on species diversity, particularly upon shallow benthic communities. Results from a nine month subsurface ultraviolet-B exposure measurement campaign performed at a site located on the southern Queensland coast (Hervey Bay, 25^oS) are presented in this research. For this, a novel dosimetric technique was utilised to measure long-term subsurface ultraviolet-B exposures. The resultant data set includes exposure measurements made during the significant La Niña event of late 2010 which resulted in unprecedented high sea surface temperatures and severe flooding across eastern Australia, impacting upon the lagoon regions of the Great Barrier Reef and Queensland's southern estuaries, including the study site. The influence of season, diurnal tidal variation, cloud cover and solar zenith angle were analysed over the campaign period. Mean minimum daylight water depth was found to be the most significant factor influencing subsurface ultraviolet-B.

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The spatial resolution of fluorescence microscopes is limited by diffraction to about half of the light wavelength, hampering the observation of many important intracellular processes. Recent emerging techniques have overcome that diffraction barrier using the temporal discrimination of close objects that are otherwise unresolved or blurred within the spatial resolution of the microscope. The key of these techniques is to switch the signal of fluorescence markers on and off exploiting their distinct molecular states, and detect and localize these markers at the single molecule level. This underlying principle highlights the critical role of the photophysical properties of the probes, and the importance of finding adequate switching mechanisms. Here, we present strategies to achieve fluorescence modulation based on novel molecular assemblies containing a [1,3]oxazine as the two-states, building-block responsible for the transformation. Two different triggering events, based on the photochromic and halochromic properties of the oxazine, induce a large absorption and emission bathochromic shift of a pendant fluorophore, as the ultimate fluorescence switching event. The implementation of these approaches to achieve spatial resolution beyond the diffraction limit is also discussed.

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Light availability is a main issue in autotrophic growth of photosynthetic microorganisms. The change of the suspended cells concentration and that of their chlorophylls content during microalgal growth alters the optical properties of the aqueous suspension.This brings about changes in the properties of the radiation field inside the reactor. In this work,we have computed the evolution in time of the local volumetric rate of absorption of photons inside a photobioreactor by means of a Monte Carlo simulation algorithm previously developed. From this study we have computed two operational variables that are useful tools for the analysis, performance comparison, optimization and scaling-up of photobioreactors: the average rate of photon absorption and the volumetric distribution function of photons absorption rates.Based on these two variables it is possible to sistematically quantify the degree of stratification of the culture medium, which is a decisive aspect that hampers the reactor efficiency regarding the energy usage for biomass production.

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Exposure to ultraviolet radiation (UVR) is a significant risk factor for age-related cataract, a disease of the human lens and the most prevalent cause of blindness in the world. Cataract pathology involves protein misfolding and aggregation of the primary proteins of the lens, the crystallins. Human γD-crystallin (HγD-Crys) is a major γ-crystallin in the nucleus of the human lens. We report here analysis of UVR-induced damage to HγD-Crys in vitro. Irradiation of solutions of recombinant HγD-Crys with UVA/UVB light produced a rise in solution turbidity due to polymerization of the monomeric crystallins into higher molecular weight aggregates. A significant fraction of this polymerized protein was covalently linked. Photo-aggregation of HγD-Crys required oxygen and its rate was protein concentration and UVR dose dependent. To investigate the potential roles of individual tryptophan residues in photo-aggregation, triple W:F mutants of HγD-Crys were irradiated. Surprisingly, despite reducing UVR absorbing capacity, multiple W:F HγD-Crys mutant proteins photo-aggregated more quickly and extensively than wild-type. The results reported here are consistent with previous studies that postulated that an energy transfer mechanism between the highly conserved pairs of tryptophan residues in HγD-Crys could be protective against UVR-induced photo-damage.

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Pterins, heterocyclic compounds widespread in biological systems, accumulate in the skin of patients suffering from vitiligo, a chronic depigmentation disorder. Pterins have been previously identified as good photosensitizers under UV-A irradiation. In this work, we have investigated the ability of pterin (Ptr), the parent compound of oxidized pterins, to photosensitize the oxidation of tyrosine (Tyr) in aqueous solutions. Tyr is an important target in the study of the photodynamic effects of UV-A radiation because it is oxidized by singlet oxygen (¹O₂) and plays a key role in polymerization and crosslinking of proteins. Steady UV-A irradiation of solutions containing Ptr and Tyr led to the consumption of Tyr and dissolved O₂, whereas the Ptr concentration remained unchanged. Concomitantly, hydrogen peroxide (H₂O₂) was produced. By combining different analytical techniques, we could establish that the mechanism of the photosensitized process involves an electron transfer from Tyr to the triplet excited state of Ptr. Mass spectrometry, chromatography and fluorescence were used to analyze the photoproducts. In particular, oxygenated and dimeric compounds were identified.

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In order to measure the fluence distribution in the upper room of a facility equipped with germicidal UV lamps a method has been developed utilizing iodide/iodate chemical actinometry together with spherical (1 cm) quartz irradiation chambers. The use of spherical vessels allows radiation from essentially all directions to be measured. Such a measurement allows an estimate of the radiation flux at a given point in space, i.e. the fluence rate. When a battery of spheres located at various points in a room are simultaneously irradiated, a measure of the fluence distribution can be obtained. The use of the iodide/iodate chemical actinometer is uniquely qualified to measure germicidal UV radiation. The purpose of this report is to provide details on how this system can be used to measure fluence rates. In particular, it describes how a hand-held colorimeter can be used to measure the absorbance changes in irradiated spheres.

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Electron transfer (ET) rate constants were determined by means of lifetime measurements for the fluorescence quenching and by laser flash photolysis for the triplet quenching of the dye eosin Y by p-benzoquinones in acetonitrile. The results represent a new aspect of the dependence of the rate constants with the driving force in the diffusion limit region. That is, the rate constants for singlet quenching in the highly negative region of ΔG_et do not decrease as predicted by Marcus theory, but rather show a small positive dependence on the driving force. However, it is found that, in the same free energy range, the triplet rate constants are lower than those for the singlet process. They also increase with the exergonicity of the reaction, but the dependence with ΔG_et is less marked than that found for the singlet reaction. Even at a Gibbs energy change of -1.0 eV the triplet quenching rate constants do not reach the theoretical diffusion limit. The results are analyzed using the current theories for diffusion-mediated ET reactions.

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Luminous click beetle is distributed almost exclusively in Central and South America with a single genus in Melanesia. Among these click beetles, the description of Melanesian species has been fragmentary, and its luciferase gene and phylogenetic relation to other click beetles still remain uncertain. We collected a living luminous click beetle, Photophorus jansonii in Fiji. It emits green-yellow light from two spots on the pronotum and has no ventral luminous organ. Here, we cloned a luciferase gene from this insect by RT-PCR. The deduced amino acid sequence showed high identity of ~85% to the luciferases derived from other click beetle species. The luciferase of the Fijian click beetle was produced as a recombinant protein to characterize its biochemical properties. The K_m for d-luciferin and ATP were 173 and 270 μm, respectively. The luciferase was pH-insensitive and the spectrum measured at pH 8.0 showed a peak at 559 nm, which was in the range of green-yellow light as seen in the luminous spot of the living Fijian click beetle. The Fijian click beetle luciferase was assigned to the Elateridae clade by a phylogenetic analysis, but it made a clearly different branch from Pyrophorus group examined in this study.

The thorax part of a luminous Fijian click beetle, Photophorus jansonii. The Fijian click beetle emits green-yellow light from the two spots on the pronotum. The recombinant luciferase was pH-insensitive and the spectrum measured at pH 8.0 showed a peak at 559 nm. This is the first report describing the luciferase from Melanesian luminous click beetle.

The very aspect (phototoxicity) that makes short-wavelength ultraviolet (UV) radiation an effective germicidal agent also is responsible for the unwanted side effects of erythema (reddening of the skin) and photokeratitis (“welder's flash” or “snow-blindness”). Overexposure to this short-wavelength UV radiation can produce these unwanted side effects from a very mild irritation of the skin and eyes to a rather painful case of photokeratitis. These effects are fortunately transient, as only superficial cells of the eye—the corneal epithelium—and the most superficial layer of the skin—the superficial epidermis—are significantly affected. Normal turnover of these cells soon erase the signs and symptoms of these effects. Radiant energy in the UV-C band has very shallow penetration depths which account for the very superficial nature of any injury to the skin and eyes from excessive exposure, minimum risk of delayed effects and at the same time the strong absorption by bioaerosols. Guidelines for human exposure to UV-C must be applied intelligently so as not to limit germicidal efficacy in upper-room ultraviolet germicidal irradiation.

The phototoxicity of UV-C radiation that is responsible for germicidal efficacy also is responsible for the annoying side effects, erythema and photokeratitis. Fortunately, these effects are acute, if they occur. The human exposure limits (ELs) (ACGIH) at the principal germicidal wavelength, 254 nm are based upon the most sensitive structure—the cornea. Large safety factors exist for erythema—and most importantly, for nonmelanoma skin cancer (NMSC). Guidelines for human exposure to UV-C must be applied intelligently in risk assessments so as not to limit germicidal efficacy in upper-room ultraviolet germicidal irradiation.

The photochemical and thermal reactivity of a number of acyl azide-substituted pyridine compounds, namely nicotinyl azide, isonicotinyl azide, picolinyl azide and dinicotinyl azide with investigated as saturated monolayers on a single-crystal Pt(111) surface in an ultrahigh vacuum chamber. Multilayers of the substrates exhibited a maximum rate of desorption at 270 K, above which, stable saturated monolayers formed as characterized by reflection-absorption infrared spectroscopy by observation of C=O and N₃ bands at 1700 cm⁻¹, and 2100 and 1300 cm⁻¹ respectively. The monolayers were stable up to 400 K. Photolysis of the monolayer (or heating above 400 K) results in the formation of the respective isocyanate intermediate after loss of nitrogen as evidenced by the appearance of a new infrared band at 2260 cm⁻¹ with concomitant loss of the azide bands. The resulting isocyanate saturated monolayer is stable in absence of nucleophiles, but can be quenched with appropriate nucleophiles.

Saturated monolayers of a number of acyl azide-substituted pyridine compounds, namely nicotinyl azide, isonicotinyl azide, picolinyl azide and dinicotinyl azide, were formed on single-crystal Pt(111) surfaces in a UHV chamber. These monolayers were characterized by RAIR and thermal programmed desorption. Photolysis or thermolysis of these saturated monolayers leads to the corresponding isocyanate via a Curtius rearrangement.

Photoreduction of 7H-benzo[e]perimidin-7-one (3-AOIA, A1) and its 2-methyl derivative (2-Me-3-AOIA, A2) by non-H-donating amines (1,4-diazabicyclo[2.2.2]octane [DABCO]; 2,2,6,6-tetramethylpiperidine [TMP]), and a hydrogen-donating amine (triethylamine [TEA]), has been studied in deaerated neat acetonitrile solutions using laser flash photolysis (LFP) and steady-state photolysis. The triplet excited states of A1 and A2 were characterized by a strong absorption band with λ_max = 440 nm and lifetimes of 20 and 27 μs respectively. In the presence of tertiary amines, both triplet excited states were quenched with rate constants close to the diffusional limit (k_q ranged between 10⁹ and 10¹⁰ M⁻¹ s⁻¹). The transient absorption spectra observed after quenching with DABCO and TMP were characterized by maxima located at 460 nm and broad shoulders in the range of 500–600 nm. These transient species are attributed to solvent-separated radical ion pairs and/or to isolated radical anions. In the presence of TEA, these transients undergo proton transfer, leading to the neutral hydrogenated radicals, protonated over the N1- and O-atoms. Transient absorption spectra of these transients were characterized by maxima located at 400 and 520 nm and 430 nm respectively. Additional support for these spectral assignments was provided by pulse radiolysis (PR) experiments in acetonitrile and 2-propanol solutions.

Photoreduction of 7H-benzo[e]perimidin-7-ones by amines proceeds through a stepwise electron-proton-electron transfer mechanism, which was studied by using laser flash photolysis, steady-state photolysis and pulse radiolysis. Later, to achieve the triplet state, the sequence of reaction generates a radical ion pair, which by proton transfer over the N1- and O-atoms of substrates yields two different hydrogenated radicals, likely in equilibrium. These neutral radicals by the second electron transfer lead to the metastable products. Transient absorptions for intermediaries were characterized by laser flash photolysis and pulse radiolysis.

To examine the effect of laser thermal injury on Langerhans cells (LC) within the epidermis, the dorsal skin of mice and hairless guinea pigs was exposed to varying levels of laser irradiation using a thulium laser at a wavelength of 2.0 μm. At 6, 24 and 48 h post irradiation, animals were euthanized, skin samples prepared for histology and the epidermis obtained and stained by major histocompatibility complex-II staining (mice) or ATPase assay (hairless guinea pigs) for the enumeration of LC. Mouse skin exhibited histological evidence of thermal damage at 24 h post irradiation at even the lowest dose (0.14 W) and decreases in the numbers of epidermal LC were observed at all doses and decreases were proportional to dose. In contrast, hairless guinea pig skin only showed consistent histological evidence of thermal damage at the highest dose of irradiation (0.70 W) at 24 and 48 h post irradiation and exhibited a statistically significant decrease in numbers of epidermal LC only at this dose. Thus, epidermal LC depletion occurred in the skin of both mice and hairless guinea pigs in response to laser treatment and the magnitude of depletion directly correlated with the extent of thermal damage both within and between species.

Mice and hairless guinea pigs were exposed to a thulium laser at a wavelength of 2.0 μm. Mouse skin exhibited histological evidence of thermal damage and decreases in epidermal Langerhans cells at 24 and 48 h following doses from 0.14 to 0.56 W. In contrast, hairless guinea pig skin only showed consistent histological evidence of thermal damage and the disappearance of Langerhans cells following the highest dose administered (0.70 W). These results suggest a correlation between thermal damage and Langerhans cell disappearance for both mice and hairless guinea pigs.

