A COMPARATIVE STUDY OF PHOTODYNAMIC OXIDATION AND RADIOFREQUENCY‐DISCHARGE‐GENERATED ¹O₂ OXIDATION OF GUANOSINE

Abstract

Guanosine-2JC and guano~ine-8-~Y3 were subjected, under similar environmental conditions, to oxidation either by radiofrequency-discharge-generated singlet oxygen or by a methyleneblue-sensitized photodynamic reaction. The reaction products in both cases were compared chromatographically. The product distributions were not identical, indicating differing modes of oxidation in these two systems. It is suggested that both Type I and Type I1 oxidation mechanisms are operative in the photodynamic system, whereas only Type 11-like reactions occur in the radio-frequency-discharge system.

Extracellular Polysaccharide Production in a Scytonemin-Deficient Mutant of Nostoc punctiforme Under UVA and Oxidative Stress

“…Self-shading of the cultures was minimized by filtering cells onto 90-mm membrane filters (EMD Millipore, Billerica, MA, USA) that were allowed to float on top of liquid growth media in glass Petri plates [32]. To induce oxidative stress, filtered cultures were exposed to 2 lM methylene blue and to minimize methylene blue consumption, filters were transferred to fresh media with 2 lM methylene blue daily for all 6 days of the experiment [9,21]. All experiments were done in triplicate and control cultures for each variable were also grown under standard conditions in the absence of UVA and methylene blue.…”

Singlet Oxygen Induces Frank Strand Breaks as Well as Alkali‐ and Piperidine‐labile Sites in Supercoiled Plasmid Dna

“…A major advantage of this system is that it produces pure singlet oxygen uncontaminated by other possible reactive species, clearly demonstrated by the excellent agreement between the theoretical and observed dependences of effect upon the distance between generating surface and target solution ). In contrast, photosensitization with soluble dyes can produce reactive intermediates such as the excited state sensitizer and forms of reactive oxygen whose effects are difficult to distinguish from those of singlet oxygen (Kornhauser et al, 1973;Saito et al, 1975;Cadet and Teoule, 1978;Peak et al, 1984). Soluble chemical sources of singlet oxygen (Schapp and Bartlett, 1970;Saito and Matsuura, 1981) may provide relatively pure single oxygen, but are themselves oxidants and can react with certain substrates.…”

Photooxygenation of Methyl Linoleate Sensitized by Porphyrins and Dyes in Acetonitrile Solution and Aqueous Emulsion Systems

“…Recently there has been increasing interest in application of the photodynamic action to a tumor phototherapy using hematoporphyrin derivatives as the potent sensitizers (Kelly and Snell, 1976;Dougherty et al, 1977). Lipid esters of polyunsaturated fatty acids constituting cell membrane (Lamola et al, 1973;Doleiden et al, 1974;Fahrenholtz et al, 1974), as well as intracellular DNA (Simon and Van Vunakis, 1962;Sussenbach andBerends, 1964, 1965;Hallett et al, 1970;Kornhauser et al, 1973;Elad, 1976), have been *To whom correspondence should be addressed. tAbbrevratrons: AF, acriflavine; AO, acridine orange; HP, hematoporphyrin IX; MB, methylene blue; ML-H, methyl linoleate; ML-OOH, methyl hydroperoxylinoleate; 9-tc, methyl 9-hydroperoxy-10-trans.12-cis-octadecadienoate ; 9-tt, methyl 9-hydroperoxy-1 0-trans, 17-trans-oetadecadienoate; RB, rose bengal; Sen, sensitizer; lO-OOH, methyl 10-hydroperoxy-8,12-octadecadienoate; 1 2 -0 0 H , methyl 12-hydroperoxy-9,13-octadecadienoate; 13-ct. methyl 13-hydroperoxy-9-cis,ll-truns-oi:tadecadienoate; 13-tt, methyl 13-hydroperoxy-9-trans,ll-frans-octadecadienoate; ZnTMPyP, zinc tetrakis(N-methyl-4-pyri-diniumy1)porphyrin.…”