[Study of the flexibility of serum albumin molecules using the spin label method].

In is shown that the description of the motion character of N.- O-group of spin label conjugated with human serum albumin molecule on the basis of the jump--way isotropic diffusion model is correct. The structural flexibility of serum albumin molecule was revealed. It is the result of the ability of three domains that form the molecule for relative thermal reorientations. General tendency of elevation of protein correlation time from 20 to 45 ns with rising temperature from 5 to 44 degrees reflects the strengthening of hydrophobic interactions between domains. The presence in solution of 5 and 15% D2O essentially increases the amplitude of protein flexibility changes in the range of two thermoinduced transitions of serum albumin: 15-20 degrees and 32-35 degrees C. It reflects the important role of water in this process.