When comparing protein folding in vitro and in vivo significant differences have been found. This has been attributed to crowding and confinement effects. Using a combination of GHz- and THz-dielectric relaxation spectroscopy and MD simulations, we studied hydration dynamics and reviewed protein stability data inside sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and cetyltrimethylammonium bromide (CTAB) reverse micelles which are model systems for confinement. We find that water inside anionic AOT and cationic CTAB reverse micelles is characterized by a strong dielectric depolarization giving rise to a very low relative permittivity compared to an unconfined solution. Despite differences in the hydration dynamics of the surfactant's head groups, simulations using the two-phase thermodynamics method predict a similar reduction in water entropy for both reverse micelle systems compared to bulk water. When we compare the stability data of proteins in these reverse micelles we find that in contrast to our initial expectation, protein stability correlates rather with the local chemistry of the hydrated head groups than with the excluded volume effect or the low global permittivity.

中文翻译：

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表面活性剂头基团的局部化学决定了反胶束中蛋白质的稳定性†

当比较蛋白质折叠在体外和体内发现了显着差异。这归因于拥挤和限制作用。通过结合使用GHz和THz介电弛豫谱以及MD模拟，我们研究了水合动力学并审查了双（2-乙基己基）磺基琥珀酸钠（AOT）和十六烷基三甲基溴化铵（CTAB）反胶束中的蛋白质稳定性数据，该胶束是用于禁闭。我们发现，阴离子AOT和阳离子CTAB反胶束中的水的特征在于强电介质去极化，与无侧限溶液相比，其介电常数非常低。尽管表面活性剂头基的水合动力学存在差异，使用两相热力学方法进行的模拟预测，与散装水相比，两个反胶束系统的水熵都有相似的降低。当我们比较这些反胶束中蛋白质的稳定性数据时，我们发现与我们最初的预期相反，蛋白质稳定性与水合头基的局部化学性质相关，而与排除体积效应或低整体介电常数相关。