This study has been carried out to synthesize nano ZnO on wool fabric and also to investigate influences of nano photo reactors on wool fabric characteristics. Zinc acetate has been used as a precursor and the synthesis process has been done in water and water/ethanol media. The treated wool fabrics were heated at 80°C for 10 h to dehydrate Zn(OH)₂ obtaining ZnO. The fabric samples were then subjected to daylight for 7 days to examine the influence of nano ZnO photo reactor on the fabric properties. SEM images revealed the embedding of ZnO nanoparticles on the fabrics and X-ray diffraction verified the nanoparticles composition. The Yellowness Index (YI) of the fabrics was measured with Color Eye XTH that has been reduced with increasing pH, Zn(CH₃COO)₂ concentration, ethanol and heating. The lower water contact angle and time of water absorption confirmed higher hydrophilic properties of the treated fabrics. Interestingly, a higher tensile strength obtained on the wool fabrics proved the interaction of ZnO with protein chains of wool, which was verified through lower alkali solubility of treated fabric with nano ZnO and confirmed more benefits of the in situ synthesis process.

The main purpose of this work was to synthesize ZnO nano particles within the wool fabric. To do this, the pretreated wool fabric with protease was immersed in the solution of Zn(CH₃COO)₂, NH₃ and Na(OH) as precursor and distilled water or water/ethanol mixture as the reaction environment. The samples were then subjected to daylight for 7 days. The reactive oxygen species produced as a result of photocatalytic activities of nano ZnO, which have potential of decomposing impurities of wool fibers including the natural pigments and waxes. This leads to the hydrophilic and roughly white wool fabric surface.

2-Hydroxyethyl methacrylate (HEMA) was photopolymerized in the presence of Safranine (SfH⁺) and tetraphenyldiboroxane (TPhB). Polymerization results are correlated with the photochemistry of TPhB and its ability to aggregate forming hydrophobic domains (critical aggregation concentration, cac, 1.2 × 10⁻⁴ M). Polymerization was not observed when the TPhB concentration was below the cac, indicating that the polymerization is initiated in the hydrophobic environment. The quenching of the triplet state of SfH⁺ by TPhB and the generation of the semireduced species of SfH⁺ suggests an electron transfer from the boron compound to the excited dye, and that the resulting boron-centered radical initiates the polymerization process.

Tetraphenyldiboroxane (TPhB) can be used as visible-light photopolymerization coinitiator with the dye Safranine (SfH⁺). The mechanism involves the formation of a radical cation of the boron compound. Photophysical properties of the excited states of TPhB were also determined.

We present a novel method to calculate vitamin D₃–weighted exposure by integrating the incident solar spectral radiance over all relevant parts of the human body. Earlier investigations are based on the irradiance on surfaces, whereas our calculated exposure of a voxel model of a human takes into account the complex geometry of the radiation field. Assuming that sufficient vitamin D₃ (1000 international units) can be produced within the human body in one minute for a completely uncovered body in vertical posture in summer at midlatitudes (e.g. Rome, June 21, noon, UV index of 10), we calculate the exposure times needed in other situations or seasons to gain enough vitamin D₃. Our calculations show that the UV index is not a good indicator for the exposure which depends on the orientation of the body (e.g. vertical (standing) or horizontal (lying down) posture). Without clothing the exposure is dominated by diffuse sky radiation and it is nearly irrelevant how the body in vertical posture is oriented toward the sun. At the winter solstice (December 21, noon, cloudy) at least in central Europe sufficient vitamin D₃ cannot be obtained with realistic clothing, even if the exposure were extended to all daylight hours.

We present a novel method to calculate vitamin D3 weighted exposure by integrating the incident solar spectral radiance over all relevant parts of the human body. Earlier investigations are based on the irradiance on surfaces, whereas our calculated exposure of a human model takes into account the complex geometry of the radiation field. We calculate the exposure times needed to gain enough vitamin D3 for different situations and seasons. For December 21st (noon, cloudy) at least in central Europe sufficient vitamin D3 cannot be obtained with realistic clothing, even if the exposure were extended to all daylight hours.

BiVO₄-Silica composites were prepared and grafted with sulfonated cobalt phthalocyanine. The structural and chemical properties including crystalline phase, specific surface area, UV–Visible diffuse reflectance behavior, morphology and photocatalytic activity were investigated. Depending on the silica content and subsequently amounts of loaded phthalocyanine, various catalytic activities were observed. The sample containing nominal 15% silica and grafted with phthalocyanine showed less aggregated form of this organic dye, smaller and nanometric particles, and higher photocatalytic activity in degradation of 2,4,6-trichlorophenol.

A facile process was developed to produce BiVO₄-Silica composites with different silica contents. The composites were modified with sulfonated cobalt phthalocyanine. Both phthalocyanine and BiVO₄ are visible-light driven photoactive catalysts. It was observed that presence of silica led to anchorage of phthalocyanine due to surface modification. The sample with nominal 15% silica content showed the best photocatalytic activity in degradation of 2,4,6-trichlorophenol.

We have investigated the DNA binding interactions and in vitro photoactivated DNA damage induced by a neutral water soluble porphyrin derivative 5,10,15,20-tetrakis(2,4,6-trihydroxyphenyl)porphyrin (TTHPP) and its zinc derivative 5,10,15,20-tetrakis(2,4,6-trihydroxyphenyl)porphyrinato zinc(II) (Zn-TTHPP) upon visible light irradiation through various spectroscopic techniques and employing repair endonucleases. These porphyrin derivatives exhibited high affinity toward DNA through groove binding interactions as evidenced through the UV–vis absorption, emission, circular dichroism spectral and viscosity changes. Interestingly, the free base porphyrin derivative, TTHPP generated efficient singlet oxygen mediated DNA damage sensitive to formamidopyrimidine-DNA glycosylase (Fpg protein), when compared with its metal derivative and to the well-known photosensitizer, hematoporphyrin. These results provide direct evidence for the role of DNA binding mode as well as extent of interactions with DNA in the efficiency of photoactivated DNA damage induced by the neutral porphyrins, which are believed to be the ideal candidates for photodynamic therapeutic applications.

We describe interactions of neutral and water soluble porphyrins with DNA and their efficiency of photoinduced DNA damage. Uniquely these systems exhibited high affinity for DNA and efficient singlet oxygen mediated DNA damage sensitive to formamidopyrimidine-DNA glycosylase (Fpg protein), when compared with the well-known photosensitizer, hematoporphyrin. These results demonstrate the direct evidence for the role of the DNA binding mode and extent of interactions with DNA in the efficiency of the photoactivated DNA damage caused by the neutral porphyrins, which are believed to be the ideal candidates for photodynamic therapeutic applications.

Within this study, the erythemal ultraviolet (UV) exposure received by different parts of the body during four different activities is determined. Optoelectronic devices were used to measure the erythemal UV exposure at 10 different positions of the body. The measuring devices were fixed on the forehead, on the shoulders, on the arms, on the chest, on the thighs and on the lower legs. The measurements were performed during the following activities of the test persons: walking, sitting, lying and sitting up. The measurements were performed on four clear sky days in the early afternoon at 1 s interval. One measurement sequence was taking 30–40 min. For the analysis of the measured UV exposures, the ambient UV is taken as a reference to remove the atmospheric fluctuations on the measured UV exposure. The strong dependence of the UV exposure on the activity and on the orientation of the test person is shown. Most of the body parts receive the highest exposure, when the test subject is sitting up or lying. The shoulders are most at risk when the test person is walking, whereas during the activities sitting up and lying the legs are most at risk.

In this study, the erythemal ultraviolet exposure received by different parts of the body during four different activities is determined. The measurements were performed during the following activities: walking, sitting, lying and sitting up. The strong dependence of the UV exposure on the activity and on the orientation of the test person is shown. Most of the body parts receive the highest exposure, when the test subject is sitting up or lying. The shoulders are most at risk when the test person is walking, whereas during the activities sitting up and lying the legs are most at risk.

Numerous in vitro investigations have suggested that macroalgae exhibit regular geographic and depth distribution patterns in accordance with the light and temperature predominance at their habitats; however, there have been only a few similar studies concerning microalgae. We examined the potential influence of irradiance on patterns of distribution of four Cosmarium strains isolated from various climatic zones and cultured long term (>15 years) under a constant temperature–light regime. All the Cosmarium strains demonstrated physiological responses that were consistent with the light intensity prevailing at their source location, confirming that these responses are genetically preserved, as concluded from chlorophyll fluorescence and oxygen evolution rates measurements. Addition of inhibitors of chloroplast-encoded protein synthesis (chloramphenicol and streptomycin) and violaxanthin de-epoxidase (dithiothreitol) indicated that the Cosmarium strains developed “sun- or shade-plant” protection strategies, in accordance with the climate at their sampling sites. The polar Cosmarium strains exhibited a “shade-plant strategy”—to suffer some photoinhibition, but acquire increasing protection from photoinhibited PSII centers, whereas the tropical strains displayed a “sun-plant strategy”—to counteract photoinhibition of PSII by a high rate of repair of photoinhibited PSII reaction centers and a high xanthophyll cycle turnover.

Addition of inhibitors of chloroplast-encoded protein synthesis (chloramphenicol, CAP and streptomycin, SM) indicated that the Cosmarium strains developed “sun- or shade-plant” protection strategies, in accordance with the climate at their sampling sites. The polar Cosmarium strains (such as C. crenatum) exhibited a “shade-plant strategy”—to acquire increasing protection from photoinhibited PSII centers (i.e. they have distinctly low rates of D1-protein turnover), whereas the tropical strains (such as C. beatum) displayed a “sun-plant strategy”—to counteract photoinhibition of PSII by a high rate of repair of photoinhibited PSII reaction centers.

This article is a highlight of the study by Stamenkovic and Hanelt in this issue of Photochemistry and Photobiology describing the high-irradiance photophysiology of several strains of freshwater chlorophyte microalgal genus, Cosmarium. These strains exhibit distinct differences in how combined thermal- high irradiance stress is managed which can be related to the temperature and irradiance conditions of their native habitat.

Phytoplankton grow throughout the surface waters of the world's oceans and lakes, from warmest tropical seas to frigid melt ponds on polar sea ice. Survival in all these environments requires strategies to reduce high light stress on the photosynthetic apparatus. However, species use different strategies depending on the ambient water temperature. The thermal conditions in their native habitat govern which strategies are used by morphologically similar strains within one microalgal genus, even for cultures maintained for decades in moderate conditions. (image: global distribution of average sea surface temperature from NASA)

Nano sized defect pyrochlore, KAl_0.33W_1.67O₆ (KAW), is prepared through sol–gel method. Divalent tin-doped KAW is obtained at room temperature by ion exchange method using acidified SnCl₂ and parent KAW. These materials are characterized by powder X-ray diffraction, thermogravimetric analysis (TGA), scanning electron microscopy—energy dispersive spectra (SEM-EDS), Raman Spectroscopy and X-ray photo electronic spectroscopy. The composition of tin-doped KAW is obtained from chemical analysis, SEM-EDS and TGA methods and written as Sn_0.5Al_0.33W_1.67O₆ xH₂O (x = 1.4–1.5) (SnAW). It crystallizes in cubic lattice with space group. The band gap energies are found to be 2.82 and 2.21 eV for KAW and SnAW respectively. The observed reduction in the band gap with the introduction of Sn²⁺ in defect pyrochlore lattice is due to mixing of 5s state of Sn²⁺ with O 2p states leading to an upward shift in the valence band. The Raman spectra of these materials gave more bands than the number expected for defect pyrochlores due to substitutional disorder in 16c sites and displacive disorder of A ions. The photoactivity of SnAW is higher compared to KAW.

Using ion-exchange reaction of aqueous SnCl₂·2H₂O solution with KAl_0.33W_1.67O₆ (KAW) under ambient conditions Sn_0.5Al_0.33W_1.67O₆ (SnAW) was prepared. The band gap energies are found to be 2.82 and 2.21 eV for KAW and SnAW respectively. The observed reduction in the band gap with the introduction of Sn²⁺ in defect pyrochlore lattice is due to mixing of 5s state of Sn²⁺ with O2p states leading to an upward shift in the valence band.

During August 2011 stratospheric ozone over much of Southern Australia dropped to very low levels (approximately 265 Dobson Units) for over a week above major population centers. The weather during this low ozone period was mostly clear and sunny, resulting in measured solar ultraviolet radiation (UVR) levels up to 40% higher than normal, with UV Index > 3 despite being winter. Satellite ozone measurements and meteorological assimilated data indicate that the event was likely due in large part to the anomalous southward movement over Australia of ozone-poor air in the lower stratosphere originating from tropical latitudes. At the time, a study measuring the UVR exposures of outdoor workers in Victoria was underway and a number of the workers recorded substantial UVR exposures and were sunburnt. Given the cities and populations involved (approximately 10 million people), it is likely that many people could have been exposed to anomalously high levels of solar UVR for that time of year, with resultant higher UVR exposures and sunburns to unacclimatized skin (often a problem transitioning from low winter to higher spring UVR levels). Reporting procedures have been modified to utilize ozone forecasts to warn the public of anomalously high UVR levels in the future.

During August 2011, anomalous southward movement of stratospheric ozone-poor air from tropical latitudes resulted in very low ozone levels (approximately 265 Dobson Units) over much of Southern Australia. Consequently, measured solar ultraviolet radiation (UVR) levels increased by up to 40% higher than normal. Given the populations involved in the major cities there (approximately 10 million people), it is likely that many people could have resultant higher solar UVR exposures and sunburns. Reporting procedures have been modified to warn the public of unusually low ozone and high UVR levels in the future.

Ultraviolet germicidal irradiation (UVGI) for air disinfection applications has relied on low-pressure mercury vapor lamps for decades. New design requirements have generated the need for alternatives in some uses. This study describes the current state of UVGI technology and describes future directions for technology development, including the use of lamps produced from nontoxic materials and light-emitting diode lamps. Important applications are discussed such as the use of ultraviolet germicidal lamps in developing countries, in heating, ventilating and air-conditioning systems to improve energy efficiency and indoor air quality, and for whole room disinfection.

Ultraviolet germicidal irradiation (UVGI) for air disinfection applications has relied on low-pressure mercury vapor lamps for decades. New design requirements have generated the need for alternatives in some uses. This study describes the current state of UVGI technology and describes future directions for technology development, including the use of lamps produced from nontoxic materials and light-emitting diode lamps. Important applications are discussed such as the use of ultraviolet germicidal lamps in developing countries, in heating, ventilating and air-conditioning systems to improve energy efficiency and indoor air quality, and for whole room disinfection.

