SUSCEPTIBILITY OF GAMMA-IRRADIATED PROTEINS TO IN-VITRO GLYCATION - EXPOSURE TO OXYGEN-FREE RADICALS INCREASES GLYCATION-INDUCED MODIFICATIONS

Oxidation and glycation are non-enzymatic protein modifications involv ed in the pathogenesis of aging. We evaluated their possible influence s in an in vitro system: albumin was oxidized by gamma-irradiation and then exposed to glycation in vitro. Fluorescence modifications were a nalysed as signals of protein alterations. Both radiolytic oxidation a nd in vitro glycation provoked a sharp decrease of tryptophan fluoresc ence (278 nn ex./340 nm em.); their effects tended to be additive, unl ess a saturation limit was reached. Both individually and in combinati on, these two non-enzymatic processes induced the appearance of a new fluorescence (335 Mn ex./415 nm em.); in this case as well there was a n additive effect, with a trend toward saturation. Radiolytic oxidatio n and in vitro glycation seem to provoke similar damage to the exposed proteins: the observed fluorescence alterations may be due to similar conformational changes, breaks or the development of fluorophores.