Yao Yang, Catalini Sara, Foggi Paolo, Mezzenga Raffaele
Department of Health Sciences and Technology, ETH Zürich, 8092 Zürich, Switzerland.
European Laboratory for Non-Linear Spectroscopy, LENS, 50019 Florence, Italy.
Faraday Discuss. 2024 Feb 6;249(0):469-484. doi: 10.1039/d3fd00118k.
This study investigates the influence of excess water on the lipidic mesophase during the phase transition from diamond cubic phase (3̄) to reverse hexagonal phase (). 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 phase are more densely packed than those in the 3̄ 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.
本研究调查了在从金刚石立方相（3̄）到反六角相（）的相变过程中，过量水对脂质中间相的影响。通过结合小角X射线散射（SAXS）、宽带介电谱（BDS）和傅里叶变换红外（FTIR）技术，我们探索了相变过程中脂质的动力学及其与水的相互作用。我们的BDS结果揭示了源自脂质的三个弛豫过程，所有这些过程在相变过程中都出现了一个拐点。随着过量水的存在，由于水的增塑作用，这些过程加速。此外，我们的结果表明，相比3̄相，相中的头基堆积更紧密，这与FTIR结果一致。同时，我们研究了过量水对脂质头基、水的氢键网络、脂质尾部以及脂质分子头部和尾部之间的界面羰基的影响。结果表明，过量水渗透到脂质界面并与羰基形成额外的氢键。因此，与没有过量水的中间相相比，在含有过量水的脂质中间相中头基更具柔韧性。
