On the role of the macromolecular phase transitions in biology in response to change in solution volume or macromolecular composition: action as an entropy buffer

We have used numerical simulation to demonstrate the potential for macromolecular precipitate solution phase transitions existing within the cell, to play a role in the minimization of changes in location or quaternary state of other macromolecular components, predicted to accompany changes in cell volume. For our modeling we have employed thermodynamic relations that take into account the large effects upon the thermodynamic activity coefficient produced by a solution environment that is highly volume occupied due to the presence of high concentrations of soluble macromolecule. The theoretical approach adopted, along with the simulated results, provide a framework for the interpretation of certain proteins' behavior (e.g. cytoskeletal elements such as tubulin and actin and possibly some prion structures) in response to cell volume change. (C) 2002 Elsevier Science B.V. All rights reserved.