Ishiyama Tatsuya, Terada Daichi, Morita Akihiro
Department of Applied Chemistry, Graduate School of Science and Engineering, University of Toyama , Toyama 930-8555, Japan.
Department of Chemistry Graduate School of Science, Tohoku University , Sendai 980-8578, Japan.
J Phys Chem Lett. 2016 Jan 21;7(2):216-20. doi: 10.1021/acs.jpclett.5b02567. Epub 2015 Dec 31.
Interface structure of water/[3-palmitoyl-2-oleoyl-D-glycero-1-phosphatidylcholine] (POPC) lipid layer is investigated with molecular dynamics (MD) simulation by analyzing the recent heterodyne-detected vibrational sum-frequency generation (HD VSFG) spectroscopy. The MD simulation clearly reproduced the experimental HD VSFG spectrum of imaginary susceptibility (Im[χ]), which exhibits two positive bands in the OH stretching vibrations of water. With the help of decomposition MD analysis, we found three kinds of interfacial water in relation to the HD VSFG spectrum. The low-frequency positive band is attributed to the water pointing toward the lipid side, whose orientation is influenced by negatively charged phosphate and positively charged choline of POPC. The high-frequency positive band is attributed to the water bonding with the carbonyl groups of the lipid. The gap between the two positive bands indicates the interfacial water pointing toward the bulk water phase in the vicinity of the choline groups.
通过分析最近的外差检测振动和频产生（HD VSFG）光谱，利用分子动力学（MD）模拟研究了水/[3-棕榈酰-2-油酰-D-甘油-1-磷脂酰胆碱]（POPC）脂质层的界面结构。MD模拟清晰地再现了虚部磁化率（Im[χ]）的实验HD VSFG光谱，该光谱在水的OH伸缩振动中呈现出两个正峰。借助分解MD分析，我们发现了与HD VSFG光谱相关的三种界面水。低频正峰归因于指向脂质一侧的水，其取向受POPC带负电的磷酸基团和带正电的胆碱基团影响。高频正峰归因于与脂质羰基结合的水。两个正峰之间的间隙表明在胆碱基团附近指向本体水相的界面水。
