各向异性带电球体间电荷调控静电相互作用的闭式理论
A closed-form theory of charge-regulated electrostatic interactions between anisotropically charged spheres
- Department of Theoretical Physics, Jožef Stefan Institute（约瑟夫·斯蒂芬研究所理论物理系）
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AI总结：
本研究提出融合电荷调控与斑状特性的闭式理论，推导各向异性带电球体的相互作用能，应用于两种蛋白质时可复现实验数据并预测吸引态条件的扩展。
AI中文摘要：
蛋白质及诸多胶体带有可电离表面基团，这些基团兼具空间非均匀性（呈斑状）与pH响应性（电荷调控特性）。在描述此类粒子间静电相互作用时，这两个特性常被分开处理，尤其在理论研究中。我们提出一种统一的闭式理论，在线性化泊松-玻尔兹曼近似框架内融合电荷调控与斑状特性。对于带有可滴定位点各向异性分布的球形粒子，我们推导了领头阶平均场相互作用能以及Kirkwood-Shumaker涨落相互作用。该理论揭示了两个电中性各向异性粒子间的一种全新定性效应：邻近诱导的电荷调控会产生净单极子，并分裂出在任何线性固定电荷模型中简并的取向分支。伴随的相互作用能修正无固定符号——它会弱化同电荷排斥作用，但在等电点外可加深或产生吸引作用。我们将该理论的三个组成部分与已发表结果进行基准测试；现有模拟未涉及它们的组合，而该组合可捕捉理论的核心预测。最后，我们将该理论应用于溶菌酶和α-胰凝乳蛋白酶原A两种蛋白质，结果显示它不仅能合理复现测得的第二维里系数，还能预测电荷调控如何扩大蛋白质-蛋白质相互作用呈吸引态的pH范围与屏蔽强度范围。
英文摘要：
Proteins and many other colloids carry ionizable surface groups that are both spatially inhomogeneous (patchy) and pH-responsive (charge-regulating). In the description of the electrostatic interactions between such particles, these two aspects are often treated separately, especially from a theoretical perspective. We present a unified, closed-form theory that unites charge regulation and patchiness within the linearized Poisson--Boltzmann approximation. For spherical particles with anisotropic distributions of titratable sites, we derive both the leading-order mean-field interaction energy as well as the Kirkwood--Shumaker fluctuation interaction. The theory exposes a qualitatively new effect between two electroneutral anisotropic particles: proximity-induced charge regulation generates a net monopole, and splits orientational branches that are degenerate in any linear fixed-charge model. The accompanying correction to the interaction energy has no fixed sign---it softens like-charge repulsion but can deepen or create attraction away from the isoelectric point. We benchmark three ingredients of the theory against published results; no existing simulation probes their combination, which would capture the central prediction of the theory. Lastly, we apply the theory to two proteins---lysozyme and $α$-chymotrypsinogen A---and show that it not only reproduces the measured second virial coefficients reasonably well but also predicts how charge regulation expands the range of pH and screening strength where the protein--protein interaction is attractive.
