Langmuir. 2022 Jun 21;38(24):7413-7421. doi: 10.1021/acs.langmuir.2c00206. Epub 2022 Jun 7.
Aside from its prominent role in the excretory system, urea is also a known protein denaturant. Here, we characterize urea as it behaves in confined spaces of AOT (sodium bis(2-ethylhexyl) sulfosuccinate) reverse micelles as a model of tight, confined spaces found at the subcellular level. Dynamic light scattering revealed that low temperatures (275 K) caused the smallest of the reverse micelle sizes, = 10, to destabilize and dramatically increase in apparent hydrodynamic diameter. We attribute this to urea embedded into the surfactant interface as confirmed by 2D H-NOESY NMR spectroscopy. This increase in size in turn caused the hydrogen exchange between urea and water within the nanosized reverse micelles to increase as measured by 1D EXSY-NMR. A minimal enlarging effect and no increase in hydrogen exchange were observed when aqueous urea was introduced into = 15 or 20 reverse micelles, suggesting that this effect is unique to particularly small-diameter spaces (∼7 nm).
除了在排泄系统中发挥重要作用外，尿素还是一种已知的蛋白质变性剂。在这里，我们将尿素描述为在 AOT（琥珀酸双（2-乙基己基）酯磺酸钠）反胶束的封闭空间中的行为，AOT 反胶束是亚细胞水平上发现的紧密、封闭空间的模型。动态光散射显示，低温（275 K）会导致最小的反胶束尺寸， = 10，变得不稳定，并在表观水动力直径上急剧增加。我们将其归因于尿素嵌入到表面活性剂界面中，这一点得到了二维 H-NOESY NMR 光谱的证实。这种尺寸的增加反过来又导致 1D EXSY-NMR 测量的尿素与纳米级反胶束内水之间的氢交换增加。当将水合尿素引入到 = 15 或 20 的反胶束中时，仅观察到最小的放大效应和氢交换没有增加，这表明这种效应是特别小直径空间（∼7nm）所独有的。
