[Salt ion interaction with the protein molecule: the facts and the concept]

The effect of salt concentration and its nature on some properties of alpha-chymotrypsin (the catalytic activity, the solution optical density, the sedimentation coefficient) has been considered. The limiting stage of enzyme-salt interaction has been shown to change with the variation of experimental conditions. As salt concentration increases the surface electrostatic interaction of salt ions with the enzyme molecule changes by ions penetration via certain channels within the protein globule and their subsequent binding to regulatory centers. The difference in ions nature and binding centers provides the variety of modifications observed. At high salt concentrations the solvent structure becomes predominant.