Joos Paul, Tomoaia-Cotisel Andrada, Sellers Andrew J, Tomoaia-Cotisel Maria
Department of Chemistry, University of Antwerp, B-2610 Wilrijk, Belgium.
Colloids Surf B Biointerfaces. 2004 Sep 1;37(3-4):83-91. doi: 10.1016/j.colsurfb.2004.03.019.
The kinetic analysis of the adsorption of two carotenoids (i.e., ethyl ester of beta-apo-8'-carotenoic acid and beta-carotene, all trans-isomers) from n-hexane solutions at the oil/water interface is presented for several carotenoid concentrations in the oil phase. A new kinetic approach is developed and it addresses the diffusion adsorption associated with a reversible interfacial reaction, which describes the reorientation of surfactant molecules between two conformations. This approach leads to a general analytical expression that contains four physical parameters and describes with high accuracy the experimental dynamic interfacial tensions for the two carotenoids, which independently adsorb from n-hexane phase to the n-hexane/water interface. The calculations give the characteristic times for the carotenoid adsorption at the oil/water interface in terms of diffusion relaxation and kinetic relaxation times. The results explain the long time effects on the adsorption of these carotenoids at the oil/water interface. The data are in substantial agreement with the molecular structure of these carotenoids and with the earlier data recorded for cholesterol adsorption at the n-heptane/water interface. Based on these findings, we propose a molecular mechanism for the interfacial transformation of carotenoid molecules at a hydrophobic/hydrophilic interface.
本文针对油相中几种类胡萝卜素浓度，给出了两种类胡萝卜素（即β-阿朴-8'-胡萝卜酸乙酯和β-胡萝卜素，均为全反式异构体）从正己烷溶液在油/水界面吸附的动力学分析。开发了一种新的动力学方法，该方法处理与可逆界面反应相关的扩散吸附，此反应描述了表面活性剂分子在两种构象之间的重新取向。这种方法得到了一个包含四个物理参数的通用解析表达式，该表达式能高精度地描述这两种类胡萝卜素（它们从正己烷相独立吸附到正己烷/水界面）的实验动态界面张力。计算给出了类胡萝卜素在油/水界面吸附的特征时间，以扩散弛豫时间和动力学弛豫时间表示。结果解释了这些类胡萝卜素在油/水界面吸附的长时间效应。数据与这些类胡萝卜素的分子结构以及之前记录的胆固醇在正庚烷/水界面吸附的数据基本一致。基于这些发现，我们提出了类胡萝卜素分子在疏水/亲水界面进行界面转变的分子机制。
