Small angle neutron scattering and calorimetric studies of large unilamellar vesicles of the phospholipid dipalmitoylphosphatidylcholine

High-resolution differential scanning calorimetry (DSC) and small angle neutron scattering (SANS) experiments have been conducted on large unilamellar vesicles (LUV’s) of the phospholipid dipalmitoylphosphatidylcholine (DPPC) in excess water. The DSC results indicate a phase transition at temperatures corresponding to the gel ${(L}_{{\beta }^{\prime }})$ to ripple ${(P}_{{\beta }^{\prime }})$ phase transition seen in multilamellar vesicles of DPPC while the SANS experiments provide direct evidence for the formation of the $P_{{\beta }^{\prime }}$ phase in these systems. In addition, it is shown that SANS is an effective technique for extracting structural parameters such as vesicle radius and thickness in LUV model membrane systems.