Abstract—

Compression diagrams were obtained and analyzed for monolayers composed from DOPC, POPC, DMPC, DPPC, DPhPC, and DMPS at the surface of solutions containing KCl, CaCl₂, or BeCl₂ and in the presence of polylysine (PLL) or chlorpromazine (CPZ). Elastic properties of monolayers are characterized by the area of lipid molecules, presented as an incompressible area with a soft shell, the size of which exponentially depends on the lateral pressure and the coefficient of elasticity. This assumption describes well the shape of the lipid compression diagrams, including lipids with saturated hydrocarbon chains (DPPC and DMPS) in the region, where they exhibit liquid crystal properties (liquid expanded state, LE). All lipids show changes in the interfacial Volta potential in this region; these changes linearly depend on the effective value of the work applied to compress the monolayer. Choosing for zero value of the Volta potential its magnitude at the point with a lateral pressure of about 1 mN/m, the slope of linear section of this dependence was estimated. The slope of this dependence makes it possible to identify different types of membrane-active compounds affecting the elastic and electrostatic characteristics of the monolayer. It turned out that this slope is practically independent of the pH and ionic composition of the aqueous subphase but decreases upon adsorption of PLL polypeptides on the surface of the DMPS monolayer. The adsorption of small positively charged CPZ molecules on this monolayer leads to the deviation in the potential vs work dependence from the linear. A quantitative description of this deviation is in a good agreement with the assumption that CPZ molecules are incorporated into the monolayer. Their contribution to the change in the energy of the monolayer and the Volta potential is determined by the amount of incorporated CPZ molecules, the effect of which on lateral pressure can be approximated by a function similar to the Boltzmann relation.

中文翻译：

---

液体膨胀状态下脂质单层压缩的边界电位和能量

摘要——

获得并分析了由 DOPC、POPC、DMPC、DPPC、DPhPC 和 DMPS 在含有 KCl、CaCl ₂或 BeCl ₂的溶液表面组成的单层的压缩图在聚赖氨酸 (PLL) 或氯丙嗪 (CPZ) 存在下。单层的弹性特性以脂质分子的面积为特征，表现为具有软壳的不可压缩区域，其大小以指数方式取决于侧压力和弹性系数。这个假设很好地描述了脂质压缩图的形状，包括在该区域具有饱和烃链（DPPC 和 DMPS）的脂质，在那里它们表现出液晶特性（液体膨胀状态，LE）。所有脂质都显示该区域的界面伏特电位发生变化；这些变化线性取决于用于压缩单层的功的有效值。选择 Volta 电位的零值，其大小在侧向压力约为 1 mN/m 的点处，估计了这种依赖性的线性部分的斜率。这种依赖性的斜率可以识别影响单层弹性和静电特性的不同类型的膜活性化合物。结果表明，该斜率实际上与含水亚相的 pH 值和离子组成无关，但在 DMPS 单层表面吸附 PLL 多肽后会降低。带正电荷的小 CPZ 分子在该单层上的吸附导致电位与功的依赖关系与线性的偏差。这种偏差的定量描述与 CPZ 分子被纳入单层的假设非常一致。