Fernández Marta Cejudo, Sánchez Cecilio Carrera, Rodríguez Niño Maria Rosario, Rodríguez Patino Juan M
Departamento de Ingeniería Química, Facultad de Química, Universidad de Sevilla, C/. Prof. García González 1, 41012-Seville, Spain.
Langmuir. 2007 Jun 19;23(13):7178-88. doi: 10.1021/la7003497. Epub 2007 May 19.
In this work we have analyzed the structural, topographical, and shear characteristics of mixed monolayers formed by adsorbed beta-lactoglobulin (beta-lg) and spread monoglyceride (monopalmitin or monoolein) on a previously adsorbed protein film. Measurements of the surface pressure (pi)-area (A) isotherm, Brewster angle microscopy (BAM), and surface shear characteristics were obtained at 20 degrees C and at pH 7 in a modified Wilhelmy-type film balance. The pi-A isotherm and BAM images deduced for adsorbed beta-lactoglobulin-monoglyceride mixed films at pi lower than the equilibrium surface pressure of beta-lactoglobulin (pi(e)(beta-lg)) indicate that beta-lactoglobulin and monoglyceride coexist at the interface. However, the interactions between protein and monoglyceride are somewhat weak. At higher surface pressures (at pi > or = pi(e)(beta-lg)) a protein displacement by the monoglyceride from the interface takes place. The surface shear viscosity (eta(s)) of mixed films is very sensitive to protein-monoglyceride interactions and displacement as a function of monolayer composition (protein/monoglyceride fraction) and surface pressure. Shear can induce change in the morphology of monoglyceride and beta-lactoglobulin domains, on the one hand, and segregation between domains of the film-forming components on the other hand. In addition, the displacement of beta-lactoglobulin by the monoglycerides is facilitated under shear conditions.
在本研究中，我们分析了由吸附的β-乳球蛋白（β-lg）和铺展的甘油单酯（单棕榈酸甘油酯或单油酸甘油酯）在先前吸附的蛋白质膜上形成的混合单层的结构、形貌和剪切特性。在改良的Wilhelmy型膜天平中，于20℃和pH 7条件下获得了表面压力（π）-面积（A）等温线、布鲁斯特角显微镜（BAM）图像以及表面剪切特性。对于吸附的β-乳球蛋白-甘油单酯混合膜，在π低于β-乳球蛋白的平衡表面压力（πe(β-lg)）时推导出的π-A等温线和BAM图像表明，β-乳球蛋白和甘油单酯在界面处共存。然而，蛋白质与甘油单酯之间的相互作用有些微弱。在较高表面压力下（π≥πe(β-lg)），甘油单酯会将蛋白质从界面处置换出来。混合膜的表面剪切粘度（ηs）对蛋白质-甘油单酯相互作用以及置换非常敏感，它是单层组成（蛋白质/甘油单酯比例）和表面压力的函数。一方面，剪切可诱导甘油单酯和β-乳球蛋白域的形态发生变化，另一方面，可导致成膜组分域之间的分离。此外，在剪切条件下，甘油单酯对β-乳球蛋白的置换更容易发生。