This study assessed the UVR protection provided by shade structures over toddler pools at swimming pool centers in Melbourne. The UVR protection was measured using a combination of UV sensitive polysulfone film to derive an average value during the middle of the day (1–2 P.M.) and handheld UV meters to derive the time variability in UV protection between 11 A.M. and 3 P.M. The amount of UVR protection provided by the shade structures depended upon a number of factors such as location, size, and materials used, but generally ranged from a protection factor (PF) of 2 to ~ 16. The higher PFs were generally for larger structures or where the shade had other structures nearby. The handheld UV meter measurements showed the UV protection varied with position under the shade structure as well as with time of day. While provision of shade structures is becoming more widespread around Australia, improving the shade availability at the pool centers overall, the application of recommendations regarding the provision of shade has been followed to a varying degree by many of the pools visited in this study. In many cases, continued further improvements can be made to provide more adequate protection and further reduce UV exposures.

This study assessed the UVR protection provided by shade structures over toddler pools at swimming pool centers in Melbourne, Australia using both UV sensitive film and handheld UV meters. The UV meter measurements showed the UV protection varied with position under the shade structure as well as with time of day. The UVR protection provided by the shade structures depended on factors such as location, size, and materials used and ranged from a protection factor (PF) of 2 to ca 16 for larger structures. Improvements to provide adequate protection and further reduce UV exposures are required and recommended.

This research evaluates a smartphone complementary metal oxide semiconductor (CMOS) image sensor's ability to detect and quantify incident solar UVA radiation and subsequently, aerosol optical depth at 340 and 380 nm. Earlier studies revealed that the consumer grade CMOS sensor has inherent UVA sensitivities, despite attenuating effects of the lens. Narrow bandpass and neutral density filters were used to protect the image sensor and to not allow saturation of the solar images produced. Observations were made on clear days, free from clouds. The results of this research demonstrate that there is a definable response to changing solar irradiance and aerosol optical depth can be measured within 5% and 10% error margins at 380 and 340 nm respectively. The greater relative error occurs at lower wavelengths (340 nm) due to increased atmospheric scattering effects, particularly at higher air masses and due to lower signal to noise ratio in the image sensor. The relative error for solar irradiance was under 1% for observations made at 380 nm. The results indicate that the smartphone image sensor, with additional external narrow bandpass and neutral density filters can be used as a field sensor to evaluate solar UVA irradiance and aerosol optical depth.

An enlarged image taken of the sun using the LG Optimus smartphone camera at a wavelength of 380 nm. The image was achieved using attached narrowband and neutral density filters. The grayscale response can be used to determine the solar irradiance and aerosol optical depth with a high level of accuracy when compared with the readings obtained from a Microtops II sunphotometer.

We evaluated six UV nail lamps representative of major US manufacturers to evaluate radiant hazards as defined in ANSI/IESNA RP-27 Recommended Practice for Photobiological Safety. Lamps were evaluated at three positions, 1 cm above the inner surface approximating exposure to the hand and the 20 cm RP-27 non-general light source distance, oriented normal and 45° to the opening. Hazard to skin at intended use distance classified these devices into Risk Group 1 or 2 (Low to Moderate) with S(λ) weighted Actinic UV ranging 1.2–1.7 μW cm⁻² and 29.8–276.25 min permissible daily exposure. At 20 cm on center and 45° UV risk to skin and eyes were all within Exempt classification. Actinic UV ranged 0.001–0.078 μW cm⁻² and unweighted near UV (320–400 nm) ranged 0.001–0.483 mW cm⁻². Likewise the retinal photochemical blue light hazard and retinal thermal and cornea/lens IR were also Exempt. One device had aphakic eye hazard slightly rising into Risk Group 1 (Low). There were no other photobiological risks to normal individuals. Total exposure following programmed times and steps accumulate to only a small fraction of RP-27 permissible daily occupational exposure. These risks are further mitigated in realistic nonoccupational use scenarios as it is unlikely to be a daily occurrence.

We subjected six US-manufactured UV nail lamps to ANSI/IESNA RP-27 Photobiological Safety evaluation. Spectra were measured at three positions, 1 cm above the inner surface to approximate hand exposure and 20 cm normal and 45° to the opening. Interior UV levels classified these lamps into Risk Group 1-Low or 2-Moderate with permissible daily exposure limits ranging 29–276 min. At 20 cm, photobiological risks to skin and eyes of normal individuals were within Exempt classification. Total programmed exposure steps accumulate to only a small fraction of permissible daily exposure. Realistic risks are further mitigated because expected use is less frequent.

A portable “fiber optic-based sensitizer delivery” (FOSD) device has been developed and studied. Before there might be success in photodynamic therapy (PDT) and antibacterial ambitions, an understanding of basic factors on device performance was needed. Thus, the device was examined for the localized delivery of sensitizer molecules in ovarian cancer cells and production of high concentrations of singlet oxygen for their eradication in vitro. The device tip releases stored pheophorbide by attack of singlet oxygen from sensitized oxygen gas delivered through the hollow fiber using 669 nm laser light. The performance of the device was enhanced when configured with a fluorosilane tip by virtue of its Teflon-like property compared with a conventional glass tip (greater sensitizer quantities were photoreleased and laterally diffused, and greater amounts of ovarian OVCAR-5 cancer cells were killed). No cell damage was observed at 2.2 N of force applied by the probe tip itself, an amount used for many of the experiments described here.

A portable “FOSD” device was developed and examined for the localized delivery of sensitizer molecules in ovarian cancer cells and production of singlet oxygen for their eradication in vitro. The device tip releases stored pheophorebide by attack of singlet oxygen from sensitized oxygen gas delivered through the hollow fiber using 669 nm laser light. Development of a sensitizer and singlet oxygen delivery device would be useful not only for cancer cell treatment, but also for bacteria, in cases where local delivery might be advantageous.

Attachment of bacteria to surfaces and subsequent biofilm formation remains a major cause of cross-contamination capable of inducing both food-related illness and nosocomial infections. Resistance to many current disinfection technologies means facilitating their removal is often difficult. The aim of this study was to investigate the efficacy of 405 nm light for inactivation of bacterial attached as biofilms to glass and acrylic. Escherichia coli biofilms (10³–10⁸ CFU mL⁻¹) were generated on glass and acrylic surfaces and exposed for increasing times to 405 nm light (5–60 min) at ca 140 mW cm⁻². Successful inactivation of biofilms has been demonstrated, with results highlighting complete/near-complete inactivation (up to 5 log₁₀ reduction on acrylic and 7 log₁₀ on glass). Results also highlight that inactivation of bacterial biofilms could be achieved whether the biofilm was on the upper “directly exposed” surface or “indirectly exposed” underside surface. Statistically significant inactivation was also shown with a range of other microorganisms associated with biofilm formation (Staphylococcus aureus, Pseudomonas aeruginosa and Listeria monocytogenes). Results from this study have demonstrated significant inactivation of bacteria ranging from monolayers to densely populated biofilms using 405 nm light, highlighting that with further development this technology may have potential applications for biofilm decontamination in food and clinical settings.

Microbial biofilms remain a major source of cross-contamination in both food and clinical environments. This study investigates the efficacy of 405 nm light (ca 140 m Wcm⁻²) for biofilm decontamination. Successful inactivation of Escherichia coli biofilms (10³–10⁷ CFU mL⁻¹) was demonstrated. Inactivation of Staphylococcus aureus, Pseudomonas aeruginosa and Listeria monocytogenes monolayer biofilms, and mixed-species biofilms (S. aureus and E. coli) was also shown. Results highlight that indirect exposure to 405 nm light can successfully inactivate biofilms: antimicrobial activity is retained when transmitted through transparent materials [glass(left)/acrylic(right)]. With further development, this technology may have potential use for practical biofilm decontamination applications.

The dynamics simulation and quantum chemical calculation are employed to investigate spectrum properties of deprotonation process of coelenteramide and two final states neutral state and phenolate anion. According to the calculation results, theoretical evidence supporting the luminescence mechanism hypothesis is proposed in a significant bioluminescence process. In vivo of marine bioluminescent organisms, if the protein motion provides the conditions for the deprotonation of coelenteramide in some protein molecules, the phenolate anion is completely deprotonated coelenteramide as an emitter in these protein molecules and emits fluorescence assigned to the lower energy peak. And in another emitter in which the condition of deprotonation is not met, the fluorescence is produced by the neutral state of coelenteramide and assigned to the higher energy peak. The energy difference decreases gradually when the proton of coelenteramide gradually approaches to His22. For phenolate anion and neutral state, electronic cloud distributions between their each frontier molecular orbitals HOMO and LUMO have high overlapping volume. The molecular electrostatic potential indicates that for phenolate anion, the oxygen atom after deprotonation has greater electron density, which is good for formation hydrogen bonds with amino acids in the environment.

The fluorescence wavelength is determined by emitter state, which depends on whether or not the protein motion provides the condition for the deprotonation of substrate in protein molecules. If the His22 is protonated, the emitter is phenolate anion as proton donor. If the hydrogen abstraction reaction occurs, the substrate as emitter is neutral state. The dynamics simulation and quantum chemical calculation are employed to investigate spectrum properties of deprotonation process of coelenteramide and two final states neutral state and phenolate anion.

Mitochondrial-targeting photosensitizers have been associated with effective photodynamic responses. However, most photosensitizers absorb light between 400 and 700 nm, where light penetration through tissues is limited. Two-photon excitation is a rational approach to improve light penetration through tissues. In this report, the two-photon photophysical properties of a porphyrin–rhodamine B conjugate (TPP-Rh), previously demonstrated to target the mitochondria, were evaluated. The properties studied included: two-photon absorption (TPA) cross sections (σ₂); resonance energy transfer (RET) kinetics and dynamics; and singlet oxygen generation. The conjugation of Rh B to TPP-OH approximately doubled the σ₂ of TPP-Rh at 800 nm (40 ± 4 GM) compared with the parent porphyrin, TPP-OH (16 ± 4 GM). Furthermore, the rate of DPBF oxidation by singlet oxygen generated from TPP-Rh was twice as fast compared with that from TPP-OH (73 % versus 33% in 10 min) following two-photon excitation at 800 nm. In addition, a significantly stronger luminescence signal was detected from TPP-Rh, than from TPP-OH at 1270 nm, following two-photon excitation. This study indicates that conjugating photosensitizers to Rh B could provide greater TPA at the near-infrared range in addition to preferential mitochondrial accumulation for improved photodynamic responses.

The two-photon photophysical properties of a porphyrin–rhodamine B conjugate (TPP-Rh), previously demonstrated to target the mitochondria, were evaluated such as TPA cross sections (σ₂), RET kinetics, dynamics and singlet oxygen generation. Approximately doubled σ₂ of TPP-Rh (40 ± 4 GM) compared with its parent porphyrin (16 ± 4 GM) was measured. Furthermore, TPP-Rh produced singlet oxygen at a significantly faster rate than its parent porphyrin. This study indicates that conjugating photosensitizers to Rh B could provide greater TPA at near-infrared range.

Photohydrates are formed in high yield when uridine (Urd), 2′-deoxyuridine (dUrd), cytidine (Cyd) and 2′-deoxycytidine (dCyd) are irradiated with UVC in aqueous solution. The thermal reactions of the photohydrates of Urd with amines at pH values near pH 7.5 have been studied using UV spectroscopy, HPLC, mass spectrometry and, in some cases, NMR. It has been found that a number of amines (i.e. ethylenediamine, N,N′-dimethylethylenediamine, glycine, glycinamide, glycylglycine, glycylgylcylglycine, putrescine, spermidine and spermine) react thermally with such hydrates to form products with UV spectra characteristic of opened ring uridine-amine adducts. In general, these products display a strong absorption peak with λ_max in the range between 288 and 310 nm. Mass spectral studies of a number of the products indicate that they contain one molecule of parent nucleoside and one molecule of reactant amine. Upon standing in water these products revert to parent hydrate, while heating produces parent nucleoside. Less comprehensive studies indicate that photohydrates of dUrd and dCyd undergo analogous thermal reactions. Preliminary results suggest that UV-irradiated polyuridylic acid and polycytidylic acid undergo similar reactions. These results may have relevance for obtaining a complete understanding of the biological effects of producing Urd and dCyd photohydrates in a cellular environment.

Photohydrates are produced when uridine (Urd), 2′-deoxyuridine and 2′-deoxycytidine are irradiated with UVC in aqueous solution. We have found that such photohydrates undergo thermal reactions with several amines (e.g. spermine, spermidine, glycylglycine, ethylenediamine and glycine amide) at near neutral pH values to yield nucleoside-amine adducts, as displayed in the figure for the Urd hydrate (shown in one epimeric form). In general, these products display a strong absorption peak with λ_max in the range between 288 and 310 nm. The Urd-amine adducts are reasonably stable in frozen aqueous solution, but revert to Urd hydrates upon standing in liquid water.

The photoinduced mechanism of formation of mono- and diadducts between 8-MOP and thymine bases is studied using the ONIOM(MPWB1K/6–31 + G(d,p):B3LYP/6–31G(d,p):UFF) and B3LYP/6–31 + G(d,p) methods. The relevant cycloaddition displays favorable energy barriers and reaction energies in the triplet excited state, which involves the initial formation of a diradical followed by ring closure via singlet–triplet interaction. The monoadduct on the pyrone side is favored over the furan side when comparing reaction energies. The distinguishing feature in the formation of the monoadducts is that the furan-side adduct displays a better photostability, which is a relatively high-barrier exothermic reaction, and thus the energy balance of the monoadduct on the furan side toward final diadduct formation is favored.

The photoreaction of 8-MOP and thymine bases was studied by DFT. The monoadduct on the pyrone side is favored over the furan side when comparing reaction energies. The distinguishing feature is that the furan-side monoadduct displays a better photostability, which is a relatively high-barrier exothermic reaction, and thus the energy balance of the monoadduct on the furan side toward final diadduct formation is favored.

The successful implementation of photodynamic therapy (PDT)-based regimens depends on an improved understanding of the dosimetric and biological factors that govern therapeutic variability. Here, the kinetics of tumor destruction and regrowth are characterized by systematically varying benzoporphyrin derivative (BPD)-light combinations to achieve fixed PDT doses (M × J cm⁻²). Three endpoints were used to evaluate treatment response: (1) Viability evaluated every 24 h for 5 days post-PDT; (2) Photobleaching assessed immediately post-PDT; and (3) Caspase-3 activation determined 24 h post-PDT. The specific BPD-light parameters used to construct a given PDT dose significantly impact not only acute cytotoxic efficacy, but also treatment durability. For each dose, PDT with 0.25 μM BPD produces the most significant and sustained reduction in normalized viability compared to 1 and 10 μM BPD. Percent photobleaching correlates with normalized viability for a range of PDT doses achieved within BPD concentrations. To produce a cytotoxic response with 10 μM BPD that is comparable to 0.25 and 1 μM BPD a reduction in irradiance from 150 to 0.5 mW cm⁻² is required. Activated caspase-3 does not correlate with normalized viability. The parameter-dependent durability of outcomes within fixed PDT doses provides opportunities for treatment customization and improved therapeutic planning.

