title: Crosslinking and photoreaction of ozone-oxidized calf-lens alpha-crystallin.
abstract: Direct-photo-oxidation, singlet oxygen-oxidation, or photosensitized oxidation can modify lens crystallins, causing an increase in blue fluorescence and covalent crosslinking. A relationship between these changes has not been elucidated. We now report results from experiments with ozone oxidation. When calf-lens alpha-crystallin is treated with zone oxidation. When calf-lens alpha-crystallin is treated with ozone, new absorption, fluorescence, and phosphorescence, which are characteristic of the oxidized product of tryptophan (N-formylkynurenine), appear at 320, 435, and 445 nm, respectively. In addition, in this ozonization of alpha-crystallin, its polypeptides are crosslinked by nondisulfide bonds. Irradiation of ozone-treated alpha-crystallin with near-ultraviolet (365 nm) light increases crosslinking and reduces the 320 nm absorbance with a concomitant appearance of a new absorption at about 420 nm. This photoproduct exhibits an intense fluorescence around 450 nm and a weak phosphorescence at 510 nm, with excitation peaks at 400, 415, and 422 nm. These findings are essentially the same as those observed in photo-oxidized alpha-crystallin, suggesting the involvement of the same tryptophan oxidized product in the modification of the lens protein.
mesh_terms: D000818:Animals; D002417:Cattle; D003459:Crystallins / Q000032:analysis* / Q000528:radiation effects; D005453:Fluorescence; D066298:In Vitro Techniques; D007737:Kynurenine / Q000031:analogs & derivatives / Q000032:analysis; D007908:Lens, Crystalline / Q000032:analysis* / Q000187:drug effects; D008027:Light; D008163:Luminescent Measurements; D010084:Oxidation-Reduction; D010126:Ozone / Q000494:pharmacology; D010777:Photochemistry
chemical_list: D003459:Crystallins; C007772:N'-formylkynurenine; D007737:Kynurenine; D010126:Ozone