Stenstam Anna, Khan Ali, Wennerström Håkan
Physical Chemistry 1, Lund University, P.O. Box 124, SE-222 21 Lund, Sweden.
Langmuir. 2004 Aug 31;20(18):7760-5. doi: 10.1021/la049508w.
We investigate the competition between the associations of oppositely charged protein-surfactant complexes and oppositely charged surfactant complexes. In all systems examined, the most favorable complexation is the one between the two oppositely charged surfactant ions, despite the strong binding known, for example, dodecyl sulfate, DS-, to lysozyme. Thus, the phase behavior of the catanionic system is dominating the features observed also in the presence of protein. The phase behavior of the dilute protein-free dodecyltrimethylammonium chloride-sodium dodecyl sulfate-water system is presented and used as a basis for the discussion on the different solubilization mechanisms. Our results show that the mechanism for resolubilization of a protein-surfactant salt is fundamentally different when it is caused by addition of a second surfactant than when it is accomplished by an excess of the first surfactant. The competition between lysozyme and cationic amphiphiles as hosts for the anionic surfactants was studied experimentally and analyzed quantitatively. Aggregates with C12 cationic surfactants are clearly preferred by the anionic surfactants, while for C10 and particularly C8 a clear excess of cationic surfactant has to be added to completely dissolve the complex salt lysozyme-anionic surfactant.
我们研究了带相反电荷的蛋白质 - 表面活性剂复合物与带相反电荷的表面活性剂复合物之间的竞争关系。在所有研究的体系中，最有利的络合作用发生在两种带相反电荷的表面活性剂离子之间，尽管例如十二烷基硫酸盐（DS⁻）与溶菌酶之间存在强结合作用。因此，阴阳离子体系的相行为主导了在蛋白质存在时所观察到的特征。本文给出了稀的不含蛋白质的十二烷基三甲基氯化铵 - 十二烷基硫酸钠 - 水体系的相行为，并以此为基础讨论了不同的增溶机制。我们的结果表明，当通过添加第二种表面活性剂导致蛋白质 - 表面活性剂盐再溶解时，其机制与通过过量的第一种表面活性剂实现再溶解时的机制有根本的不同。实验研究并定量分析了溶菌酶与作为阴离子表面活性剂宿主的阳离子两亲物之间的竞争关系。阴离子表面活性剂明显更倾向于与含有C12阳离子表面活性剂的聚集体结合，而对于C10尤其是C8，必须添加明显过量的阳离子表面活性剂才能完全溶解溶菌酶 - 阴离子表面活性剂复合盐。