The photosensitizer-light parameters used to construct a photodynamic therapy (PDT) dose significantly impact tumor destruction and regrowth kinetics. A 3D ovarian cancer model (a) is used to evaluate a matrix of benzoporphyin derivative (BPD) and light combinations for three fixed PDT doses (b). PDT with 0.25 μM BPD (blue) provides maximum cytotoxic durability for all doses (c). Representative LIVE/DEAD (green/red) images (d) that were used to generate normalized viabilities in (c), depict increased killing in nodules treated with 0.25 μM BPD-PDT (2) compared to PDT with 1 μM (3) or 10 μM (4) BPD. These findings suggest that customization of PDT parameters could improve treatment outcomes.

The inactivation of pathogenic aerosols by solar radiation is relevant to public health and biodefense. We investigated whether a relatively simple method to calculate solar diffuse and total irradiances could be developed and used in environmental photobiology estimations instead of complex atmospheric radiative transfer computer programs. The second-order regression model that we developed reproduced 13 radiation quantities calculated for equinoxes and solstices at 35^° latitude with a computer-intensive and rather complex atmospheric radiative transfer program (MODTRAN) with a mean error <6% (2% for most radiation quantities). Extending the application of the regression model from a reference latitude and date (chosen as 35° latitude for 21 March) to different latitudes and days of the year was accomplished with variable success: usually with a mean error <15% (but as high as 150% for some combination of latitudes and days of year). This accuracy of the methodology proposed here compares favorably to photobiological experiments where the microbial survival is usually measured with an accuracy no better than ±0.5 log₁₀ units. The approach and equations presented in this study should assist in estimating the maximum time during which microbial pathogens remain infectious after accidental or intentional aerosolization in open environments.

This study describes a relatively simple method to calculate solar diffuse and total irradiances for using in environmental photobiology estimations instead of complex atmospheric radiative transfer computer programs. The model reproduced calculations for equinoxes and solstices at 35° latitude made by a computer-intensive and rather complex atmospheric radiative transfer program (MODTRAN) with a mean error <6%. The overall accuracy obtained by the regression model presented is usable in most radiative transfer scenarios found in the atmosphere. The approach and equations presented in this study should assist in estimating the maximum time during which microbial pathogens remain infectious after accidental or intentional aerosolization in open environments.

This study is designed to investigate the chemopreventive effect and molecular mechanisms of α-santalol on UVB-induced skin tumor development in SKH-1 hairless mouse, a widely used model for human photocarcinogenesis. A dose of UVB radiation (30 mJ cm⁻² day⁻¹) that is in the range of human sunlight exposure was used for the initiation and promotion of tumor. Topical treatment of mice with α-santalol (10%, wt/vol in acetone) caused reduction in tumor incidence, multiplicity and volume. In our study, the anticarcinogenic action of α-santalol against UVB-induced photocarcinogenesis was found to be associated with inhibition of inflammation and epidermal cell proliferation, cell cycle arrest and induction of apoptosis. α-Santalol pretreatment strongly inhibited UVB-induced epidermal hyperplasia and thickness of the epidermis, expression of proliferation and inflammation markers proliferating cell nuclear antigen (PCNA), Ki-67 and cyclooxygenase 2 (Cox-2). Significant decrease in the expression of cyclins A, B1, D1 and D2 and cyclin-dependent kinases (Cdk)s Cdk1 (Cdc2), Cdk2, Cdk4 and Cdk6 and an upregulated expression of cyclin-dependent kinase (CDK) inhibitor Cip1/p21 were found in α-santalol pretreated group. Furthermore, an elevated level of cleaved caspase 3 and cleaved poly (ADP-ribose) polymerase (PARP) were observed in α-santalol-treated group. Our data suggested that α-santalol is a safer and promising skin cancer chemopreventive agent with potential to target various pathways involved in photocarcinogenesis.

Topical treatment of SKH-1 hairless mice with α-santalol, a terpenoid isolated from santalum tree, caused reduction in tumor incidence, multiplicity and volume in UVB-induced skin carcinogenesis. In this study, the anticarcinogenic action of α-santalol against UVB-induced photocarcinogenesis was found to be associated with inhibition of inflammation and epidermal hyperplasia, cell cycle arrest and induction of apoptosis. Our results suggest that α-santalol is a safer and promising skin cancer chemopreventive agent with potential to target various pathways involved in photocarcinogenesis.

In upper-room ultraviolet germicidal irradiance (UVGI) design, irradiance is an important characteristic, with two opposing dominant dynamics: high-level irradiation on the microorganism and minimum levels of irradiance on human skin and eyes. The use of high-level ray-tracing procedures is followed in establishing radiance and irradiance levels. The main constants in a room influencing these calculations are the spectral and spatial characteristics of the radiation sources in the inter-reflecting surfaces inside the luminaire, as well as the surfaces in the room. The most important characteristic to be determined for the radiation source prior to calculations is its spatial radiant intensity distribution. This characterization is performed using a gonioradiometer. The complexity of the physical construction of the luminaire will determine the extent to which measurements have to be taken. Accurate gonioradiometer readings provide the required radiant intensities in all directions for computer-aided design (CAD), and can also be used to determine the total radiant flux leaving the luminaire, as well as calculating isoirradiance surfaces around the UVGI luminaire. This study will present a laboratory experimental approach to deriving the radiant intensity distribution of a UVGI luminaire. The UVGI luminaire is then characterized in situ, and compared with the gonioradiometric output.

Upper-room Ultraviolet Germicidal Irradiation (UVGI) is commonly used as an environmental control measure to minimize the risk of transmission of airborne pathogens. Characterizing UVGI luminaires, in a laboratory and in situ, is essential in understanding the radiant intensity distributions delivered by the same designed luminaire, operating under different conditions. This understanding may be used in future design applications, such as computer-aided design (CAD), to calibrate the difference in behavior of luminaires between laboratory and in situ scenarios.

The photoproducts from reaction of thymine with cysteine, an amino acid containing a sulfhydryl group, have been studied in detail, whereas results of less extensive studies have been reported for the uracil–cysteine system. However, products arising from corresponding reactions of cytosine and related compounds with compounds containing a sulfhydryl group have not been similarly studied. We report here the results of our study of the photoreaction of 5-methylcytosine (5MeCyt), a minor base occurring in mammalian DNA, with 3-mercaptopropionic acid (3MP), a model compound for cysteine. We found that this reaction proceeds at pH 7 to yield N-(N'-(2′-carboxyethyl)thiocarbamoyl)-3-amino-2-methylacrylamidine (Ia) as a primary photoproduct. A secondary thermal product, identified as 3-(2′-carboxyethylthio)-2-methylacrylamidine (IIa), appears if photoreacted solution is allowed to stand for appreciable times prior to workup; this latter compound is formed via an intermediate product. Heating of purified Ia at 100°C or standing at lower temperatures produces 3-amino-2-methylacrylamidine (IId); similarly, irradiation of Ia with UVB light in aqueous solution converts it into IId. Results from exploratory studies suggest that 5MeCyt similarly reacts with other thiols (2-mercaptoethanol, 2-mercaptoacetic acid) to form analogs of Ia and IIa. Other preliminary results suggest that 5-methyl-2′-deoxycytidine and 1,5-dimethylcytosine photoreact with 3MP to form compounds similar to Ia.

The photoreactions of 5-methylcytosine (5MeCyt), a minor base contained in eukaryotic DNA, with several cysteine analogs have been studied. The reaction of 5MeCyt with 3-mercaptopropionic acid (3MP) is shown schematically in the accompanying Figure. Irradiation with UVB light produces the opened-ring adduct Ia. Upon standing at ambient temperature in the presence of 3MP, the product IIa appears in solution. The latter reaction proceeds via a closed-ring intermediate that has been characterized using UV spectroscopy, proton NMR spectrometry and mass spectrometry. Either heating or irradiation of purified Ia with UVB light in aqueous solution converts it into 3-amino-2-methylacrylamidine.

The exposure of DNA to ultraviolet (UV) radiation causes sequence-dependent damage. Thus, there is a need for an analytical technique that can detect damage in large numbers of DNA sequences simultaneously. In this study, we have designed an assay for UVC-induced DNA damage in multiple oligonucleotides simultaneously by using a 96-well plate and a novel automated sample mover. The UVC-induced DNA damage is measured using smart probes, analogs of molecular beacons in which guanosine nucleotides act as the fluorescence quencher. Our results show that the oligonucleotide damage constants obtained with this method are reproducible and similar to those obtained in cuvettes. The calibration curve for poly-dT shows good linearity (R² = 0.96), with limits of detection (LOD) and quantification (LOQ) equal to 55 and 183 nm, respectively. The results show that the damage kinetics upon irradiation is sensitive to the different types of photoproducts formed in the different sequences used; i.e. poly-A oligonucleotides containing guanine are damaged at a faster rate than poly-A oligonucleotides containing either thymine or cytosine. Thus, detecting DNA damage in a 96-well plate and quantifying the damage with smart probes are a simple, fast and inexpensive mix-and-read technique for multiplexed, sequence-specific DNA damage detection.

A 96-well microplate is developed here as a platform for the detection of DNA damage in a number of DNA sequences simultaneously. This convenient mix-and-read assay uses smart probes, a hybridization assay composed of fluorescently labeled ssDNA hairpins complementary to the damaged target sequences, as general probes of DNA damage. The results show that the 96-well microplate platform is a simple, fast and inexpensive mix-and-read technique for multiplexed, sequence-specific DNA damage detection.

This research was conducted to evaluate the design of hospital ultraviolet germicidal irradiation (UVGI) systems and to assess their effectiveness for inactivating airborne mycobacteria. A computational fluid dynamics (CFD) model was developed and tested by simulating previous experiments measuring the effectiveness of a lab-based UVGI system. Model testing showed reasonable agreement with experimental measurements. The model captured trends similar to the experiments: Effectiveness of an upper-room UVGI system is higher when there is no ventilation compared with when there is ventilation, and wintertime ventilation conditions can markedly decrease the performance of an upper-room UVGI system. The CFD model was then applied to evaluate the design of three hospital patient rooms. A patient and an exam room with upper-room UVGI systems, and a patient room with an exhaust duct system were studied. Results showed that one of the UVGI systems was not very effective, due to the very efficient ventilation design. The other two configurations were reasonably to very effective at inactivating airborne mycobacteria. The most effective application was the one in which the room air-exchange rate was very low. CFD modeling can be useful for assessing whether hospital UVGI installations and ventilation systems are effective for infection control.

As part of their infection control strategy, hospitals use upper-room ultraviolet germicidal irradiation (UVGI) systems to inactivate airborne infectious agents. A computational fluid dynamics model was developed and applied to evaluate the design of the three hospital rooms, a patient and exam room with upper-room systems and a patient room with an exhaust duct system. One of the UVGI systems was not very effective, due to efficient ventilation design. The other two configurations were effective at inactivating airborne mycobacteria. The most effective application was the one for which the room air-exchange rate was very low.

We determined the sensitivity of Pseudomonas aeruginosa to direct sunlight radiation, while maintaining the experimental temperature below levels harmful to the bacterium. The results presented here were similar to previous data on solar sensitivity obtained half a world away on another related bacterial species. The findings presented in this study suggest that related bacteria have a characteristic sensitivity to sunlight with their survival depending mainly on the fluence (photons) received in a dose-dependent manner that is otherwise relatively independent from latitude, atmospheric ozone and other local conditions. Conditions that inactivated P. aeruginosa did not result in measurable impairment of specific polymerase chain reaction (PCR) or enzyme-linked immunoassays (ELISA) tests suggesting that this germ could still be amenable to detection after inactivation by sunlight. The results presented in this study should assist in predicting the survival of P. aeruginosa outdoors and in monitoring the risk posed by this widespread organism in a variety of environmental settings.

This study suggest that related bacteria have a characteristic sensitivity to sunlight with their survival depending mainly on the fluence (photons) received in a dose-dependent manner that is otherwise relatively independent from latitude, atmospheric ozone and other local conditions. Conditions that inactivated P. aeruginosa did not result in measurable impairment of specific PCR or ELISA tests suggesting that this germ could still be amenable to detection after inactivation by sunlight. The results presented in this study should assist in predicting the survival of P. aeruginosa outdoors and in monitoring the risk posed by this widespread organism in a variety of environmental settings.

The ultraviolet (UV) absorption of various sections of the human lens was studied and compared with protein expression paralleling differential UV absorbance in anterior and posterior lenticular tissue. The UV absorbance of serial lens cryostat sections (60 μm) and that of lens capsules was determined using a Shimadzu scanning spectrophotometer, and the absorption coefficients were calculated. Two-dimensional gel electrophoresis was performed using two pooled lenticular protein extracts (anterior and posterior sections). Protein spots were quantified and significantly different spots were identified by mass spectrometry following in-gel digestion with trypsin and chymotrypsin. The UV-C and UV-B absorption of the human lens increased toward the posterior parts of the lens. The anterior and posterior lens capsules also effectively absorbed UV radiation. Levels of molecular chaperone proteins Beta-crystallin B2 (UniProtKB ID:P43320), A3 (UniProtKB ID:P05813) and of glyceraldehyde 3-phosphate dehydrogenase (UniProtKB ID:P04406) were significantly higher in the anterior part of the lens, whereas lens proteins Beta-crystallin B1 (UniProtKB ID:P53674) and Alpha-crystallin A chain (UniProtKB ID:P02489) were higher in the posterior sections. These results provide evidence that differential UV absorption in the anterior and posterior lens is accompanied by differential protein expression.

Although the cornea absorbs most of the ultraviolet (UV) radiation, still considerable radiation may reach the lens. By measuring the UV absorption of human lens sections we found that the UV-C and UV-B absorption of the human lens increased toward the posterior parts of the lens. Two-dimensional gel electrophoresis and mass spectroscopy analysis identified significantly different protein spots in the anterior and posterior section pools. Beta-crystallin B2 and A3 along with glyceraldehyde 3-phosphate dehydrogenase were enriched in the anterior part of the lens while elevated levels of Alpha-crystallin A chain and Beta-crystallin B1 proteins were found in the posterior portion.

