Susceptibility of Gamma‐Irradiated Proteins to In Vitro Glycation: Exposure to Oxygen Free Radicals Increases Glycation‐Induced Modifications

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Abstract
Oxidation and glycation are non‐enzymatic protein modifications involved in the pathogenesis of aging. We evaluated their possible influences in an in vitro system: albumin was oxidized by gamma‐irradiation and then exposed to glycation in vitro. Fluorescence modifications were analysed as signals of protein alterations. Both radiolytic oxidation and in vitro glycation provoked a sharp decrease of tryptophan fluorescence (278 nm ex./340 nm em.); their effects tended to be additive, unless a saturation limit was reached. Both individually and in combination, these two non‐enzymatic processes induced the appearance of a new fluorescence (335 nm ex./415 nm em.); in this case as well there was an additive effect, with a trend toward saturation. Radiolytic oxidation 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.
Funding Information
  • CNR, MURST (93.00407 PF40 "Invecchiamento" code no. 95 3 532)