Photochemistry and Photobiology

Cover image for Vol. 92 Issue 3

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:The Involvement of Splicing Factor hnRNP A1 in UVB-induced Alternative Splicing of hdm2 (

    RESEARCH ARTICLE:The Involvement of Splicing Factor hnRNP A1 in UVB‐induced Alternative Splicing of hdm2 (

    Human homolog double minute 2 (hdm2), an oncoprotein, which binds to tumor suppressor p53 to facilitate its degradation, has been known to contribute to tumorigenesis. Its splicing variants are reported to be highly expressed in many cancers and can be induced by ultraviolet B light (UVB). However, the mechanisms of how UVB radiation induces hdm2 alternative splicing still remain unclear. In this study, we investigated the roles of two common splicing factors, heterogeneous nuclear ribonucleoproteins (hnRNP) A1 and serine/arginine-rich splicing factor 1 (SRSF1), in regulating UVB-induced hdm2 splicing. Our study indicated that while the expression of both hnRNP A1 and SRSF1 are induced, only hnRNP A1 is involved in hdm2 alternative splicing upon UVB irradiation. Overexpression of hnRNP A1 resulted in decrease of full-length hdm2 (hdm2-FL) and increase of hdm2B, one of hdm2 alternate-splicing forms; while down-regulated hnRNP A1 expression led to the decrease of the hdm2-FL and hdm2B in HaCaT cells. Protein-mRNA binding assay confirmed that UVB irradiation could increase the binding of hnRNP A1 to hdm2 pre-mRNA. In conclusion, we elucidated that UVB induces alternative splicing of hdm2 via increasing the expression and the binding of hnRNP A1 to hdm2 full-length mRNA.

  • RESEARCH ARTICLE:Stereoselective Self-Aggregation of 31-Epimerically Pure Amino Analogs of Zinc Bacteriochlorophyll-d in an Aqueous Micelle Solution

    RESEARCH ARTICLE:Stereoselective Self‐Aggregation of 31‐Epimerically Pure Amino Analogs of Zinc Bacteriochlorophyll‐d in an Aqueous Micelle Solution

    Zinc bacteriochlorophyll-d analogs possessing an amino group instead of the original hydroxy group at the C31 position were prepared by chemical modification of naturally occurring chlorophyll-a. The synthetic 31-epimers were successfully separated by reverse phase HPLC to give diastereomerically pure samples. The stereochemistry of the chiral C31-center in the separated amines was determined by NMR analysis of their diastereomeric amides as well as by their asymmetric synthesis from authentic stereoisomers. Both the epimers were monomeric in tetrahydrofuran to give sharp electronic absorption bands, while they self-aggregated to form chlorosomal oligomers with the redshifted bands in an aqueous Triton X-100 micelle solution (pH = 6.9). The resulting oligomers deaggregated by addition of p-toluenesulfonic acid to give monomeric N-protonated ammonium species. The aggregation and deaggregation were dependent on the 31-stereochemistry, indicating that each epimer produced supramolecularly different self-aggregates.

  • RESEARCH ARTICLE: Proteomonas sulcata ACR1: A Fast Anion Channelrhodopsin

    RESEARCH ARTICLE: Proteomonas sulcata ACR1: A Fast Anion Channelrhodopsin

    Natural channelrhodopsins with strictly anion selectivity and high unitary conductance have been recently discovered in the cryptophyte alga Guillardia theta. These proteins, called anion channelrhodopsins (ACRs), are of interest for their novel function and also because they were shown to be highly efficient tools to inhibit neuronal action potentials with light. We show that a homologous protein from the cryptophyte alga Proteomonas sulcata (named here PsuACR1) exhibits similar strict anion selectivity as the previously identified G. theta ACRs. Like G. theta ACRs, PsuACR1 lacks a protonatable residue at the position of the proton acceptor Asp-85 in bacteriorhodopsin, which may be a key characteristic of ACR family members shared by haloarchaeal chloride pumps. Of importance for its potential use in optogenetics, despite its 10-fold lower channel activity than the GtACRs, PsuACR1 exhibits an ~eightfold more rapid channel closing half-time making it uniquely suitable for silencing the subclass of high-frequency firing neurons when high-time resolution is needed. The existence of a rhodopsin with properties similar to G. theta ACRs in a different cryptophyte genus indicates that such proteins may be widespread in the phylum of cryptophyte algae.

  • 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:The Involvement of Splicing Factor hnRNP A1 in UVB‐induced Alternative Splicing of hdm2 (
  • RESEARCH ARTICLE:Stereoselective Self‐Aggregation of 31‐Epimerically Pure Amino Analogs of Zinc Bacteriochlorophyll‐d in an Aqueous Micelle Solution
  • RESEARCH ARTICLE: Proteomonas sulcata ACR1: A Fast Anion Channelrhodopsin
  • 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

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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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