Water-lipid interface in lipidic mesophases with excess water

This study investigates the influence of excess water on the lipidic mesophase during the phase transition from diamond cubic phase (Pn3m) to reverse hexagonal phase (HII). Using a combination of small angle X-ray scattering (SAXS), broadband dielectric spectroscopy (BDS), and Fourier transform infrared (FTIR) techniques, we explore the dynamics of lipids and their interaction with water during phase transition. Our BDS results reveal three relaxation processes originating from lipids, all of which exhibit a kink during the phase transition. With the excess water, these processes accelerate due to the plasticizing effect of water. Additionally, our results demonstrate that the headgroups in the HII phase are more densely packed than those in the Pn3m phase, which agrees with the FTIR results. Meanwhile, we investigate the influence of excess water on the lipid headgroups, the H-bond network of water, the lipid tail, and the interface carbonyl group between the head and tail of the lipid molecule. The results indicate that excess water permeates the lipid interface and forms additional hydrogen bonds with the carbonyl groups. As a result, the headgroups are more flexible in a lipidic mesophase with excess water than those in mesophases without excess water. We study the influence of excess water on the phase transition of lipidic mesophases from the cubic to reverse hexagonal phase. Excess water permeates the interface and forms additional hydrogen bonds with lipids, accelerating the lipid dynamics.

Automated summary

This study investigates the influence of excess water on the lipidic mesophase during the phase transition. The results show that excess water accelerates the lipid dynamics and forms additional hydrogen bonds, making the headgroups more flexible in the presence of excess water.