Wolfe D H, Brockman H L
Hormel Institute, University of Minnesota, Austin 55912.
Proc Natl Acad Sci U S A. 1988 Jun;85(12):4285-9. doi: 10.1073/pnas.85.12.4285.
A quasi-two-dimensional equation of state for liquid-type lipid monolayers has been derived and successfully applied to surface pressure-area isotherms obtained with a variety of lipids. For lipids with acyl moieties of similar length, the surface pressure and area at monolayer collapse can be accurately predicted from data obtained at lower surface pressure. Consideration of the rationalized activity coefficient as a linear scaler in an expression for surface pressure as a function of depth in the surface phase permits comparison of surface pressure-area data for monolayers with force-distance data for bilayers. This analysis shows the thermodynamic equivalence of monolayers at collapse and fully hydrated bilayers. It also supports the interpretation of the activity coefficient as a scaler and allows its determination solely from bilayer-derived data. Overall, the results show the common assumption that partial specific volume of water equals its bulk value to be inappropriate for the analysis of surface structure.
已推导得出一种用于液态脂质单层的准二维状态方程，并成功应用于多种脂质的表面压力-面积等温线。对于具有相似长度酰基部分的脂质，单层崩塌时的表面压力和面积可根据较低表面压力下获得的数据准确预测。将合理的活度系数视为表面相中深度函数的表面压力表达式中的线性标度，使得单层的表面压力-面积数据与双层的力-距离数据能够进行比较。该分析表明崩塌时的单层与完全水合的双层在热力学上是等效的。这也支持将活度系数解释为标度，并允许仅从双层衍生数据来确定它。总体而言，结果表明水的偏比容等于其体相值这一常见假设不适用于表面结构分析。
