Roy S, Gruenbaum S M, Skinner J L
Theoretical Chemistry Institute and Department of Chemistry, 1101 University Ave., University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
J Chem Phys. 2014 Dec 14;141(22):22D505. doi: 10.1063/1.4895968.
The structural stability and function of biomolecules is strongly influenced by the dynamics and hydrogen bonding of interfacial water. Understanding and characterizing the dynamics of these water molecules require a surface-sensitive technique such as two-dimensional vibrational sum-frequency generation (2DSFG) spectroscopy. We have combined theoretical 2DSFG calculations with molecular dynamics simulations in order to investigate the dynamics of water near different lipid and surfactant monolayer surfaces. We show that 2DSFG can distinguish the dynamics of interfacial water as a function of the lipid charge and headgroup chemistry. The dynamics of water is slow compared to the bulk near water-zwitterionic and water-anionic interfaces due to conformational constraints on interfacial water imposed by strong phosphate-water hydrogen bonding. The dynamics of water is somewhat faster near water-cationic lipid interfaces as no such constraint is present. Using hydrogen bonding and rotational correlation functions, we characterize the dynamics of water as a function of the distance from the interface between water and zwitterionic lipids. We find that there is a transition from bulk-like to interface-like dynamics approximately 7 Å away from a zwitterionic phosphatidylcholine monolayer surface.
生物分子的结构稳定性和功能受到界面水的动力学和氢键的强烈影响。理解和表征这些水分子的动力学需要一种表面敏感技术，如二维振动和频产生（2DSFG）光谱。我们将理论2DSFG计算与分子动力学模拟相结合，以研究不同脂质和表面活性剂单分子层表面附近水的动力学。我们表明，2DSFG可以区分界面水的动力学作为脂质电荷和头基化学的函数。由于强磷酸盐 - 水氢键对界面水施加的构象限制，与水 - 两性离子和水 - 阴离子界面附近的本体相比，水的动力学较慢。在水 - 阳离子脂质界面附近，水的动力学稍快，因为不存在这样的限制。使用氢键和旋转相关函数，我们将水的动力学表征为水与两性离子脂质之间界面距离的函数。我们发现，在距两性离子磷脂酰胆碱单分子层表面约7 Å处，存在从本体样到界面样动力学的转变。
