[Dynamic model of protein behavior in water]

In the basis of the suggested model lies the hypothesis that during the evolution process biological macromolecules "learnt" to use the ability of water through cooperative transition from the rigid phase to the liquid one without a change in free energy for the regulation of their conformation. In accordance with the results of a number of investigations it is assumed that the protein molecule exists in thermodynamic equilibrium between two conformers with different accessibilities of nonpolar cavities to water and with different effective volumes. Deformation of both or one of the conformers under the effect of specific or nonspecific influences removes the system (protein+water) from the equilibrium, and as a result of the relaxation process the system achieves a new equilibrium state. A change in the equilibrium constant between the conformers determines the change of the average protein volume. The entropy and entalpy of protein and water in the system (protein+water) change during this process in a counterphase manner. Phase transition of water, involved between the subunits of oligomeric protein, may play a significant role in the mechanisms of allosteric effects.