St. Petersburg National Research University of Information Technologies, Mechanics and Optics, St. Petersburg 197101, Russia.
Institute of Macromolecular Compounds of the Russian Academy of Sciences, St. Petersburg 199004, Russia.
Langmuir. 2021 Mar 9;37(9):2865-2873. doi: 10.1021/acs.langmuir.0c02837. Epub 2021 Feb 24.
Weak polyampholytes and globular proteins among them can be efficiently absorbed from solutions by polyelectrolyte brushes or microgels even if the net charge of the polyampholyte is of the same sign as that of the brush/microgel. We use a mean-field approach for calculating the free energy of insertion of a probe polyampholyte molecule into a polyelectrolyte brush/microgel. We anticipate that the insertion of the polyampholyte into similarly charged brush/microgel may be thermodynamically favorable due to the gain in the cumulative re-ionization free energy of the pH-sensitive acidic and basic residues. Importantly, we demonstrate that the polyampholyte (protein) charge sign inversion upon transfer from the bulk of the solution to the brush/microgel does not provide sufficient conditions to assure negative re-ionization free energy balance. Thus (in the absence of other driving or stopping mechanisms), charge sign inversion does not necessarily provoke spontaneous absorption of the polyampholyte into the brush/microgel.
即使聚两性电解质的净电荷与刷/微凝胶的电荷相同，弱聚两性电解质和其中的球状蛋白质也可以通过聚电解质刷或微凝胶从溶液中有效地被吸收。我们使用平均场方法来计算探针聚两性电解质分子插入聚电解质刷/微凝胶的自由能。我们预计，由于 pH 敏感的酸性和碱性残基的累积再电离自由能的增加，聚两性电解质插入带相同电荷的刷/微凝胶可能在热力学上是有利的。重要的是，我们证明了聚两性电解质（蛋白质）在从溶液主体转移到刷/微凝胶时电荷符号的反转并不能提供确保负再电离自由能平衡的充分条件。因此（在没有其他驱动或停止机制的情况下），电荷符号的反转不一定会促使聚两性电解质自发地被吸收到刷/微凝胶中。
