55 th Anniversary Issue of Photochemistry and Photobiology

This special issue commemorates the 55 Anniversary of Photochemistry and Photobiology. The issue consists of papers from contributors who have had significant ties to the Journal and the American Society for Photobiology (ASP), including former and current editors of the Journal, council members of the ASP, as well as active authors. This commemorative issue consists of 46 papers by these individuals that are located in regions throughout the world, including Argentina, Australia, Brazil, Canada, Chile, China, Czech Republic, France, Germany, Italy, Japan, Norway, Poland, Spain, South Africa, Russia and the United States. Some of the papers explore the photochemistry and photophysics of new sensitizers, fluorophores, natural products, biomolecules and photosynthetic antennas. Other papers describe the photobiology of DNA, RNA, proteins, visual pigments and lipids. Still, other papers explore photobiomodulation, photolyases and photodynamic therapy (PDT), where synergy (i.e., combination therapy) is a common theme. The formation of reactive oxygen species is reported in a number of these papers, such as aqueous media, liposomes and in vitro and in vivo samples. The focus on sensitizers and fluorophores was one facet in this symposium. The contributors include McFarland, Sun et al. who describe synthesis, characterization and photobiological activities of a new series of Ru(II) oligothiophene sensitizers. The study of organic photochemistry includes chiral inductions in photodimerizations as focus of research by Tung et al. and steric influences in the photoenolization of diortho-substituted acetophenones by Gudmundsdottir, Bohne et al. The synthesis and electronic coupling within Pd-phthalocyanine-carotenoid dyads as artificial photosynthetic antennas were the focus of work by Ho, Gust, Moore, Moore et al., including the careful tuning of the triplet-triplet energy transfer, which was also the subject of a highlight piece by Pol ıvka. A detailed photophysical study of the interaction of photoexcited pterin with four of the most reactive amino acids via dynamic and static processes was performed by Thomas et al. Fluorogenic BODIPY-a-tocopherol analogues have been shown by Cosa et al. to be relevant probes for reactive oxygen species. Armitage et al. described the finetuning of the excitation wavelength for thiophene triarylmethane dyes, including fluorescence intensity increases when bound to a protein. Research was also examined by fast spectroscopic techniques to uncover answers to photophysical details including work by Kohler and Crespo-Hern andez. Rochford, Hatamimoslehabadi et al. have probed photoacoustic agents and found that p-bond extended curcumin dyes, in particular naphthyl and thienyl curcuminoids have promise in photoacoustic imaging applications. Another set of articles in this symposium discusses singlet oxygen (O2), which is the main reactive oxygen species generated by the type II photosensitization mechanism. In that respect, Quina et al. reported that pyranoanthocyanins similar to those formed during the aging of red wines have fairly long triplet lifetimes and are thus generators of O2 in acetonitrile, although their capacity to generate O2 is dampened in aqueous and acid media. Thomas, McFarland, Greer et al. provided insight with a U-shaped design for sensitizer drug photorelease using O2 as the cleaving agent. Other fair sources of O2 consist of functionalized fullerenes and surface TiO2 nanoparticles that were shown by Sarna et al. to trigger upon excitation lipid peroxidation. Type II photosensitized reactions of cholesterol, a relevant PDT target, that give rise to three isomeric hydroperoxides are critically surveyed by Girotti et al. in an extensive review article that is highlighted by Chiemezie and Greer. The relevance of using uric acid as a probe of O2 that may vary according to experimental conditions has been revisited by Ogilby et al. Photobiochemistry of isolated and cellular DNA was also a significant focus in this symposium. Taylor et al. and Shafirovich, Geacintov et al. reported the reactivity of G-quadruplex model structures of human telomere sequences to UVB-induced crosslink formation and photosensitized one-electron oxidation, respectively. The main one-electron oxidation reactions of isolated and cellular DNA triggered by biphotonic ionization of pyrimidine and purine bases were reviewed by Cadet et al. It has been demonstrated by Ahmad et al. that nicotinamide exerts a protective role against DNA damage induced by UVB and UVA irradiation of melanocytes. Other important cellular targets investigated include lipids and proteins. In contrast to recent claims, it was found by Douki et al. that 6-formylindolo[3,2-b] carbazole (FICZ) is generated as a minor photoproduct of tryptophan by either UVB radiation or simulated sunlight. DNA repair is essential for maintaining genome integrity. Nishigori et al. have provided a survey of the characteristics of Japanese xeroderma pigmentosum patients who suffer from deficiencies in the DNA repair of bulky bipyrimidine photoproducts. Albaraccin et al. have isolated photoactive proteins as putative photolyases/cryptochromes that confer high UV-resistance to bacteria from Andean lakes. Various biological responses of bacteria and human cells to UV components of solar radiation have been the focus of articles. Beardall and Islam reported a dependence of UV-sensitivity of cyanobacteria on temperature according to the strains. Menck et al. demonstrated that the ATR/chk1 pathway is activated by oxidative reactions triggered by UVA radiation in xeroderma pigmentosum variant cells. Wu and Zhao have shown that post-UVBinduced release of nitric oxide from endothelial cells promotes the transformation of keratinocytes. Nanomolar phototoxicity of 1,9DOI: 10.1111/php.13069 © 2019 The American Society of Photobiology This preface is part of a Special Issue celebrating Photochemistry and Photobiology’s 55 Anniversary.