Ultraviolet (UV) radiation damages human skin and causes skin diseases such as epidermal hyperplasia, sunburn, inflammatory responses and photoaging. Photoaging is associated with upregulated matrix metalloproteinase (MMP) expression and downregulated collagen synthesis. Fucosterol, which is isolated from marine brown algae, has been reported to possess antioxidant and anticancer activities; however, its effects on photoaging are unknown. This study assessed the effects of fucosterol on photoaging and investigated its mechanisms of action in UV-irradiated immortalized human keratinocytes (HaCaT) by enzyme-linked immunosorbent assay, semi-quantitative reverse transcription-polymerase chain reaction, Western blot analysis and 2′,7′-dichlorofluorescein diacetate assay. Our results showed that fucosterol attenuated UV-induced MMP and inflammatory cytokine expression by deactivating mitogen-activated protein kinases (MAPKs) induced by reactive oxygen species. Fucosterol also increased type-I procollagen and antioxidant enzyme expression. Taken together, fucosterol regulates the expression of MMPs and type-I procollagen in UV-irradiated HaCaT by modulating MAPK, suggesting it as a potential candidate for prevention and treatment of skin aging.

Activated MMP-1, which is a member of the collagenase subfamily of MMPs, initiates collagen breakdown by cleaving type I and type III collagen, which are further degraded by MMP-2 and -9. Fucosterol reduced UV-irradiated MMP-1 production by 7% at 0.5 µm, 23% at 1 µm, and 38% at 5 µm compared with the UV-induced control. The results suggest that fucosterol could be a potential anti-photoaging agent via downregulation of MMP expression.

Metabolic syndrome is characterized by hyperglycemia, hypertension, dyslipidemia and obesity. Diabetes and hypertension are the main causes of chronic end-stage kidney disease in humans. Chronic kidney disease is characterized by kidney inflammation and eventual development of kidney fibrosis. Low-level laser (or light) therapy (LLLT) can be used to relieve pain associated with some inflammatory diseases due to photochemical effects. Despite the known contribution of inflammation to metabolic syndrome and kidney disease, there is scarce information on the potential therapeutic use of LLLT in renal disease. The aim of this randomized, placebo-controlled study was to test the hypothesis that LLLT could modulate chronic kidney injury. Rats with nephropathy, hypertension, hyperlipidemia and type II diabetes (strain ZSF1) were subjected to three different conditions of LLLT or sham treatment for 8 weeks, and then sacrificed 10 weeks later. The main findings of this study are that the LLLT-treated rats had lower blood pressure after treatment and a better preserved glomerular filtration rate with less interstitial fibrosis upon euthanasia at the end of follow-up. This initial proof-of-concept study suggests that LLLT may modulate chronic kidney disease progression, providing a painless, noninvasive, therapeutic strategy, which should be further evaluated.

Low-Level Laser Therapy (LLLT) reduces loss of renal function in rat model of progressive chronic kidney injury induced by spontaneous metabolic syndrome. The laser treatment improved the glomerular filtration rate (GFR) and decreased the interstitial fibrosis.

Recently, we have proposed that the fluorescence spectra of sheep retina can be well correlated with the presence or absence of scrapie. Scrapie is the most widespread TSE (transmissible spongiform encephalopathy) affecting sheep and goats worldwide. Mice eyes have been previously reported as a model system to study age-related accumulation of lipofuscin, which has been investigated by monitoring the increasing fluorescence with age covering its entire life span. The current work aims at developing mice retina as a convenient model system to diagnose scrapie and other fatal TSE diseases in animals such as sheep and cows. The objective of the research reported here was to determine whether the spectral features are conserved between two different species namely mice and sheep, and whether an appropriate small animal model system could be identified for diagnosis of scrapie based on the fluorescence intensity in retina. The results were consistent with the previous reports on fluorescence studies of healthy and scrapie-infected retina of sheep. The fluorescence from the retinas of scrapie-infected sheep was significantly more intense and showed more heterogeneity than that from the retinas of uninfected mice. Although the structural characteristics of fluorescence spectra of scrapie-infected sheep and mice eyes are slightly different, more importantly, murine retinas reflect the enhancement of fluorescence intensity upon infecting the mice with scrapie, which is consistent with the observations in sheep eyes.

Scrapie is the most widespread transmissible spongiform encephalopathy (TSE) affecting sheep and goats worldwide. The current work aims at developing mice retina as a convenient model system to diagnose scrapie and other fatal TSE diseases in animals such as sheep and cows. Steady-state fluorescence and hyperspectral imaging has been used as tools to investigate the fluorescence from the retinas of scrapie-infected mice and compared with those of healthy (uninfected) control mice. The fluorescence from the retinas of scrapie-infected mice was significantly more intense and showed more heterogeneity than that from the retinas of uninfected mice.

Bi₂WO₆ and Bi₂WO₆–TiO₂ (5% molar Ti) nano-heterostructures were synthesized by a hydrothermal method. The properties of the synthesized catalysts were characterized, having high photoactivity for Rhodamine B degradation under sun-like illumination, explained by a synergetic mechanism previously proposed through UV and visible induced processes, in which the photosensitization effect of Rhodamine B is considered. We now report that using Phenol, a molecule which does not lead the photosensitization process, the photoactivity decreased considerably, thus emphasizing how important is the model molecule selected as degradation substrate for evaluating the photoactivity. The photocatalytic properties of the synthesized catalysts have been evaluated by exposing a mixture of Rhodamine B and Phenol in water, to different illumination conditions. It can be confirmed that the photoinduced mechanism via the photosensitization of Rhodamine B is a key factor responsible for the increase on the photocatalytic activity showed by the Bi₂WO₆–TiO₂ compound and that the degradation mechanism of Rhodamine B is not changed by the simultaneous presence of other transparent substrate as Phenol.

Bi₂WO₆ and Bi₂WO₆–TiO₂ were synthesized by hydrothermal method and evaluated in the photodegradation of Rhodamine B/Phenol mixtures with two illumination conditions. Previous studies revealed that these materials were very effective in Rhodamine B degradation by the influence of a mixed photocatalytic and photosensitized mechanism. In this work, it is demonstrated that when a molecule with no influence of photosensitization as Phenol is used as substrate, the photoactivity considerably decreases and that the photoinduced mechanism via Rhodamine B photosensitization is a key factor in the increased activity of this kind of materials.

This study investigated the disinfection efficacy of the upper-room ultraviolet germicidal irradiation (UR-UVGI) system with ceiling fans. The investigation used the steady-state computational fluid dynamics (CFD) simulations to solve the rotation of ceiling fan with a rotating reference frame. Two ambient air exchange rates, 2 and 6 air changes per hour (ACH), and four downward fan rotational speeds, 0, 80, 150 and 235 rpm were considered. In addition, the passive scalar concentration simulations incorporated ultraviolet (UV) dose by two methods: one based on the total exposure time and average UV fluence rate, and another based on SVE3* (New Scale for Ventilation Efficiency 3), originally defined to evaluate the mean age of the air from an air supply opening. Overall, the CFD results enabled the evaluation of UR-UVGI disinfection efficacy using different indices, including the fraction of remaining microorganisms, equivalent air exchange rate, UR-UVGI effectiveness and tuberculosis infection probability by the Wells–Riley equation. The results indicated that air exchange rate was the decisive factor for determining UR-UVGI performance in disinfecting indoor air. Using a ceiling fan could also improve the performance in general. Furthermore, the results clarified the mechanism for the ceiling fan to influence UR-UVGI disinfection efficacy.

Ceiling fans are considered an essential adjunct in the application of upper-room ultraviolet germicidal irradiation (UR-UVGI), especially in the resource-limited countries and areas. Numerical evaluation of UR-UVGI disinfection efficacy using TB infection probability by Wells–Riley equation indicated that air exchange rate was the decisive factor for determining UR-UVGI performance in disinfecting indoor air, and using a ceiling fan could improve the performance in general. The results also indicated the possibility of increasing the TB infection risk by using ceiling fan without effective air disinfection by ventilation or UR-UVGI.

Concerns about the safety of Ultraviolet Germicidal Irradiation (UVGI) applications on human beings have been an issue at least since the introduction of this technology for practical use in the 1930s. The resurgence of tuberculosis (TB) in the United States in the mid-1980s led to a revival of interest in UV technology, a focus that had almost disappeared because alternate means of controlling TB had inaccurately been deemed successful. These failures in TB control led to a revival of UVGI use. And with that revival grew necessary and appropriate concerns about attempts to eliminate human overexposure. For all those working in the field of UVGI, safety issues must be a concern because when UVGI fixtures are placed improperly, or precautions ignored, room occupants are placed at risk of photokeratoconjunctivitis and photodermatitis. If safety is so prominent a concern, why do incidents of UV side effects continue to occur? See Murphy's Law.

The resurgence of tuberculosis (TB) in the United States in the mid-1980s led to a revival of interest in upper-room UVGI air cleansing technology, a focus that had almost disappeared because alternate means of controlling TB had inaccurately been deemed successful. For all those working in the field of UVGI, safety issues must be a concern because when UVGI fixtures are placed improperly, or precautions ignored, room occupants are placed at risk of photokeratoconjunctivitis and photodermatitis. If safety is so prominent a concern, why do incidents of UV side effects continue to occur? See Murphy's Law.

This study outlines the potential for Computational Fluid Dynamics (CFD) simulation to be used to predict upper-room ultraviolet germicidal irradiation (UVGI) effectiveness to aid system design and the development of future guidance. A numerical study of two wall-mounted UVGI lamps in a mechanically ventilated test chamber is used to assess the influence of modeling parameters on prediction of dose distribution and microorganism inactivation. Irradiance fields for both UVGI fixtures are obtained via radiometry and implemented in the model. A series of sensitivity studies consider the importance of UVGI field accuracy and computational grid and turbulence model selection. Results show that 2D irradiance fields are sufficient for calculating dose and in-activation, whereas a 1D field is inadequate for modeling purposes. Further parametric studies consider the effects of ventilation parameters, UVGI lamp configuration and microorganism susceptibility. These demonstrate the feasibility of modeling the interaction of the airflow and UV field in a room to quantify the dose distribution. Microorganism in-activation can also be accomplished by employing passive scalars and species transport models, however, further validation data are necessary before this can be used to make reliable quantitative predictions.

Our work explores the potential of computer airflow simulation in predicting the performance of upper-room ultraviolet germicidal irradiation (UVGI) effectiveness. Experimentally measured irradiance fields are combined with Computational Fluid Dynamics (CFD) methodology to predict the dose distribution (J m⁻²) within a small mechanically ventilated room for a range of test conditions. A series of detailed sensitivity studies illustrate the importance of the numerical grid size, the turbulence model employed and the fidelity of the irradiance field. We demonstrate that a two-dimensional UV field is sufficient for modeling purposes and the resulting dose distribution offers valuable insight into predicted disinfection performance.

Non-B DNAs, which can form unique structures other than double helix of B-DNA, have attracted considerable attention from scientists in various fields including biology, chemistry and physics etc. Among them, i-motif DNA, which is formed from cytosine (C)-rich sequences found in telomeric DNA and the promoter region of oncogenes, has been extensively investigated as a signpost and controller for the oncogene expression at the transcription level and as a promising material in nanotechnology. Fluorescence techniques such as fluorescence resonance energy transfer (FRET) and the fluorescence quenching are important for studying DNA and in particular for the visualization of reversible conformational switching of i-motif DNA that is triggered by the protonation. Here, we review the latest studies on the conformational dynamics of i-motif DNA as well as the application of FRET and fluorescence quenching techniques to the visualization of reversible conformational switching of i-motif DNA in nano-biotechnology.

The i-motif DNA, which is formed from cytosine (C)-rich sequences at slightly acidic pH or even neutral pH, has been extensively investigated as a signpost and controller for the oncogene expression at the transcription level and as a promising material in nanotechnology. Using the fluorescence techniques such as FRET and the fluorescence quenching, thus, the visualization of the unique and reversible conformational switching of i-motif DNA triggered by the proton has been widely preformed for applying in the nanotechnology.

The excited states of UV absorber, ethylhexyl methoxycrylene (EHMCR) have been studied through measurements of UV absorption, fluorescence, phosphorescence and electron paramagnetic resonance (EPR) spectra in ethanol. The energy levels of the lowest excited singlet (S₁) and triplet (T₁) states of EHMCR were determined. The energy levels of the S₁ and T₁ states of EHMCR are much lower than those of photolabile 4-tert-butyl-4′-methoxydibenzoylmethane. The energy levels of the S₁ and T₁ states of EHMCR are lower than those of octyl methoxycinnamate. The weak phosphorescence and EPR B_min signals were observed and the lifetime was estimated to be 93 ms. These facts suggest that the significant proportion of the S₁ molecules undergoes intersystem crossing to the T₁ state, and the deactivation process from the T₁ state is predominantly radiationless. The photostability of EHMCR arises from the ³ππ* character in the T₁ state. The zero-field splitting (ZFS) parameter in the T₁ state is D** = 0.113 cm⁻¹.

The excited states of UV absorber, ethylhexyl methoxycrylene (EHMCR) have been studied through measurements of UV absorption, fluorescence, phosphorescence and electron paramagnetic resonance spectra in ethanol. The energy levels of the lowest excited singlet (S₁) and triplet (T₁) states of EHMCR were determined. The energy levels of the S₁ and T₁ states of EHMCR are much lower than those of photolabile 4-tert-butyl-4′-methoxydibenzoylmethane. The energy levels of the S₁ and T₁ states of EHMCR are lower than those of octyl methoxycinnamate.

Ag/SmVO₄ composite photocatalysts were synthesized and characterized by BET, XRD, Raman, SEM, TEM, XPS and DRS techniques. Their photocatalytic activities were determined by oxidative decomposition of RhB in aqueous solution under visible light irradiation. The charge separation efficiency was evaluated by the photocurrent-time and ֹOH-trapping experiments. The results revealed that the loaded Ag species greatly improved the efficiency in charge separation, and thus led to enhanced photocatalytic activities compared with that of the pure SmVO₄. The sample contained 0.5 wt% Ag and heated at 500°C presents the highest photoactivity.

