Simon S A, McIntosh T J
Department of Neurobiology, Duke University Medical Center, Durham, NC 27710.
Proc Natl Acad Sci U S A. 1989 Dec;86(23):9263-7. doi: 10.1073/pnas.86.23.9263.
As polar surfaces in solvent are brought together, they experience a large repulsive interaction, termed the solvation pressure. The solvation pressure between rough surfaces, such as lipid bilayers, has been shown previously to decay exponentially with distance between surfaces. In this paper, we compare measured values of the solvation pressure between bilayers and the dipole potential for monolayers in equilibrium with bilayers. For a variety of polar solvents and lipid phases, we find a correlation between the measured solvation pressures and dipole potentials. Analysis of the data indicates that the magnitude of the solvation pressure is proportional to the square of the dipole potential. Our experiments also show that the oriented dipoles in the lipid head-group region, including those of both the lipid and solvent molecules, contribute to the dipole potential. We argue that (i) the field produced by these interfacial dipoles polarizes the interbilayer solvent molecules giving rise to the solvation pressure and (ii) both the solvation pressure and the dipole potential decay exponentially with distance from the bilayer surface, with a decay constant that depends on the packing density of the interbilayer solvent molecules (1-2 A in water). These results may have importance in cell adhesion, adsorption of proteins to membranes, characteristics of channel permeability, and the interpretation of electrokinetic experiments.
当溶剂中的极性表面相互靠近时，它们会经历一种强烈的排斥相互作用，称为溶剂化压力。先前已表明，粗糙表面（如脂质双层）之间的溶剂化压力会随着表面间距离呈指数衰减。在本文中，我们比较了双层膜之间溶剂化压力的测量值以及与双层膜处于平衡状态的单层膜的偶极势。对于多种极性溶剂和脂质相，我们发现测量的溶剂化压力与偶极势之间存在相关性。数据分析表明，溶剂化压力的大小与偶极势的平方成正比。我们的实验还表明，脂质头部基团区域中的定向偶极，包括脂质和溶剂分子的偶极，都对偶极势有贡献。我们认为：（i）这些界面偶极产生的场使双层间溶剂分子极化，从而产生溶剂化压力；（ii）溶剂化压力和偶极势都随着与双层表面距离的增加呈指数衰减，衰减常数取决于双层间溶剂分子的堆积密度（在水中为1 - 2埃）。这些结果可能在细胞黏附、蛋白质在膜上的吸附、通道通透性特征以及电动实验的解释方面具有重要意义。
