The effect of lateral mobility on the binding and reaction rate at membrane sites.

The rates of membrane processes like transport, hormone action and enzyme reaction depend on the prevailing temperature. Arrhenius plots of such rates show a break at the phase transition temperature. We have very little insight into the molecular mechanism of the effect of phase transition on the membrane phenomena. In general above this temperature there is an onset of two dimensional mobility of the surface sites. Here, we point out that the binding of ligands to these sites should then be described by an adsorption isotherm appropriate for mobile rather than fixed sites. This introduces an additional factor in the rate equation, which correlates well with the observed changes in the rates at membrane sites on gel to liquid crystalline transition.