Impact of Urea on Detergent Micelle Properties
Impact of Urea on Detergent Micelle Properties
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DOI：
10.1021/la4013747
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发表时间：
2013-07-09
期刊：
影响因子：
3.9
通讯作者：
Keller, Sandro
中科院分区：
文献类型：
--
作者：
Broecker, Jana;Keller, Sandro
助溶剂，如尿素，可以引起洗涤剂胶束化行为的剧烈变化。我们提出了一个系统的量化尿素的临界胶束浓度的影响，胶束化热力学，和胶束尺寸在三个同源系列的常用的非离子烷基洗涤剂。为此，我们进行了脱胶束实验，通过等温滴定量热法和动态光散射的烷基maltopyranosides，环己基烷基maltopyranosides，和烷基glucopyranosides，环己基烷基maltopyranosides，和烷基glucopyranosides在尿素浓度为0-8 M的流体动力学尺寸测量。对于所有洗涤剂的研究，我们发现，临界胶束浓度呈指数增加，因为胶束化的绝对吉布斯自由能在整个尿素浓度范围内线性下降，胶束尺寸。与此相反，胶束化的热力学和熵的贡献揭示了更复杂的，非线性依赖于尿素浓度。自由能和尺寸变化对于长链洗涤剂更明显，其在胶束形成时掩埋更多的非极性表面积。每个洗涤剂系列内的每个亚甲基基团的吉布斯自由能增量以线性方式取决于尿素浓度，尽管它们是由烷基麦芽糖苷的熵项引起的，但对于环己基烷基麦芽糖苷来说，它们是衍生的。我们比较我们的研究结果转移自由能的氨基酸侧链，将它们与蛋白质折叠的数据，并讨论如何尿素诱导的洗涤剂胶束性质的变化影响在体外膜蛋白的调查。
Co-solvents, such as urea, can entail drastic changes in the micellization behavior of detergents. We present a systematic quantification of the impact of urea on the critical micellar concentration, the micellization thermodynamics, and the micelle size in three homologous series of commonly used non-ionic alkyl detergents. To this end, we performed demicellization experiments by isothermal titration calorimetry and hydrodynamic size measurements by dynamic light scattering on alkyl maltopyranosides, cyclohexyl alkyl maltopyranosides, and alkyl glucopyranosides, cyclohexyl alkyl maltopyranosides, and alkyl glucopyranosides at urea concentrations of 0-8 M. For all detergents studied, we found that the critical micellar concentration increases exponentially because the absolute Gibbs free energy of micellization decreases linearly over the entire urea concentration range, as does the micelle size. In contrast, the enthalpic and entropic contributions to micellization reveal more complex, nonlinear dependences on urea concentration. Both free energy and size changes are more pronounced for long-chain detergents, which bury more apolar surface area upon micelle formation. The Gibbs free energy increments per methylene group within each detergent series depend on urea concentration in a linear fashion, although they result from the entropic term for alkyl maltosides but are of enthalpic origin for cyclohexyl alkyl maltosides. We compare our results to transfer free energies of amino acid side chains, relate them to protein-folding data, and discuss how urea-induced changes in detergent micelle properties affect in vitro investigations on membrane proteins.