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Abstract：
GdmCl and NaSCN are two strong chaotropic salts commonly used in protein folding and stability studies, but their microscopic mechanisms remain enigmatic. Here, by CD and NMR, we investigated their effects on conformations, stability, binding and backbone dynamics on ps-ns and µs-ms time scales of a 39-residue but well-folded WW4 domain at salt concentrations ≤200 mM. Up to 200 mM, both denaturants did not alter the tertiary packing of WW4, but GdmCl exerted more severe destabilization than NaSCN. Intriguingly, GdmCl had only weak binding to amide protons, while NaSCN showed extensive binding to both hydrophobic side chains and amide protons. Neither denaturant significantly affected the overall ps-ns backbone dynamics, but they distinctively altered µs-ms backbone dynamics. This study unveils that GdmCl and NaSCN destabilize a protein before the global unfolding occurs with differential binding properties and µs-ms backbone dynamics, implying the absence of a simple correlation between thermodynamic stability and backbone dynamics of WW4 at both ps-ns and µs-ms time scales.
摘要：
GdmCl和NaSCN是蛋白质折叠和稳定性研究中常用的两种强离液盐，但它们的微观机制仍然神秘。这里,通过CD和NMR，我们研究了它们对构象的影响，稳定性,在盐浓度≤200mM的39个残基但折叠良好的WH4域的ps-ns和µs-ms时间尺度上的结合和主链动力学。高达200mM，两种变性剂均未改变WW4的三级填料，但GdmCl比NaSCN产生更严重的不稳定作用。有趣的是，GdmCl仅与酰胺质子弱结合，而NaSCN显示与疏水性侧链和酰胺质子的广泛结合。两种变性剂都不会显着影响整个ps-ns骨架动力学，但它们明显改变了µs-ms骨干动力学。这项研究揭示了GdmCl和NaSCN在全局解折叠发生之前使蛋白质不稳定，具有不同的结合特性和µs-ms主链动力学，这意味着在ps-ns和µs-ms时间尺度上，WW4的热力学稳定性和骨架动力学之间不存在简单的相关性。
