Photochemistry and Photobiology

Cover image for Vol. 92 Issue 1

Edited By: Jean Cadet

Impact Factor: 2.266

ISI Journal Citation Reports © Ranking: 2014: 44/73 (Biophysics); 184/290 (Biochemistry & Molecular Biology)

Online ISSN: 1751-1097

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  • RESEARCH ARTICLE: Fluorinated Photodynamic Therapy Device Tips and their Resistance to Fouling for In Vivo Sensitizer Release

    RESEARCH ARTICLE: Fluorinated Photodynamic Therapy Device Tips and their Resistance to Fouling for In Vivo Sensitizer Release

    We describe progress on a one-step photodynamic therapy (PDT) technique that is simple: device tip delivery of sensitizer, oxygen and light simultaneously. Control is essential for their delivery to target sites to generate singlet oxygen. One potential problem is the silica device tip may suffer from biomaterial fouling and the pace of sensitizer photorelease is slowed. Here, we have used biomaterial (e.g. proteins, cells, etc.) from SQ20B head and neck tumors and whole blood for an assessment of fouling of the silica tips by adsorption. It was shown that by exchanging the native silica tip for a fluorinated tip, a better nonstick property led to an increased sensitizer output by ~10%. The fluorinated tip gave a sigmoidal photorelease where singlet oxygen is stabilized to physical quenching, whereas the native silica tip with unprotected SiO–H groups gave a slower (pseudolinear) photorelease. A further benefit from fluorinated silica is that 15% less biomaterial adheres to its surface compared to native silica based on a bicinchoninic acid assay (BCA) and X-ray photoelectron spectroscopy (XPS) measurements. We discuss how the fluorination of the device tip increases biofouling resistance and can contribute to a new pointsource PDT tool.

  • INVITED REVIEW: UV-induced DNA Damage: The Role of Electronic Excited States

    INVITED REVIEW: UV‐induced DNA Damage: The Role of Electronic Excited States

    The knowledge of the fundamental processes induced by the direct absorption of UV radiation by DNA allows extrapolating conclusions drawn from in vitro studies to the in-vivo DNA photoreactivity. In this respect, the characterization of the DNA electronic excited states plays a key role. For a long time, the mechanisms of DNA lesion formation were discussed in terms of generic “singlet” and “triplet” excited state reactivity. However, since the beginning of the 21st century, both experimental and theoretical studies revealed the existence of “collective” excited states, i.e. excited states delocalized over at least two bases. Two limiting cases are distinguished: Frenkel excitons (delocalized ππ* states) and charge-transfer states in which positive and negative charges are located on different bases. The importance of collective excited states in photon absorption (in particular in the UVA spectral domain), the redistribution of the excitation energy within DNA, and the formation of dimeric pyrimidine photoproducts is discussed. The dependence of the behavior of the collective excited states on conformational motions of the nucleic acids is highlighted.

  • RESEARCH ARTICLE: Photodynamic Diagnosis Using 5-Aminolevulinic Acid in 41 Biopsies for Primary Central Nervous System Lymphoma

    RESEARCH ARTICLE: Photodynamic Diagnosis Using 5‐Aminolevulinic Acid in 41 Biopsies for Primary Central Nervous System Lymphoma

    We evaluated the feasibility of 5-aminolevulinic acid (5-ALA)-mediated photodynamic diagnosis (PDD) in the biopsy for primary central nervous system lymphoma (PCNSL). 5-ALA (20 mg kg−1) was administered orally 4 hours preoperatively. Forty-one biopsies obtained under PDD in 47 consecutive biopsies (46 patients) that were finally pathologically diagnosed as PCNSL were evaluated. Positive fluorescence was observed in 34 of those 41 biopsies (82.9%). An intraoperative pathological diagnosis (IOD) of suspected PCNSL was made in 21 of the biopsies with positive fluorescence (61.8%). However, the eight IODs in the remaining 13 biopsies (23.5%) were not correct (atypical cell, 4; high-grade glioma, 1; gliosis, 1; unremarkable, 2). In those 8 biopsies, PCNSL was confirmed by the final pathological diagnosis. There was no difference in the mean Mib-1 labeling index between the biopsies with positive fluorescence (86.5%) and those without positive fluorescence (90.0%). IOD was not performed in 6 biopsies; however, 5 of those biopsies (83.3%) showed positive fluorescence and were finally pathologically diagnosed as PCNSL. Use of PDD in biopsies for patients with suspected PCNSL is a reliable way of obtaining specimens of adequate quality for the final pathological diagnosis and may lead to improved diagnostic yield in the biopsy of PCNSL.

