WETTING AND CAPILLARY CONDENSATION AS MEANS OF PROTEIN ORGANIZATION IN MEMBRANES

Wetting and capillary condensation are thermodynamic phenomena in whic h the special affinity of interfaces to a thermodynamic phase, relativ e to the stable bulk phase, leads to the stabilization of a wetting ph ase at the interfaces. Wetting and capillary condensation are here pro posed as mechanisms that in membranes may serve to induce special lipi d phases in between integral membrane proteins leading to long-range l ipid-mediated joining forces acting between the proteins and hence pro viding a means of protein organization. The consequences of wetting in terms of protein aggregation and protein clustering are derived both within a simple phenomenological theory as well as within a concrete c alculation on a microscopic model of lipid-protein interactions that a ccounts for the lipid bilayer phase equilibria and direct lipid-protei n interactions governed by hydrophobic matching between the lipid bila yer hydrophobic thickness and the length of the hydrophobic membrane d omain. The theoretical results are expected to be relevant for optimiz ing the experimental conditions required for forming protein aggregate s and regular protein arrays in membranes.