[Rotatory mobility and intermolecular reactions of serum albumin studied using the spin-probe method]

Dependence of the rotational mobility of bovine serum albumin on the protein concentration in solution has been studied by means of nitroxyl radical tightly bound to the protein. The rotational correlation time of radical, bound with protein for weak solution has been compared with the theoretical values of correlation times for protein monomer, calculated in terms of its hydration and deviation from the spherical shape. A conclusion about radical orientation relatively to the protein molecule has been drawn from this comparison. The concentration dependence of ratational correlation time for radical, bound with protein, was explained by the protein dimerization in solution. A conclusion has been drawn about the stability of intramolecular structure of serum albumin during its dimerization on the basis of the stability of anisotropic hyperfine constants of adsorbed radical.