Membrane fouling continues to hamper the performance of membrane-filtration processes. A challenge with macromolecular foulants like proteins is that macroscopic characterizations, like net electrical charge, may be poorly correlated with membrane fouling. This necessitates a molecular-scale analysis of the local interactions. In this study, molecular dynamics simulations have been performed to understand the interactions between two similar-sized proteins with opposite overall charges (namely, lysozyme and α-lactalbumin) and a negative-charged membrane. Surprisingly, the protein–membrane distances and adsorption probabilities of both proteins are similar. Compared with the positive-charged lysozyme, the negative-charged α-lactalbumin exhibits (a) greater protein–membrane attractive interaction energy due to synergy among adsorption sites; (b) lower root-mean-squared deviations (RMSD); and (c) greater number of residues that show low root-mean-squared fluctuations (RMSF). These results indicate that local interactions are critical and thus highlight the pitfall of using the overall protein characteristics as predictors of membrane fouling.

中文翻译：

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带相反电荷蛋白质对膜污染的分子动力学研究

膜污染继续阻碍膜过滤过程的性能。像蛋白质这样的大分子污染物的一个挑战是宏观特征，如净电荷，可能与膜污染的相关性很差。这需要对局部相互作用进行分子级分析。在这项研究中，已经进行了分子动力学模拟，以了解两种具有相反总电荷（即溶菌酶和 α-乳清蛋白）和带负电荷的膜的大小相似的蛋白质之间的相互作用。令人惊讶的是，两种蛋白质的蛋白质-膜距离和吸附概率相似。与带正电的溶菌酶相比，带负电的 α-乳清蛋白表现出（a）由于吸附位点之间的协同作用，具有更大的蛋白质-膜吸引力相互作用能；(b) 较低的均方根偏差 (RMSD)；(c) 显示低均方根波动 (RMSF) 的更多残基。这些结果表明局部相互作用是至关重要的，因此突出了使用整体蛋白质特征作为膜污染预测因子的陷阱。