LATTICE MODEL FOR HYDROGEN-BONDING AND HYDRATION IN PURE LIPID BILAYERS

We propose a model for phase transitions involving hydrogen bonding in lipid bilayers. The model is an interacting model with five states on each site of a two-dimensional square lattice. This model describes b oth the hydrogen bonding network proposed for phosphatidylethanolamine lipids by x-ray spectroscopy and its disruption by lipid-water intera ctions. The phase transitions predicted by the model are identified by use of numerical simulation in conjunction with recent extrapolation and finite-size-scaling methods. The percolation properties were also investigated, and it is found that the percolation exponents cannot be described by random percolation theory. The relationship of the resul ts to experiment and extensions of the model is discussed.