Conformational effects of interaction of serum albumine with nanoparticles of carbon shungyte: epr spin-probe study

Conformational effects of interaction between bovine and human serum albumin (SA) molecules and nanoparticles of shungite carbon (ShC) in aqueous dispersion have been studied in the temperature range 17 – 72 ° С K using electron spin resonance (EPR) spin probing (P). The temperature and kinetic dependences of the parameters of the EPR spectrum for solutions and dispersions of SA and ShC as well as for their mixtures have been obtained. The interaction of SA molecules with ShC nanoparticles has been shown to affect significantly the thermally induced protein conformational changes that determine the ability of the SH group of Cys-35 of SA to convert the NO group of the doxyl stearic fatty acid (FA) used as the probe to diamagnetic state. The temperature transitions reflecting the SA conformational changes in the localization region of P become less pronounced and shift toward higher temperatures in the presence of ShC. This may be due to a change in the oxidation-reduction balance of the set of SA molecules in solution or dispersion, since ShC acts as an oxidant with respect to SA. Therefore, ShC can also be considered an agent affecting the degree of oxidation of Cys-34 of SA with free radicals, such as P. ShC nanoparticles and P compete with each other during the oxidation of Cys-34. Furthermore, the transfer of P from SA to nanoparticles is facilitated due to the conformational transitions, and the reduction of the probe NO group by the protein SH groups is impeded. This allows considering ShC nanoparticles a factor of regulation of the redox balance in systems involving SA, including physiological media.