Lipid phase behaviour under steady state conditions
Lipid phase behaviour under steady state conditions
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DOI：
10.1039/c2fd20079a
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发表时间：
2013-01-01
影响因子：
3.4
通讯作者：
Wennerstrom, Hakan
中科院分区：
文献类型：
--
作者：
Aberg, Christoffer;Sparr, Emma;Wennerstrom, Hakan
在两个区域之间的界面处，例如脂质溶液的空气-液体界面，可能出现非平衡情况。通常，对应于环境RH的水化学势与溶液的水化学势不匹配，并且化学势的梯度引起扩散流。如果本体水化学势接近相变，则有可能形成具有与本体中发现的结构在性质上不同的结构的界面相。基于对二组分体系中这一现象的分析（C. Aberg，E. Sparr，K. Edler和H. Wennerstrom，Langmuir，2009，25，12177），我们在这里分析三组分系统的现象。导出了相应的输运方程，并给出了某些极限情况下的显式结果。然后将形式主义概念性地应用于四种不同的水性脂质系统，其除了水和磷脂之外还含有（i）辛基葡糖苷，（ii）脲，（iii）重水，和（iv）胆酸钠作为第三组分。选择这四种情况来说明（i）使用胶束形成剂将脂质输送到可形成多层结构的界面的方法;（ii）使用共溶剂抑制在界面处形成凝胶相;（iii）在界面处形成纯磷脂多层结构的方法;（iv）在界面区域中形成相序列的方法。这四种情况都具有理论基础的性质，其条件在实践中能否实现还有待于实验研究。
At the interface between two regions, for example the air-liquid interface of a lipid solution, there can arise non-equilibrium situations. The water chemical potential corresponding to the ambient RH will, in general, not match the water chemical potential of the solution, and the gradients in chemical potential cause diffusional flows. If the bulk water chemical potential is close to a phase transition, there is the possibility of forming an interfacial phase with structures qualitatively different from those found in the bulk. Based on a previous analysis of this phenomenon in two component systems (C. Aberg, E. Sparr, K. J. Edler and H. Wennerstrom, Langmuir, 2009, 25, 12177), we here analyse the phenomenon for three-component systems. The relevant transport equations are derived, and explicit results are given for some limiting cases. Then the formalism is applied conceptually to four different aqueous lipid systems, which in addition to water and a phospholipid contain (i) octyl glucoside, (ii) urea, (iii) heavy water, and (iv) sodium cholate as the third component. These four cases are chosen to illustrate (i) a method to use a micelle former to transport lipid to the interface where a multi-lamellar structure can form; (ii) to use a co-solvent to inhibit the formation of a gel phase at the interface; (iii) a method to form pure phospholipid multi-lamellar structures at the interface; (iv) a method to form a sequence of phases in the interfacial region. These four cases all have the character of theoretically based conjectures and it remains to investigate experimentally whether or not the conditions can be realized in practice.