Although electrostatics have long been recognized to play an important role in hydrogen exchange (HX) with solvent, the quantitative assessment of its magnitude in the unfolded state has hitherto been lacking. This limits the utility of HX as a quantitative method to study protein stability, folding, and dynamics. Using the intrinsically disordered human protein α-synuclein as a proxy for the unfolded state, we show that a hybrid mean-field approach can effectively compute the electrostatic potential at all backbone amide positions along the chain. From the electrochemical potential, a fourfold reduction in hydroxide concentration near the protein backbone is predicted for the C-terminal domain, a prognosis that is in direct agreement with experimentally derived protection factors from NMR spectroscopy. Thus, impeded HX for the C-terminal region of α-synuclein is not the result of intramolecular hydrogen bonding and/or structure formation.

尽管长期以来人们一直认为静电在与溶剂的氢交换 (HX) 中发挥重要作用，但迄今为止一直缺乏对其在展开状态下的量级的定量评估。这限制了 HX 作为研究蛋白质稳定性、折叠和动力学的定量方法的效用。使用本质上无序的人类蛋白质α-突触核蛋白作为未折叠状态的代表，我们表明混合平均场方法可以有效地计算链上所有骨架酰胺位置的静电势。从电化学电位来看，预测蛋白质骨架附近的氢氧化物浓度在 C 端结构域会降低四倍，这一预测与 NMR 光谱实验得出的保护因子直接一致。因此， α-突触核蛋白C 末端区域的 HX 受阻不是分子内氢键和/或结构形成的结果。