The loaded Ag nanoparticles greatly promote the photocatalytic activity of SmVO₄ in the photodegradation of RhB solution. The Ag nanoparticles behave as the electron sink to enhance the separation of electron-hole pairs, which is the origin of the high activity and has been proven by the photocurrent and ֹOH-trapping experiments.

The ground-state equilibrium geometries, electronic structures and vertical excitation energies of methyl- and methoxyl-substituted phenol radical cations and phenoxyl radicals have been investigated using time-dependent density-functional theory (namely TD-B3LYP) and complete-active-space second-order perturbation theory (CASPT2). The “anomalous” large redshifts of the absorption maxima of the phenol radical species observed in the ultraviolet–visible spectral region upon di-meta-methoxyl substitution are reproduced by the calculations. Furthermore, these “anomalous” shifts which were unexplained to date can be rationalized on the basis of a qualitative molecular orbital perturbation analysis.

The main electronic transitions implicated in the observed ultraviolet–visible absorption spectra of phenol radical cations and phenoxyl radicals have been characterized by quantum-chemical calculations. The positions of the absorption bands predicted by time-dependent density-functional theory (TD-B3LYP) are found to be in good agreement with experimental data, and observed substituent effects are reproduced. Furthermore, a molecular orbital perturbation analysis unveils the relationship between the shift in excitation energy and the atomic contribution to the molecular orbitals implicated in the electronic transition at the substituent position, providing insight into the origin of the observed “anomalous” large redshifts observed for 3,5-dimethoxyl substitution.

A photocatalytic reactor with UV/TiO₂ was used for the posttreatment of olive mill wastewater after anaerobic digestion. A factorial experimental design was adopted to determine the statistical significance of each parameter tested, namely, initial chemical oxygen demand (COD), pH, treatment time and recirculation flow and possible interactions in three response variables: phenols, color and COD removals. Removal efficiencies of 90.8 ± 2.7%, 79.3 ± 1.9% and 50.3 ± 6.3% were obtained for total phenols (TPh), color and COD respectively. TPh and color were almost completely removed after 24 h of treatment, while the COD removal was partial. Because increasing the treatment time is economically unfeasible a recirculation to the anaerobic reactor should be considered. Regarding the most significant variables, the TPh removal efficiency is dependent of the initial COD concentration; the color removal efficiency decreased with increasing COD concentration and pH; and, the COD removal efficiency is directly linked with the treatment time. The interaction between the initial COD and treatment time affect negatively the response variables tested because of the inactivation of some active sites of the TiO₂ paper.

A photo-reactor with immobilized UV/TiO₂ was used for the post treatment of Olive Mill Wastewater, after anaerobic digestion. A factorial experimental design was used to assess possible interaction effects on chemical oxygen demand (COD), total phenols and colour removals, using four independent variables: initial COD concentration, pH, treatment time and contact time. The total phenols and colour were almost completely removed after 24 h of treatment (>90%), while COD was more difficult to remove (<50%). The reactor efficiency is highly dependent of the initial COD (negative effect) and treatment time (positive effect). The interaction effect between initial COD and treatment time must be considered.

We synthesized a series of cross-linked photoresponsive polymeric particles with photolabile monomers and cross-linkers through miniemulsion polymerization. These particles are quite stable in dark, while light irradiation caused the breakage of particles and the efficient release of encapsulated contents up to 95% based on Nile red fluorescence. Photoswitches of particle systems were confirmed by fluorescence spectroscopy, SEM and colorimetry. Particle uptake and triggered release in RAW264.7 cells were confirmed by fluorescein diacetate loaded particles.

Crosslinked photoresponsive polymeric nanoparticles encapsulated with target substances were synthesized with cross-linkers and photolabile monomers through miniemulsion polymerization. These nanoparticles are quite stable in dark, while light irradiation triggered the burst release of trapped targets in both aqueous solutions and cells.

The photochemical degradation of 2-(1-naphthyl) acetamide (NAD) in aqueous solution using simulated sunlight excitation as well as UV light within the 254–300 nm range was investigated to obtain an insight into the transformation mechanism that could occur under environmental conditions. Several photoproducts were identified using HPLC/MS/MS techniques. The degradation quantum yield was found to be independent of the excitation wavelength, but showed a dependence of oxygen concentration. This increased by a factor of approximately 3 from aerated to oxygen-free solutions. There is a clear involvement of both triplet and singlet excited states in NAD photoreactivity. The participation of singlet oxygen as a significant route in NAD degradation was ruled out by comparison with the behavior using Rose Bengal as a photosensitizer. A mechanistic pathway implying hydroxylation process through NAD radical cation species as well as an oxidation reaction by molecular oxygen is proposed. The photochemical behavior of NAD appears to mainly involve the aromatic moieties without any participation of the amide side chain. Toxicity tests clearly show that the generated primary photoproducts are responsible for a significant increase in the toxicity. However, upon prolonged irradiation this toxicity tends to decrease.

The degradation of the plant growth regulator 2-(1-Naphthyl) acetamide (NAD) in aqueous solution using simulated sunlight excitation as well as UV light within the 254–300 nm range is reported. The kinetics of NAD degradation is highly influenced by oxygen concentration and independent on excitation wavelength. The involvement of NAD singlet and triplet excited states on the NAD photochemical degradation was demonstrated. The primary photoproducts were identified by HPLC/MS/MS and these are clearly responsible for a significant increase in the toxicity. A degradation mechanism involving mainly hydroxylation and oxidation reactions is proposed.

Ground-state vibrational analyses of firefly luciferin and its conjugate acids and bases are performed. The Gibbs free energies obtained from these analyses are used to estimate pK_a values for phenolic hydroxy and carboxy groups and the N–H⁺ bond in the N-protonated thiazoline or benzothiazole ring of firefly luciferin. The theoretical pK_a values are corrected using the experimental values. The concentrations of these chemical species in solutions with different pH values are estimated from their corrected pK_a values, and the pH dependence of their relative absorption intensities is elucidated. With the results obtained we assign the experimental spectra unequivocally. Especially, the small peak near 400 nm at pH 1–2 in experimental absorption spectra is clarified to be due to the excitation of carboxylate anion with N-protonated thiazoline ring of firefly luciferin. Our results show that the pK_a values of chemical species, which are contained in the aqueous solutions, are effective to assign experimental absorption spectra.

With the help of theoretical pK_a values in the ground state the experimental absorption spectra of firefly luciferin and its conjugate acids and bases in solution with various pH values were successfully assigned.

Grape berry development and ripening depends mainly on imported photosynthates from leaves, however, fruit photosynthesis may also contribute to the carbon economy of the fruit. In this study pulse amplitude modulated chlorophyll fluorescence imaging (imaging-PAM) was used to assess photosynthetic properties of tissues of green grape berries. In particular, the effect of the saturation pulse (SP) intensity was investigated. A clear tissue-specific distribution pattern of photosynthetic competence was observed. The exocarp revealed the highest photosynthetic capacity and the lowest susceptibility to photoinhibition, and the mesocarp exhibited very low fluorescence signals and photochemical competence. Remarkably, the seed outer integument revealed a photosynthetic ability similar to that of the exocarp. At a SP intensity of 5000 μmol m⁻² s⁻¹ several photochemical parameters were decreased, including maximum fluorescence in dark-adapted (F_m) and light-adapted (F'_m) samples and effective quantum yield of PSII (Φ_II), but the inner tissues were susceptible to a SP intensity as low as 3200 μmol m⁻² s⁻¹ under light-adapted conditions, indicating a photoinhibitory interaction between SP and actinic light intensities and repetitive exposure to SP. These results open the way to further studies concerning the involvement of tissue-specific photosynthesis in the highly compartmentalized production and accumulation of organic compounds during grape berry development.

Imaging-PAM proved to be a sensitive technique for the study of in vivo photosynthesis in grape berry, allowing detecting tissue-specific differences. It was also found that in photosynthetic heterogeneous systems like grape berry sections, with tissues adapted to different light intensities, the optimization of the saturation pulse intensity is crucial for the accurate determination of photochemical parameters, as photoinhibition may occur at moderate light intensities and in a tissue-dependent manner. Being a fleshy fruit, with a large watery pericarp limiting light and gas diffusion, it was interesting to find a photosynthetically active seed outer integument, suggesting a key role for seed photosynthesis.

Synthetic bacteriochlorins enable systematic tailoring of substituents about the bacteriochlorin chromophore and thereby provide insights concerning the native bacteriochlorophylls of bacterial photosynthesis. Nine free-base bacteriochlorins (eight prepared previously and one prepared here) have been examined that bear diverse substituents at the 13- or 3,13-positions. The substituents include chalcone (3-phenylprop-2-en-1-onyl) derivatives with groups attached to the phenyl moiety, a “reverse chalcone” (3-phenyl-3-oxo-1-enyl), and extended chalcones (5-phenylpenta-2,4-dien-1-onyl, retinylidenonyl). The spectral and photophysical properties (τ_s, Φ_f, Φ_ic, Φ_isc, τ_T, k_f, k_ic, k_isc) of the bacteriochlorins have been characterized. The bacteriochlorins absorb strongly in the 780–800 nm region and have fluorescence quantum yields (Φ_f) in the range 0.05–0.11 in toluene and dimethylsulfoxide. Light-induced electron promotions between orbitals with predominantly substituent or macrocycle character or both may give rise to some net macrocycle ↔ substituent charge-transfer character in the lowest and higher singlet excited states as indicated by density functional theory (DFT) and time-dependent DFT calculations. Such calculations indicated significant participation of molecular orbitals beyond those (HOMO − 1 to LUMO + 1) in the Gouterman four-orbital model. Taken together, the studies provide insight into the fundamental properties of bacteriochlorins and illustrate designs for tuning the spectral and photophysical features of these near-infrared-absorbing tetrapyrrole chromophores.

The photophysical properties (Φ_s, Φ_f, Φ_ic, Φ_isc, τ_T, k_f, k_ic, k_isc) of nine free-base bacteriochlorins bearing chalcone, extended chalcone or reverse chalcone substituents have been characterized and interpreted with the aid of molecular-orbital calculations. The bacteriochlorins absorb strongly in the 780–800 nm region and provide models for photosynthetic bacteriochlorophylls.

Photophysical, photostability, electrochemical and molecular-orbital characteristics are analyzed for a set of stable dicyanobacteriochlorins that are promising photosensitizers for photodynamic therapy (PDT). The bacteriochlorins are the parent compound (BC), dicyano derivative (NC)₂BC and corresponding zinc (NC)₂BC-Zn and palladium chelate (NC)₂BC-Pd. The order of PDT activity against HeLa human cancer cells in vitro is (NC)₂BC-Pd > (NC)₂BC > (NC)₂BC-Zn ≈ BC. The near-infrared absorption feature of each dicyanobacteriochlorin is bathochromically shifted 35–50 nm (748–763 nm) from that for BC (713 nm). Intersystem crossing to the PDT-active triplet excited state is essentially quantitative for (NC)₂BC-Pd. Phosphorescence from (NC)₂BC-Pd occurs at 1122 nm (1.1 eV). This value and the measured ground-state redox potentials fix the triplet excited-state redox properties, which underpin PDT activity via Type-1 (electron transfer) pathways. A perhaps counterintuitive (but readily explicable) result is that of the three dicyanobacteriochlorins, the photosensitizer with the shortest triplet lifetime (7 μs), (NC)₂BC-Pd has the highest activity. Photostabilities of the dicyanobacteriochlorins and other bacteriochlorins studied recently are investigated and discussed in terms of four phenomena: aggregation, reduction, oxidation and chemical reaction. Collectively, the results and analysis provide fundamental insights concerning the molecular design of PDT agents.

Photophysical, electrochemical, redox and photostability characteristics are presented for a set of stable dicyanobacteriochlorins. Analysis of the collective results together with those for other bacteriochlorins and several porphyrins provides fundamental insights into the molecular tuning of photosensitizers for enhanced photostability and photodynamic therapy potency.

There is evidence indicating that the cellular locus of PDT action by amphiphilic sensitizers are the cellular membranes. The photosensitization process causes oxidative damage to membrane components that can result in the cell's death. However, it was not yet established whether lipid oxidation can cause free passage of molecules through the membrane and, as a result, be the primary cause of the cell's death. In this work, we studied the effect of liposomes' lipid composition on the kinetics of the leakage of three fluorescent dyes, calcein, carboxyfluorescein and DTAF, which were trapped in the intraliposomal aqueous phase, after photosensitization with the photosensitizer deuteroporphyrin. We found that as the degree of fatty acid unsaturation increased, the photosensitized passage of these molecules through the lipid bilayer increased. We also found that the rate of leakage of these molecules was affected by their size and bulkiness as well as by their net electric charge. In liposomes that are composed of a lipid mixture similar to that of natural membranes, the observed passage of molecules through the membrane is slow. Thus, the photodynamic damage to lipids does not appear to be severe enough to be an immediate, primary cause of cell death in biological photosensitization.

We examined the permeation of large fluorescent molecules through the liposomal membrane as a result of photodynamic damage. Liposomes containing high concentration of self-quenched dye have almost no fluorescence. When the lipid bilayer is damaged, the dye is released to the outer phase, it is diluted and it becomes highly fluorescent. We found that as the degree of fatty acid unsaturation increased the photosensitized passage of these molecules through the bilayer increased.

Cell-penetrating peptides such as TAT or R9 labeled with small organic fluorophores can lyse endosomes upon light irradiation. The photoendosomolytic activity of these compounds can in turn be used to deliver proteins and nucleic acids to the cytosol of live cells with spatial and temporal control. In this report, we examine the mechanisms by which such fluorescent peptides exert a photolytic activity using red blood cells as a membrane model. We show that the peptides TAT and R9 labeled with tetramethylrhodamine photolyze red blood cells by promoting the formation of singlet oxygen in the vicinity of the cells' membranes. In addition, unlabeled TAT and R9 accelerate the photolytic activity of the membrane-bound photosensitizer Rose bengal in trans, suggesting that the cell-penetrating peptides participate in the destabilization of photo-oxidized membranes. Peptides and singlet oxygen generators therefore act in synergy to destroy membranes upon irradiation.

Cell-penetrating peptides (CPPs) such as TAT or R9 labeled with small organic fluorophores can lyse endosomes upon light irradiation, thereby providing a means to deliver macromolecules to the cytosol of live cells with spatial and temporal control. We show that TAT and R9 labeled with tetramethylrhodamine can photolyze red blood cells by formation of singlet oxygen in the vicinity of the cells' membrane. Unlabeled TAT and R9 accelerate the photodamage caused by the membrane-bound photosensitizer Rose bengal in trans, suggesting that CPPs participate in the destabilization of photo-oxidized membranes. Peptides and singlet oxygen generators therefore act in synergy to destroy membranes upon irradiation.

