[Isotherms of globular protein hydration under dynamic conditions]

The hydration isotherms of alpha-chymotrypsin, lysozyme, pork insulin, pork pepsin and serum albumin were obtained by means of dynamic method. The values of BET-monolayers for processes of water sorption leads to (h) and desorption comes from (h) do not depend on the static or dynamic way of achieving of hydration equilibrium in spite of difference in the shape of isotherms. The values of comes from h for proteins with known tertiary structure (alpha-chymotrypsin, lysozyme and insulin) coinside with the number of exposed polar amino acid side chains. The lowering of leads to h values in comparison with comes from h is correlated with inability of omega-amido groups of Asn and Gln residues and of ion pair-forming residues to take part in the formation of sorptive BET-monolayer. These rules for the interpretation of hydration isotherms were used to evaluate the numbers of exposed and buried polar side chains in proteins with unknown tertiary structure--pepsin and serum albumin.