Histogram method to obtain heat capacities in lipid monolayers, curved bilayers, and membranes containing peptides

Lipid monolayer chain melting transitions were simulated using a two-state Doniach model, and experimental melting profiles of lipid vesicles were analyzed. We sampled the information of a Monte Carlo simulation into a single broad histogram containing complete information about the distribution of states. The information of the monolayer histogram was first used to calculate the melting behavior of a bilayer constructed from two uncoupled monolayers. We then fitted calorimetric heat profiles of various preparations of dipalmitoyl phosphatidylcholine vesicles. This analysis was extended to lipid bilayers. A fixed mean bilayer curvature was shown to result in a broadening of bilayer melting profiles. We furthermore used the histogram method to obtain the chain melting behavior of simple lipid-peptide mixtures.