A swollen gel phase of DPPC aqueous solution with small amount of ethanol observed at moderate pressure and temperature

Abstract

In order to clarify effects of pressure on phospholipids, small-angle neutron scattering and X-ray scattering experiments on an aqueous solution of dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) with small amount of ethanol were carried out. At moderate temperature and pressure (41 ≤ T ≤ 60°C and 10 ≤ P ≤ 80 MPa), among a fluid lamellar (Lα) phase, a ripple gel (Pα′) phase and an interdigitated gel (LβI) phase, we have found a new phase with a single peak at around Q = 0.06 Å−1. This phase was characterized to be a swollen gel phase from the data analysis. The kinetics of the phase transition to the LβI phase was investigated, and the relaxation was much slower than the transition to the other bilayer structures.