[Measurement of specific surface energy of protein hydration shell using ESR of spin label]

An approach to determining the microscopic surface tension in water-protein matrix using EPR of spin label was developed. The approach in based on the use of viscosity isotherms of correlation time of spin labels bound to the protein macromolecule. Changes in specific surface tension of spin-labeled molecules of serum albumin, hemoglobin, and antibodies were studied depending on protein concentration, the structure of the reporter group, ligand state of the protein, and the presence of salts, water-soluble polymers, and D2O. Possible reasons of microscopic changes in surface tension are discussed.