不同价态的阴离子在DNA凝聚效应中的抑制作用

为了定量地研究阴离子对DNA凝聚和电荷中和过程的抑制作用，利用动态光散射和原子力显微镜研究了不同价态阴离子对阳离子介导的DNA凝聚效应的影响。在动态光散射实验中，阴离子可以使阳离子作用后的DNA的电泳迁移率变小，即对DNA的电荷中和有抑制作用，而且阴离子价态越高，对电泳迁移率的抑制作用越强。改变阳离子种类但控制相同的阳离子浓度，发现阴离子对DNA的电荷中和有同样的抑制作用及趋势，同时用原子力显微镜观察DNA的凝聚形态变化也得出一致的结果。在相同阳离子浓度下，高价阴离子相对低价态阴离子，对DNA凝聚的抑制作用更强，使DNA的凝聚形态变得更加松散，进一步证实了阴离子对阳离子导致的DNA凝聚有减弱作用。

Inhibition of DNA condensation by anions of various valencies

To quantitatively study the inhibitory effect of anions on DNA condensation and charge neutralization, the effect of anions of various valencies on cation-mediated DNA condensation was studied using dynamic light scattering and atomic force microscopy (ATM). Dynamic light scattering experiments showed that anions reduced the electrophoretic mobility of DNA in the presence of cations, indicating that charge neutralization of DNA was inhibited. The higher valence of anions, the stronger was the inhibition of electrophoretic mobility. Different anions exerted the same inhibitory effect and trend on DNA charge neutralization at the same concentration of various cations. Meanwhile, the morphological changes in DNA condensation as observed by AFM led to the same conclusion. At the same cation concentration, high valent cations showed more potent inhibition on DNA condensation than low valent cations, which make the DNA aggregation morphology more loose. These observations further confirmed that anions have a weakening effect on cation mediated DNA condensation.