Weak polyelectrolyte brushes are a promising platform for the selective capture and release of charged proteins from bulk solutions. Despite their potential for creating smart responsive surfaces, a detailed microscopic understanding of the uptake behavior in dependence of various parameters remains elusive. In this study, we employ coarse-grained, particle-based simulations to investigate how charge regulation under varying environmental conditions modulate the uptake and release of pH-responsive ampholytes, serving as a toy model for proteins, into weak polyelectrolyte brushes. For quenched brushes with constant ionization, the uptake of ampholytes remains strong across different isoelectric points. In contrast, for weak brushes, the ampholyte uptake becomes selectively sensitive to different isoelectric points and pK_A-values and exhibits a nonmonotonic behavior with changing pH. Enhanced proton partitioning into the brush lowers the local pH, significantly shifting the ionization states of both the brush (pK_A^app > pK_A) and ampholytes (pI^app > pI), such that the concurrent ionization of the brush and the ampholyte results in an optimum uptake strength for pK_A^app < pH < pI^app. Adjusting the salt concentration broadens the uptake window and shifts the maximum uptake to higher pH values. Additionally, ampholytes with higher charge regulation capacitance near the isoelectric point demonstrate stronger adsorption, extending selective adsorption capabilities in ampholyte mixtures with similar isoelectric points.

中文翻译：

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电荷调节如何影响弱聚电解质刷中 pH 响应性两性电解质的摄取


弱聚电解质刷是从本体溶液中选择性捕获和释放带电蛋白质的有前途的平台。尽管它们有可能创建智能响应表面，但对依赖于各种参数的摄取行为的详细微观理解仍然难以捉摸。在这项研究中，我们采用粗粒、基于颗粒的模拟来研究不同环境条件下的电荷调节如何调节 pH 响应性两性电解质的吸收和释放，作为蛋白质的玩具模型，进入弱聚电解质刷。对于具有恒定电离的淬火刷，两性电解体在不同等电点上的吸收仍然很强。相反，对于弱刷子，两性电解质吸收对不同的等电点和 pK_A 值变得选择性敏感，并且随着 pH 值的变化而表现出非单调行为。增强的质子分配到刷子中降低了局部 pH 值，显着改变了刷子（pK_A^app >p K_A）和两性离子体（pI^app > pI）的电离状态，因此电刷和两性离子物的同步电离导致 pK_A^应用程序 < pH < pI^应用程序的最佳摄取强度.调整盐浓度会拓宽吸收窗口，并将最大吸收转移到更高的 pH 值。此外，在等电点附近具有较高电荷调节电容的两性电解质表现出更强的吸附能力，从而扩展了在具有相似等电点的两性电解质混合物中的选择性吸附能力。