Early work identified three compounds, namely the c,s cyclobutane dimer, the so-called (6-4) photoproduct (5-hydroxy-6-4′-(5-methylpyrimidin-2′-one)-5,6-dihydrothymine) and a trimer hydrate, as products formed upon UV irradiation of thymine in frozen aqueous solution. More recent work has shown that an (α-4) product, namely α-4′-(5′-methylpyrimidine-2′-one)-thymine, is a likely product formed under these reaction conditions. During a thorough reinvestigation of the photochemistry of Thy in ice at −78.5°C, we found that a variety of other products could be detected. In addition to the c,s dimer, the other three known cyclobutane dimers, namely the c,a, t,s and t,a forms, are produced, although in considerably smaller amounts. The so-called “spore product” of thymine (5,6-dihydro-5-(α-thyminyl)thymine) is likewise formed. Two other dimers have been identified as minor products; one of these has been determined to be 5-(thymin-3-yl)-5,6-dihydrothymine and the other has been tentatively assigned to be a (5-4) adduct (6-hydroxy-5-4′-(5-methylpyrimidin-2′-one)-5,6-dihydrothymine). Compounds with the behavior expected of true trimeric compounds have been isolated via HPLC and characterized by mass spectrometry and photochemical behavior. One of these materials, putatively containing an oxetane ring, decomposes thermally to a secondary trimeric product that is then converted into the known trimer hydrate.

The photochemistry occurring when thymine is irradiated in ice has been restudied. Besides previously observed products (the c,s cyclobutane dimer, the so-called (6-4) adduct (5-hydroxy-6-4′-(5-methylpyrimidin-2′-one)-5,6-dihydrothymine), trimer hydrate and an α-4 product (α-4′-(5′-methylpyrimidine-2′-one)-thymine (IX)), a number of other products have been characterized. Two non-cyclobutane type dimeric minor products that have been identified are displayed in the graphic, namely (5-thymin-3-yl)-5,6-dihydrothymine (VIII) and the “spore product” (5,6-dihydro-5-(α-thyminyl)thymine) (X). Also identified were the other three cyclobutane dimers (the c,a, t,s and t,a isomers), a thymine trimer (along with its trimeric thermal decomposition product) and a compound tentatively identified as a (5-4) adduct.

The purpose of this study was to explore the possible link between metals and UV-B-induced damage in bacteria. The effect of growth in the presence of enhanced concentrations of different transition metals (Co, Cu, Fe, Mn and Zn) on the UV-B sensitivity of a set of bacterial isolates was explored in terms of survival, activity and oxidative stress biomarkers (ROS generation, damage to DNA, lipid and proteins and activity of antioxidant enzymes). Metal amendment, particularly Fe, Cu and Mn, enhanced bacterial inactivation during irradiation by up to 35.8%. Amendment with Fe increased ROS generation during irradiation by 1.2–13.3%, DNA damage by 10.8–37.4% and lipid oxidative damage by 9.6–68.7%. Lipid damage during irradiation also increased after incubation with Cu and Co by up to 66.8% and 56.5% respectively. Mn amendment decreased protein carbonylation during irradiation by up to 44.2%. These results suggest a role of Fe, Co, Cu and Mn in UV-B-induced bacterial inactivation and the importance of metal homeostasis to limit the detrimental effects of ROS generated during irradiation.

Metals, most notably iron, play a crucial role in UV-B-induced oxidative stress. UV-B enhances the production of ROS in the cell. ROS, particularly the superoxide radical, can oxidize the Fe–S clusters of proteins. The process releases free iron ions [Fe²⁺] and hydrogen peroxide that can participate in Fenton and Haber–Weiss reactions that generate the highly toxic hydroxyl (OH^●) radical, which can cause oxidative damage to lipids, DNA and other proteins.

The UVA is currently thought to be carcinogenic because, similar to UVB, it induces the formation of cyclobutane pyrimidine dimers (CPDs). Various drugs have been reported to cause photosensitive drug eruptions as an adverse effect. Although the precise mechanism of photosensitive drug eruption remains to be elucidated, it is generally accepted that free radicals and other reactive molecules generated via UV-irradiated drugs play important roles in the pathogenesis of photosensitive drug eruptions. The waveband of concern for photo-reactive drugs is UVA-visible light, but some extend into the UVB region. We tested whether photosensitive drugs could enhance CPD formation after UVA exposure by using isolated DNA in the presence of several reported photosensitive drugs using high-performance liquid chromatography. We found that the diuretic agent hydrochlorothiazide (HCT) significantly enhanced the production of TT dimers over a wide range of UVA. Furthermore, we investigated whether UVA plus HCT could enhance CPD production in xeroderma pigmentosum model mice defective in nucleotide excision repair. Immunofluorescence studies showed that CPD formation in the skin significantly increased after 365 nm narrow-band UVA irradiation in the presence of HCT, compared with that in wild-type mice. HCT could be used with caution because of its enhancement of UVA-induced DNA damage.

Various drugs have been reported to cause photosensitive drug eruptions as an adverse effect. We tested whether photosensitive drugs could enhance CPD formation after UVA exposure by using isolated DNA in the presence of several photosensitive drugs using high-performance liquid chromatography. The diuretic agent hydrochlorothiazide (HCT) significantly enhanced the production of thymine dimers over a wide range of UVA. We also investigated whether UVA plus HCT could enhance CPD production in mice skin. Immunofluorescence studies showed that CPD formation in the dermal skin significantly increased after 365 nm narrow-band UVA irradiation in the presence of HCT.

This study aimed to analyze the phototoxic mechanism and photostability of quinine in human skin cell line A375 under ambient intensities of UVA (320–400 nm). Photosensitized quinine produced a photoproduct 6-methoxy-quinoline-4-ylmethyl-oxonium identified through LC-MS/MS. Generation of ¹O₂, O₂^•−, and ^•OH was measured and further substantiated through their respective quenchers. Photosensitized Quinine (Q) caused degradation of 2-deoxyguanosine, the most sensitive nucleotide to UV radiation. The intracellular ROS was increased in a concentration-dependent manner. Significant reduction in metabolic status measured in terms of cell viability (54%) at 25 μg mL⁻¹ was observed through MTT assay. Results of MTT assay accord NRU assay. Single strand DNA breaks and apoptosis were increased significantly (P < 0.01) as observed through comet assay and EB/AO double staining. Photosensitized quinine caused cells to arrest in G₂ phase of cell cycle and induced apoptosis (5.08%) as revealed through FACS. Real-Time PCR showed upregulation of p21 (4.56 folds) and p53 (2.811 folds) genes expression. Thus, our study suggests that generation of reactive oxygen species by quinine under ambient intensity of UVA may result into deleterious phototoxic effects among human population.

UVA-photosensitized quinine produced photoproduct, generated ROS and caused DNA damage either directly or indirectly, which in turn arrest cell cycle and induce apoptosis and finally cell death in A375 cells.

People can get oral cancers from UV (290–400 nm) exposures. Besides high outdoor UV exposures, high indoor UV exposures to oral tissues can occur when consumers use UV-emitting tanning devices to either tan or whiten their teeth. We compared the carcinogenic risks of skin to oral tissue cells after UVB (290–320 nm) exposures using commercially available 3D-engineered models for human skin (EpiDerm™), gingival (EpiGing™) and oral (EpiOral™) tissues. To compare the relative carcinogenic risks, we investigated the release of cytokines, initial DNA damage in the form of cyclobutane pyrimidine dimers (CPDs), repair of CPDs and apoptotic cell numbers. We measured cytokine release using cytometric beads with flow cytometry and previously developed a fluorescent immunohistochemical assay to quantify simultaneously CPD repair rates and apoptotic cell numbers. We found that interleukin-8 (IL-8) release and the initial CPDs are significantly higher, whereas the CPD repair rates and apoptotic cell numbers are significantly lower for oral compared with skin tissue cells. Thus, the increased release of the inflammatory cytokine IL-8 along with inefficient CPD repair and decreased death rates for oral compared with skin tissue cells suggests that mutations are accumulating in the surviving population of oral cells increasing people's risks for getting oral cancers.

Because people can get oral cancers from UV radiation, we compared the carcinogenic risks of skin with oral tissue cells after UVB (290–320 nm) exposures using commercially available 3D-engineered models for human skin, gingival and oral tissues. We compared the relative carcinogenic risks by measuring cytokine release, repair rates of cyclobutane pyrimidine dimers (CPD red; all DNA blue) and apoptotic cell numbers (green). We find that IL-8 is significantly higher whereas CPD repair rates and apoptotic cell numbers are significantly lower for oral compared with skin tissue cells. Thus, oral cells can accumulate more mutations per UVB dose than skin cells.

Immobilization of photosensitizers in polymers opens prospects for their continuous and reusable application. Methylene blue (MB) and Rose Bengal were immobilized in polystyrene by mixing solutions of the photosensitizers in chloroform with a polymer solution, followed by air evaporation of the solvent. This procedure yielded 15–140 μm polymer films with a porous surface structure. The method chosen for immobilization ensured 99% enclosure of the photosensitizer in the polymer. The antimicrobial activity of the immobilized photosensitizers was tested against Gram-positive and Gram-negative bacteria. It was found that both immobilized photosensitizers exhibited high antimicrobial properties, and caused by a 1.5–3 log₁₀ reduction in the bacterial concentrations to their total eradication. The bactericidal effect of the immobilized photosensitizers depended on the cell concentration and on the illumination conditions. Scanning electron microscopy was used to prove that immobilized photosensitizers excited by white light caused irreversible damage to microbial cells. Photosensitizers immobilized on a solid phase can be applied for continuous disinfection of wastewater bacteria.

Immobilization of photosensitizers in polymers opens prospects for their continuous and reusable application. Methylene blue (MB) and Rose Bengal were immobilized in polystyrene by mixing solutions of the photosensitizers in chloroform with a polymer solution, followed by air evaporation of the solvent. This procedure yielded 15–140 μm polymer films with a porous surface structure. The method chosen for immobilization ensured 99% enclosure of the photosensitizer in the polymer. The antimicrobial activity of the immobilized photosensitizers was proven against Gram-positive and Gram-negative bacteria (Figure). Photosensitizers immobilized on a solid phase can be applied for continuous disinfection of bacteria in wastewater.

We previously reported that photodynamic therapy (PDT) using intra-articular methylene blue (MB) could be used to treat arthritis in mice caused by bioluminescent methicillin-resistant Staphylococcus aureus (MRSA) either in a therapeutic or in a preventative mode. PDT accumulated neutrophils into the mouse knee via activation of chemoattractants such as inflammatory cytokines or chemokines. In this study, we asked whether PDT combined with antibiotics used for MRSA could provide added benefit in controlling the infection. We compared MB-PDT alone, systemic administration of either linezolid (LZD) alone or vancomycin (VCM) alone or the combination of PDT with either LZD or VCM. Real-time noninvasive imaging was used to serially follow the progress of the infection. PDT alone was the most effective, whereas LZD alone was ineffective and VCM alone showed some benefit. Surprisingly the addition of LZD or VCM reduced the therapeutic effect of PDT alone (P < 0.05). Considering that PDT in this mouse model stimulates neutrophils to be antibacterial rather than actively killing the bacteria, we propose that LZD and VCM might inhibit the activation of inflammatory cytokines without eradicating the bacteria, and thereby reduce the therapeutic effect of PDT.

Mouse bacterial arthritis caused by bioluminescent MRSA can be treated by injection of methylene blue into the knee joint and illumination with red light. When the PDT was combined with anti-MRSA antibiotics the effectiveness was less, rather than more as expected. This may be due to the action of antibiotics in reducing the inflammatory response stimulated by PDT that causes an influx of neutrophils that actually kill the bacteria.

We examined the effect of the oxygenation level on efficacy of two photosensitizing agents, both of which target lysosomes for photodamage, but via different photochemical pathways. Upon irradiation, the chlorin termed NPe6 forms singlet oxygen in high yield while the bacteriopheophorbide WST11 forms only oxygen radicals (in an aqueous environment). Photokilling efficacy by WST11 in cell culture was impaired when the atmospheric oxygen concentration was reduced from 20% to 1%, while photokilling by NPe6 was unaffected. Studies in a cell-free system revealed that the rates of photobleaching of these agents, as a function of the oxygenation level, were correlated with results described above. Moreover, the rate of formation of oxygen radicals by either agent was more sensitive to the level of oxygenation than was singlet oxygen formation by NPe6. These data indicate that the photochemical process that leads to oxygen radical formation is more dependent on the oxygenation level than is the pathway leading to formation of singlet oxygen.

Irradiation of photosensitizing agents creates reactive oxygen species (ROS), leading to phototoxic effects and photobleaching phenomena. In this report, we examine the efficacy of different ROS as a function of the oxygenation level.

A novel pyropheophorbide-a (PPa) derivative, Ac-sPPp, was developed in our lab for targeted photodynamic therapy (PDT) and combination therapies. Its versatile peptide moiety, high water-solubility, amphiphilicity, and micellar aggregation allow efficient coupling to targeting moieties and convenient mixing with other therapeutics. Photosensitizer immunoconjugate (PIC) targeted PDT, using Ac-sPPp conjugated to therapeutic anti-epidermal growth factor receptor (EGFR) antibody cetuximab, and PDT + chemotherapy combination treatment, using Ac-sPPp mixed with stealth liposomal doxorubicin (Doxil), were investigated as promising strategies for potentiating PDT and improving target specificity. Passively targeted PDT with Ac-sPPp only or surfactant-solubilized PPa was also investigated for comparison. The A-431 human vulvar squamous cell carcinoma, xenografted in nude mice, was chosen as a tumor model because of its high EGFR expression and sensitivity to liposomal doxorubicin in vitro. Fluorescence imaging and PDT experiments showed that Ac-sPPp formulations circulated far longer and provided superior tumor contrast and superior tumor control compared to PPa. Strong PDT vascular effects were observed by laser Doppler imaging regardless of whether Ac-sPPp was passively or actively targeted. Passively targeted Ac-sPPp PDT gave equivalent or better tumor control than PIC-targeted PDT or PDT + Doxil combination therapy, and when treatments were repeated, it also yielded the highest cure rate.

