A thermodynamic interpretation to formation of clusters at the cell surface.

We develop further the original paper by Gershon, concerning the formation of receptor caps at the cell surface. The phenomenon is interpreted in terms of simple thermodynamic factors like boundary tension and supersaturated concentration of membrane components, within the Gibbs free energy change. The hypothesis that the total number of mol receptors is conserved is a sufficient condition to have a minimum of delta G as a function of the radius of the aggregates. We pay particular attention to effects induced by electrostatic interactions among charged receptor molecules. We discuss extensively the simultaneous formation of N aggregates and the role played by either the electrostatic repulsive forces or boundary tension in controlling the size and the number of stable aggregates. Depending on supersaturation of membrane receptors and in the absence of electric charge up to 50% of solute molecules may condense in a cap-like aggregate.