The intermolecular interactions that result in the formation of plasma membrane inner leaflet cholesterol domains were investigated with model membrane systems. Systematic experiments of Langmuir monolayers of saturated and unsaturated phosphatidylserines (PS) with varying mole percent of cholesterol were analyzed by excess free energy, ideal mixing, and compression modulus. Cholesterol was found to have the largest condensing effect on dipalmitolyphosphatidylserine (DPPS) monolayers at 25 mol% cholesterol, evident by the  -15.9% difference from ideal mixing, the increase in compression modulus, and the -194 kJmol-1 free energy calculated for the system. Dioleoylphosphatdylserine (DOPS) monolayers were expanded in area for all mol percentages of cholesterol investigated (20, 25, 30, and 33) while the compression modulus was increased due to interactions between the PS and cholesterol headgroups. The expansion in area is hypothesized to be due to the steric effects between the unsaturated phospholipid tailgroups and the steroidal ring of the cholesterol molecule.

Phosphatidylserine model membrane studies for the investigation of cholesterol domain formation in the plasma membrane inner leaflet

247th National Meeting (2014)

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