[Effect of media composition on properties of polydisulfide bioantioxidants]

Characteristics of polydisulfides of gallic acid (PDSG), 2-amino-4-nitrophenol (PDSANP), and biuret (PDSB) depending on the composition of the aqueous medium were studied. In contrast to PDSANP and PDSB, there was oxidation of PDSG with accumulation of products of polydisulfide transformation in the medium. The rate of PDSG autoxidation depended on pH, concentration of polydisulfide and buffers, and increased at high pH. The rate of oxidation significantly increased if addition of dimethylformamide and/or ethanol in the medium or solubilization of polydisulfide with cetyltrimethylammonium bromide, surface-active compound (SAC), prevented the association of PDSG. Decreasing pH of the solution and adding ovalbumin and/or Triton X-100 to the medium can decrease the rate of autoxidation of PDSG in aqueous medium. Exogenous H2O2 inhibited the oxidation of PDSG. The secondary structure of catalase was changed by PDSG. Electrical conductivity of PDSG and PDSANP solutions was studied. Possible mechanisms of PDSG autoxidation and polydisulfides-protein interaction due to forces of cooperative electrostatic interaction, thiol-disulfide exchanges and nucleophilic replacements were discussed.