A Role for Ion Association and Polymer Elasticity in Bioenergetics

This paper interprets some of the complex energy transducing reactions of lipoprotein biochemical membranes in terms of macromolecular science. The processes considered involve ion (or electron)-exchange membrane reactions. Dilation of the membrane through osmosis and electrostatic repulsion at the exchange sites are opposed by a contraction which is postulated to arise from the presence of rubber like lipid bilayers. A change in the elasticity of the membrane alters the dilation-contraction equilibrium and modifies the ion interaction energies at the exchange sites. The elasticity is regulated by swelling interactions of the bilipids with control substances and, in some systems, by reversible cross-linking reactions. The latter can involve thioester cross-links, formed in reversible reactions with ATP, or various types of salt-links formed in association with ion concentration gradients across the membrane. Energized formation of the cross-links can oppose the dilation and change the ion selectivities reversibly. Such systems can therefore transfer energy reversibly between participants in the contractile and dilatory processes.

Such a concept can explain the operation of some membrane pumps, oxidative phosphorylation, action potentials, and some sensory receptors.