To potentiate and improve the targeting of photodynamic therapy (PDT), an amphiphilic polyethylene glycolated pyropheophorbide-a (PPa) derivative, Ac-sPPp, was investigated as a novel water-soluble photosensitizer that could be easily coupled to cancer-targeting molecules or combined with other therapeutics. In a recurrent A-431 tumor xenograft model, passively and actively targeted Ac-sPPp formulations exerted strong vascular effects and provided superior fluorescence contrast and tumor control compared to PPa, but efforts to improve targeting and potency by formulating Ac-sPPp as an anti-erbB immunoconjugate or combining it with Doxil chemotherapy were less important to achieving tumor cures than simply repeating PDT.

Sparing sensitive healthy tissue from chemotherapy exposure is a critical challenge in the treatment of cancer. The work described here demonstrates the localized in vivo photoactivation of a new chemotherapy prodrug of doxorubicin (DOX). The DOX prodrug (DOX-PCB) was 200 times less toxic than DOX and was designed to release pure DOX when exposed to 365 nm light. This wavelength was chosen because it had good tissue penetration through a 1 cm diameter tumor, but had very low skin penetration, due to melanin absorption, preventing uncontrolled activation from outside sources. The light was delivered specifically to the tumor tissue using a specialized fiber-optic LED system. Pharmacokinetic studies showed that DOX-PCB had an α circulation half-life of 10 min which was comparable to that of DOX at 20 min. DOX-PCB demonstrated resistance to metabolic cleavage ensuring that exposure to 365 nm light was the main mode of in vivo activation. Tissue extractions from tumors exposed to 365 nm light in vivo showed the presence of DOX-PCB as well as activated DOX. The exposed tumors had six times more DOX concentration than nearby unexposed control tumors. This in vivo proof of concept demonstrates the first preferential activation of a photocleavable prodrug in deep tumor tissue.

Reducing the side effects of chemotherapy treatment involves reducing the amount of active agent that reaches the healthy tissue while simultaneously increasing the amount within the tumor. This study looks to achieve these goals by using a systemically distributed photocleavable prodrug of doxorubicin and activating it specifically in tumor tissue with the use of a fiber-optic/LED system that delivers the activating wavelength of light to the center of the tumor. The doxorubicin prodrug was 200 times less toxic than the pure doxorubicin that was released from it. Here, we show that a six-fold increase in pure doxorubicin was found in the light-exposed tumor versus the neighboring unexposed control tumor.

The tight skin mouse (Tsk^−/+) is a model of scleroderma characterized by impaired vasoreactivity, increased oxidative stress, attenuated angiogenic response to VEGF and production of the angiogenesis inhibitor angiostatin. Low-level light therapy (LLLT) stimulates angiogenesis in myocardial infarction and chemotherapy-induced mucositis. We hypothesize that repetitive LLLT restores vessel growth in the ischemic hindlimb of Tsk^−/+ mice by attenuating angiostatin and enhancing angiomotin effects in vivo. C57Bl/6J and Tsk^−/+ mice underwent ligation of the femoral artery. Relative blood flow to the foot was measured using a laser Doppler imager. Tsk^−/+ mice received LLLT (670 nm, 50 mW cm⁻², 30 J cm⁻²) for 10 min per day for 14 days. Vascular density was determined using lycopersicom lectin staining. Immunofluorescent labeling, Western blot analysis and immunoprecipitation were used to determine angiostatin and angiomotin expression. Recovery of blood flow to the ischemic limb was reduced in Tsk^−/+ compared with C57Bl/6 mice 2 weeks after surgery. LLLT treatment of Tsk^−/+ mice restored blood flow to levels observed in C57Bl/6 mice. Vascular density was decreased, angiostatin expression was enhanced and angiomotin depressed in the ischemic hindlimb of Tsk^−/+ mice. LLLT treatment reversed these abnormalities. LLLT stimulates angiogenesis by increasing angiomotin and decreasing angiostatin expression in the ischemic hindlimb of Tsk^−/+ mice.

Collateral growth is impaired in the ischemic hindlimb in a murine model of scleroderma. Impaired collateral growth is characterized by increased levels of the angiogenesis inhibitor angiostatin and decreased levels of the pro-angiogenic protein angiomotin. Low-level light therapy (LLLT) induced topical nitric oxide release which restored collateral growth by reducing the expression levels of the angiostatin by increasing topical nitric oxide levels and the expression of angiomotin. Low-level light therapy stimulates angiogenesis by increasing angiomotin and decreasing angiostatin expression in the ischemic hindlimb in the murine scleroderma.

Our aim was to examine the association between ethnicity, phenotype, sun behavior and other characteristics, and constitutive and relative facultative skin pigmentation. A total of 191 participants were recruited, with a mean age of 7.6 years (SD 3.4), during 2009–2011 from Maternal and Child Health Centres (MCHC) and schools in Melbourne, Australia. Parental questionnaire data were obtained on sun behavior and examination consisted of noting the child's natural skin, hair and eye color, ethnicity, nevi count and spectrophotometric melanin density (MD). Constitutive skin pigmentation was estimated from buttock MD. Relative facultative skin pigmentation was estimated by hand compared with buttock absorption. Ethnicity, hair color and skin color were associated with constitutive and facultative skin pigmentation on univariate analysis. Higher ambient ultraviolet radiation (UVR) in the past month, greater freckling, greater nevi and increased sun exposure over the past year were related to darker facultative skin pigmentation. Sun exposure over the life course was not. The two skin charts accounted for 39.7% and 21.4% of buttock MD, respectively. Relative facultative skin pigmentation is associated with recent UVR levels, not life-course sun exposure. Relative facultative skin pigmentation may not be a useful measure of sun exposure over the early life course. Skin color charts can be used to assess constitutive skin pigmentation if spectrophotometry is not available.

Constitutive skin pigmentation is the natural skin color, and facultative skin pigmentation (tanning) is associated with exposure to the sun and is often defined relative to constitutive skin pigmentation at an unexposed skin site. The figure shows that there was no variation for constitutive skin pigmentation by month of interview. For relative facultative skin pigmentation, there was greater variation, with less tanning midyear (winter) and most tanning during the summer months.

Differences between global radiation UVER (erythemal ultraviolet solar radiation) received under full sun and diffuse radiation received under the shadow of two types of tree are analyzed to check the importance of these components on human exposure to UV radiation. Blue Line spores dosimeters of VioSpor were used for measurement of erythemal dose of UV radiation (able to produce erythema in human skin.) The response profile of these devices is extremely similar to human skin, thus they are suitable to determine and predict the interactions between UV erythema and human skin. Measurements were obtained in relatively clear days from February to December 2009 between 9:30 and 15:30 h. Three dosimeters were placed on a horizontal surface: one in full sun and the other two under the shadow of each tree. Values of UVER in both cases, in full sun and under the shadow of pine and Sauce, were obtained. In addition, the comparison was made between values of dose received in each case and the exposure limits recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). Finally, average daily irradiance received under the shadow of each tree in comparison with those received in full sun, was also analyzed using two PMA2100 radiometers situated on a horizontal surface.

Differences between global radiation UVER (erythemal ultraviolet solar radiation) received under full sun and diffuse radiation received under the shadow of two types of tree are analyzed in order to check the importance of these components on human exposure to UV radiation. Measurements were obtained in relatively clear days from February to December 2009. Values of UVER in full sun and under the shadow of Pine and Sauce, were obtained. Finally, average daily irradiance received under the shadow of each tree in comparison with those received in full sun, was also analyzed.

Ultraviolet (UV) reflection in the urban constructed environment is not well understood for topical issues such as measuring and modeling the received UV exposure due to that UV reflection for outdoor workers. Both predominantly specular and diffuse reflecting surface types have been identified and investigated for the erythemal UV reflection ratio variation due to solar zenith angle and orientation. This paper presents relationships between erythemal UV reflection ratios measured for non-horizontal and horizontal surfaces, with predominantly specular surface types indicating stronger relationships with solar zenith angles than diffuse reflecting surfaces types. Erythemal UV exposures caused by the same reflecting surface types at three inclinations are also investigated. Non-horizontal surfaces can increase erythemal UV exposures compared to erythemal UV exposures received from the same horizontal surface by factors of 1.07–1.46 for specific body sites and by 1.01–1.70 for averages of group body sites for zinc aluminium coated steel sheeting.

Ultraviolet radiation reflective characteristics in the constructed environment for horizontal and non-horizontal surfaces are characterised for zinc aluminium coated trapezoidal shaped steel sheeting and pale green paint coated trapezoidal steel sheeting for solar zenith angle and season. The importance of this characterisation is due to the presence of specular reflection due to the metal surfaces as opposed to diffuse reflection. In addition the influence of these surface types is investigated for their influence on personal UV exposure, comparing non-horizontal surface influence to horizontal surface influence.

Spatio-temporal patterns in sun exposure underlie variations in skin cancer incidence and vitamin D deficiency, indicate effectiveness of sun protection programs and provide insights into future health risks. From 558 adults across four regions of Australia (Brisbane (27°S), Newcastle (33°S), Geelong and the Western Districts of Victoria (37°S) and Tasmania (43°S)), we collected: self-report data on time-in-the-sun from age 6 years; natural skin color and ethnicity; silicone skin casts (for cumulative skin damage); and serum for vitamin D status. Ambient ultraviolet radiation (UVR) at the location of residence, with time-in-the-sun, was used to calculate a “UVR dose” for each year of life. Individuals maintained their ranking compared to their peers for time-in-the-sun in summer compared to winter and across ages (Spearman rho 0.24–0.84, all P < 0.001). Time-in-the-sun decreased with age in all birth cohorts, and over calendar time. Summer time-in-the-sun increased with increasing latitude (P < 0.001). Seasonal variation in vitamin D status had greater amplitude and vitamin D deficiency increased with increasing latitude. Temporal patterns are consistent with effectiveness of sun protection programs. Higher relative time-in-the-sun persists from childhood through adulthood. Lower summer time-in-the-sun in the warmest location may have implications for predictions of UVR-related health risks of climate change.

Daily time in the sun during leisure time (hours, average of summer and winter): variation over calendar time in different age cohorts (age is taken to be the beginning of the age cohort, for example, 1940s—start age considered to be 1940; time in the sun for the time period is taken as the median age, for example, aged 6–10 years, age taken as 8 years. Thus, for persons in the 1940s age cohort, the time in the sun for the period at which they were aged 6–10 years, is plotted as 1948).

The variation characteristics of Ultraviolet-B (UVB; 280–315 nm) radiation over Beijing were explored using measured data that were collected in Beijing from November 2010 to October 2011. Seasonal variations in UVB radiation and influence of ozone and clearness index on the ratio of UVB to broadband solar radiation (G) were investigated. The annual value of UVB radiation in Beijing is 6.37 MJ m⁻², and monthly average value ranges from 4.96 to 28.37 kJ m⁻² d⁻¹. The maximum daily total UVB radiation ranges from 6.55 kJ m⁻² d⁻¹ in November to 54.22 kJ m⁻² d⁻¹ in July. The monthly minimum of daily total UVB radiation varies from 0.5 kJ m⁻² d⁻¹ in February to 11.52 kJ m⁻² d⁻¹ in July. The monthly average of the ratio of UVB radiation to G ranges from 0.007 to 0.017%, with an annual average value of 0.012%. The variation in slant ozone column causes annual cycle of the ratio UVB radiation to G, with maximum value in summer. In addition, clouds have a greater effect on G than UVB radiation. Thus, the ratio increases by more than 17% when the atmospheric conditions change from clear to cloudy.

There is an anticorrelation between UVB radiation and the concentration of fine aerosol (PM2.5) and this indicate that PM2.5 has great influence on the amount of UVB radiation that received at earth's surface. However, the highest value of UVB radiation appears at June other than the lowest concentration of PM2.5 at January. The variation in solar altitude has caused this difference.

Although allergic rhinitis is not life threatening, it significantly influences the quality of a patient's life. This study is intended to evaluate the safety and efficacy of phototherapy with low-level energy of a 650 nm laser irradiation system in perennial allergic rhinitis patients. This clinical trial was an open-label, single-center study with 42 perennial allergic rhinitis subjects. Following laser irradiation in the nasal cavity with a laser irradiation system, the efficacy at weeks 1 through 4 was determined. The symptoms were scored with four parameters (nasal obstruction, rhinorrhea, sneezing and itching) before and after illumination of the laser, and the total score was recorded. A survey of Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ) was conducted by patients before and after treatment. Following treatment, significant improvement in the clinical symptoms of nasal obstruction (P < 0.001), rhinorrhea (P = 0.005), sneezing (P = 0.001) and itching (P = 0.003) was reported by 68% of perennial allergic rhinitis patients. The overall RQLQ scores significantly improved by 45% from the baseline with the treatment after 4 weeks. These results indicate that phototherapy is an effective modality for treating perennial allergic rhinitis and is another option in the steroid-free management of immune-mediated mucosal diseases.

This study is intended to evaluate the safety and efficacy of phototherapy with low-level energy of a 650 nm laser irradiation system in perennial allergic rhinitis patients. Following laser irradiation in the nasal cavity with a laser irradiation system, the efficacy at weeks 1 through 4 was determined. The symptoms were scored with four parameters (nasal obstruction, rhinorrhea, sneezing and itching) before and after illumination of the laser. The overall RQLQ scores significantly improved by 45% from the baseline with the treatment after 4 weeks. These results indicate that phototherapy is an effective modality for treating perennial allergic rhinitis.

The photoprotective potential of fungus pigments was investigated by irradiating conidiospores of three Aspergillus niger strains possessing the same genetic background, but differing in their degree of pigmentation with pulsed light (PL) and monochromatic (254 nm) UV-C radiation. Spores of A. niger MA93.1 and JHP1.1 presenting, respectively, a fawn and a white pigmentation were more sensitive to PL and continuous UV-C radiation than the wild-type A. niger strain N402 possessing a dark pigment. Both spores of the dark A. niger N402 and the fawn-color mutant were equally resistant to moist heat at 56°C while spores of the white-color mutant were highly sensitive. These results indicate that melanin protects pigmented spores of A. niger from PL.

Spores of Aspergillus niger N402 (wild type) are black. Mutant strains of this exhibit different pigmentation. Spores of wild-type strain are much less sensitive to pulsed light or continuous UV-C than fawn or white spores of the mutants. This is likely due to the differences in melanin content.