  • RESEARCH ARTICLE: Photochemistry and Photobiology of the Spore Photoproduct: A 50-Year Journe

    RESEARCH ARTICLE: Photochemistry and Photobiology of the Spore Photoproduct: A 50‐Year Journe

    Fifty years ago, a new thymine dimer was discovered as the dominant DNA photolesion in UV-irradiated bacterial spores [Donnellan, J. E. & Setlow R. B. (1965) Science, 149, 308–310], which was later named the spore photoproduct (SP). Formation of SP is due to the unique environment in the spore core that features low hydration levels favoring an A-DNA conformation, high levels of calcium dipicolinate that acts as a photosensitizer, and DNA saturation with small, acid-soluble proteins that alters DNA structure and reduces side reactions. In vitro studies reveal that any of these factors alone can promote SP formation; however, SP formation is usually accompanied by the production of other DNA photolesions. Therefore, the nearly exclusive SP formation in spores is due to the combined effects of these three factors. Spore photoproduct photoreaction is proved to occur via a unique H-atom transfer mechanism between the two involved thymine residues. Successful incorporation of SP into an oligonucleotide has been achieved via organic synthesis, which enables structural studies that reveal minor conformational changes in the SP-containing DNA. Here, we review the progress on SP photochemistry and photobiology in the past 50 years, which indicates a very rich SP photobiology that may exist beyond endospores.

  • RESEARCH ARTICLE Effect of LED Blue Light on Penicillium digitatum and Penicillium italicum Strains

    RESEARCH ARTICLE Effect of LED Blue Light on Penicillium digitatum and Penicillium italicum Strains

    Studies on the antimicrobial properties of light have considerably increased due in part to the development of resistance to actual control methods. This study investigates the potential of light-emitting diodes (LED) blue light for controlling Penicillium digitatum and Penicillium italicum. These fungi are the most devastating postharvest pathogens of citrus fruit and cause important losses due to contaminations and the development of resistant strains against fungicides. The effect of different periods and quantum fluxes, delaying light application on the growth and morphology of P. digitatum strains resistant and sensitive to fungicides, and P. italicum cultured at 20°C was examined. Results showed that blue light controls the growth of all strains and that its efficacy increases with the quantum flux. Spore germination was always avoided by exposing the cultures to high quantum flux (700 μmol m−2 s−1) for 18 h. Continuous light had an important impact on the fungus morphology and a fungicidal effect when applied at a lower quantum flux (120 μmol m−2 s−1) to a growing fungus. Sensitivity to light increased with mycelium age. Results show that blue light may be a tool for P. digitatum and P. italicum infection prevention during handling of citrus fruits.

  • INVITED REVIEW: How Does Photoreceptor UVR8 Perceive a UV-B Signal?

    INVITED REVIEW: How Does Photoreceptor UVR8 Perceive a UV-B Signal?

    UVR8 is the only known plant photoreceptor that mediates light responses to UV-B (280–315 nm) of the solar spectrum. UVR8 perceives a UV-B signal via light-induced dimer dissociation, which triggers a wide range of cellular responses involved in photomorphogenesis and photoprotection. Two recent crystal structures of Arabidopsis thaliana UVR8 (AtUVR8) have revealed unusual clustering of UV-B-absorbing Trp pigments at the dimer interface and provided a structural framework for further mechanistic investigation. This review summarizes recent advances in spectroscopic, computational and crystallographic studies on UVR8 that are directed toward full understanding of UV-B perception at the molecular level.

  • RESEARCH ARTICLE: Fluorinated Photodynamic Therapy Device Tips and their Resistance to Fouling for In Vivo Sensitizer Release
  • INVITED REVIEW: UV‐induced DNA Damage: The Role of Electronic Excited States
  • RESEARCH ARTICLE: Photodynamic Diagnosis Using 5‐Aminolevulinic Acid in 41 Biopsies for Primary Central Nervous System Lymphoma
  • RESEARCH ARTICLE: Photochemistry and Photobiology of the Spore Photoproduct: A 50‐Year Journe
  • RESEARCH ARTICLE Effect of LED Blue Light on Penicillium digitatum and Penicillium italicum Strains
  • INVITED REVIEW: How Does Photoreceptor UVR8 Perceive a UV-B Signal?

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Synthetic DNA hairpins possessing a Michler’s ketone linker at one end separated from a perylenediimide base surrogate by four base pairs were designed to investigate transport of charge between the two chromophores. Pulsed laser excitation of Michler’s ketone with 400 nm light results in formation of a charge transfer excited state which returns to the group state without undergoing electron transport to perylenediimide (upper pathway). Excitation of perylenediimide with 545 nm light results in injection of a positive charge which is transported via the base pairs to Michler’s ketone (lower pathway). For details see the paper “Electronic Interactions of Michler’s Ketone with DNA Bases in Synthetic Hairpins” by Almaz S. Jalilov et al. on pages 739-747 in this issue.
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