Abstract The vibrational spectra of interfacial water at phospholipid bilayers is critical to the understanding of cell membrane functions. In this work, we employ molecular dynamics simulations to explore simultaneous responses in both mid- and far-Infrared (IR) spectra of water at the interface with 3-palmitoyl-2-oleoyl- d -glycero-1-phosphatidyl choline (POPC) bilayers. Our results show that the interfacial water can exhibit both a red shift in the mid-IR region for the O–H stretching mode and a blue shift in the far-IR region due to the vibrational mode of water-water hydrogen bonds (HBs). More interestingly, our simulation results reveal that such shifts in both mid- and far-IR regions are essentially induced by the interfacial water molecules that form HBs with the POPC. In particular, the HBs between the interfacial water and the POPC are strong, especially for those with the non-bridging oxygen atoms connecting the phosphorus atom. Such preferential leads to the considerably enhanced HB strength which in return promotes shifts in the mid- and far-IR regions.

中文翻译：

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磷脂双分子层界面水的中远红外光谱中氢键诱导的响应

摘要 磷脂双分子层界面水的振动光谱对于理解细胞膜功能至关重要。在这项工作中，我们采用分子动力学模拟来探索水与 3-棕榈酰-2-油酰-d-甘油-1-磷脂酰胆碱 (POPC) 界面处的中红外和远红外 (IR) 光谱的同时响应双层。我们的结果表明，由于水 - 水氢键（HBs）的振动模式，界面水可以在中红外区域呈现 O-H 拉伸模式的红移和远红外区域的蓝移. 更有趣的是，我们的模拟结果表明，中红外区域和远红外区域的这种变化基本上是由与 POPC 形成 HBs 的界面水分子引起的。特别是，界面水和POPC之间的HBs很强，特别是对于那些与磷原子连接的非桥连氧原子的HBs。这种优先导致显着增强的 HB 强度，反过来又促进了中红外区域和远红外区域的转变。