Molecular Machines: How Motion and Other Functions of Living Organisms Can Result from Reversible Chemical Changes

Abstract

Certain model proteins dramatically fold and become more ordered on raising the temperature. When the temperature is raised to drive folding and assembly, these model proteins can lift weights and perform work; they can produce motion. The temperature of warm‐blooded animals, however, is kept constant. Therefore, motion cannot result from a change in temperature. In this case, a free energy change, caused, for example, by an increase in the concentration of a chemical, can lower the temperature at which the protein folding and assembly transition occurs from above to below physiological temperature. Raising the concentration of a chemical isothermally has indeed been shown to result in motion and the efficient performance of work. These model proteins and the mechanism they reveal provide insight into the molecular basis for diverse biological functions; they are models for the molecular machines that comprise the living organism, and they provide a new class of materials for both medical and nonmedical applications.