Departamento de Química Biológica, Centro de Investigaciones en Química Biológica de Córdoba (CIQUIBIC), Facultad de Ciencias Químicas, CONICET, Universidad Nacional de Córdoba, Haya de la Torre y Medina Allende, Ciudad Universitaria, X5000HUA, Córdoba, Argentina. lfanani@ fcq.unc.edu.ar
J Phys Chem B. 2011 Jan 13;115(1):41-9. doi: 10.1021/jp107344t. Epub 2010 Dec 10.
This work describes how changes in surface pressure modulate the molecular organization of Langmuir monolayers formed by ternary mixtures of dlPC/pSM/Dchol that exhibit coexistence of liquid-expanded (LE) and liquid-ordered (Lo) phases. It provides a theoretical framework for understanding the pressure-induced critical miscibility point characteristic of monolayer systems with liquid-liquid phase coexistence. From compression isotherms and Brewster angle microscopy of Langmuir monolayers with a composition close to a tie line, we determined experimental values of mean molecular areas, surface potential, and monolayer thickness and could estimate the mean molecular area and composition of each coexisting phase. A surface-pressure-induced enrichment of the PC component in the Lo phase reduces both the compositional miscibility gap and the hydrophobic mismatch between phases. The liquid-liquid miscibility transition point observed at ≈25 mN/m can be explained by a competition between thermal energy and the line tension arising from the hydrophobic mismatch between the coexisting liquid phases.
这项工作描述了表面压力的变化如何调节 dlPC/pSM/Dchol 三元混合物形成的 Langmuir 单层的分子组织，这些混合物表现出液体膨胀（LE）和液体有序（Lo）相的共存。它为理解具有液-液相共存的单层系统中压力诱导的临界混溶性点提供了一个理论框架。从接近 tie line 的 Langmuir 单层的压缩等温线和布鲁斯特角显微镜，我们确定了平均分子面积、表面电势和单层厚度的实验值，并可以估计每个共存相的平均分子面积和组成。表面压力诱导的 Lo 相中 PC 成分的富集降低了相间的组成混溶性间隙和疏水性不匹配。在 ≈25 mN/m 观察到的液-液混溶性转变点可以通过共存液体相之间的热能量和线张力之间的竞争来解释，这种线张力源于疏水性不匹配。
