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Electron Paramagnetic Resonance and Spin Trapping Investigations of the Photoreactivity of Human Lens Proteins
Author(s) -
Dillon James,
Ortwerth Beryl J.,
Chignell Colin F.,
Reszka Krzysztof J.
Publication year - 1999
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1999.tb03284.x
Subject(s) - chemistry , ascorbic acid , electron paramagnetic resonance , spin trapping , cysteine , glutathione , photochemistry , radical , adduct , chromophore , covalent bond , biochemistry , organic chemistry , enzyme , nuclear magnetic resonance , physics , food science
— Oxidation of cysteine, glutathione and ascorbate by photoexcited proteins from normal and cataractous lenses was investigated using electron paramagnetic resonance in combination with spin trapping. We report that illumination of these proteins in pH 7 buffer with light >300 nm in the presence of thiols (RSH) and a spin trap 5,5‐dimethyl‐1‐pyrroline N ‐oxide (DMPO), afforded DMPO/S‐cysteine and DMPO/G adducts, suggesting the formation of the corresponding thiyl radicals. In a nonbufered aqueous solution, illumination of the proteins and glutathione also produced superoxide detected as a DMPO/O 2 H adduct. Irradiation of these proteins in the presence of ascorbate generated ascorbate radical. We conclude that chromophores present in the natural normal and cataractous lenses are capable of initiating photooxidative processes involving endogenous thiols and ascorbic acid. This observation may be pertinent to UV‐induced development of cataract.