Interface Counterion Localization Induces a Switch between Tight and Loose Configurations of Knotted Weak Polyacid Rings despite Intermonomer Coulomb Repulsions,The Journal of Physical Chemistry B

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Interface Counterion Localization Induces a Switch between Tight and Loose Configurations of Knotted Weak Polyacid Rings despite Intermonomer Coulomb Repulsions
The Journal of Physical Chemistry B ( IF 2.8 ) Pub Date : 2020-03-26 , DOI: 10.1021/acs.jpcb.0c00620
Andrea Tagliabue ₁ , Lorella Izzo ₂ , Massimo Mella ₁

Affiliation

Stochastic simulations have been used to investigate the conformational behavior of knotted weak polyacid rings as a function of pH. Different from the commonly expected ionization–repulsion–expansion scheme upon increasing pH, theoretical results suggest a nonmonotonic behavior of the gyration radius R_g². Polyelectrolyte recontraction at high ionization is induced by the weakening of Coulomb repulsion due to counterions (CIs) localizing at the interphase between the polymer and solvent, and the more marked it appears, the more complex is the knot topology. Compared with strong polyelectrolytic species of identical ionization, weak polyacids present tighter knots due to their ability to localize neutral monomers inside the tangled part. Increasing the solvent Bjerrum length enhances CIs localization, lowering the pH at which polyacids start decreasing their average size. A similar effect is also obtained by increasing the amount of “localizable” cations by adding salts.

中文翻译：

尽管有单体间库仑排斥作用，但界面抗衡离子局部化仍可在打结的弱多元酸环的紧密构型和松散构型之间切换。

随机模拟已用于研究打结的弱多元酸环的构象行为随pH的变化。与通常期望的在增加pH值下的电离-排斥-扩展方案不同，理论结果表明，回转半径R _g²具有非单调性。高电离作用下的聚电解质再收缩是由于抗衡离子（CIs）位于聚合物和溶剂之间的相间而导致的库仑排斥力减弱而引起的，并且它出现的越明显，结形拓扑就越复杂。与具有相同电离作用的强聚电解物质相比，弱聚酸由于其在缠结部分内定位中性单体的能力而呈现出更紧密的结。增加溶剂Bjerrum的长度会增强CI的定位，从而降低多酸开始减小其平均粒径的pH。通过添加盐增加“可定位”阳离子的量，也可以获得类似的效果。

更新日期：2020-03-27

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