Interbilayer cluster-cluster interaction in multilamellar vesicles: thermodynamic approach.

A simple thermodynamic model of the main transition in pure lipid bilayers is presented. The basic relations for cooperativity, aggregation degree and fractional number of molecules are derived. The experimental heat capacity measurements of uni- and multilamellar phospholipid vesicles are analysed within the context of this model, and the transition characteristics are obtained. It is demonstrated that they differ from each other, and these differences are discussed according to the system configuration. The derived cluster configuration entropy supports the idea of strong interbilayer cluster-cluster cooperation.