不同pH环境下二价离子对聚电解质链的影响

基于郎之万动力学方法，研究了不同pH环境下二价反离子对半柔性聚电解质链构象变化的影响。聚电解质用粗粒度的珠簧模型表示，在pH-pK>0时，回转半径几乎不变，随着pH-pK值的降低，聚电解质链的回转半径减小并且逐渐发生了缩合。在实验中，通过改变Mg2+介导下DNA溶液的pH环境，对DNA进行了原子力显微镜扫描成像，发现DNA在中性和弱酸性环境中保持自由松散状态，当pH降低到4以下，即酸性变强时DNA逐步缩合成球状并达到稳定，这一结果与模拟结果一致。

Effect of divalent ions on the polyelectrolyte chains at different pH

In this study, the effect of divalent counterions on the conformational change of the semi-flexible polyelectrolyte chains was investigated at different pH based on Langevin’s dynamics. Polyelectrolyte is represented by a coarse-grained bead spring model, with the radius of gyration (Rg) remaining almost constant at pH-pK>0. Rg reduces and the polyelectrolyte chain shrinks as the value of pH-pK decreases. Meanwhile, in the experiment, the atomic force microscopy images of the DNA mediated by Mg²⁺ were obtained in different pH environments to denote that the DNA remained in a free and loose state in neutral and weakly acidic environments. At pH<4, i.e., strong acidity, DNA was gradually condensed into a spherical shape and stabilized. Further, the experimental result agrees with the simulation results.