pH值及离子浓度对DDAO与DNA作用后凝聚形态的影响

To explore the interaction between DDAO and DNA using single molecule technology

用单分子技术来探究十二烷基二甲基氧化铵(DDAO)和DNA相互作用过程,可揭示其相互作用机制,且为获得安全高效的转基因非病毒载体提供理论参考。本文主要通过原子力显微镜(AFM)、磁镊(MT)技术来探究pH值及单价离子浓度(NaCl)的改变对DDAO与DNA作用后的凝聚形态和临界凝聚力的影响。实验结果显示随着溶液pH值由7.0降低到4.0,DDAO-DNA复合物的形态由自由松散状态变为紧密的网格及花状结构,复合物的临界凝聚力由0 pN升高到3.9 pN左右,说明DNA凝聚的发生;接着在混合溶液中(pH=5.5)加入不同浓度的NaCl时,复合物的形态从网格及花状结构又变为松散的状态,临界凝聚力也逐渐减小到0。可见DDAO在酸性条件下对DNA具有凝聚作用且随溶液pH降低而增强,而单价离子浓度对DNA的凝聚有抑制作用并且也随着浓度的增加而增强。

The study of the interaction between dodecyldimethylamine oxide(DDAO)and DNA using single molecular technique can reveal the interaction mechanism and provide a theoretical reference for obtaining safe and efficient transgenic non-viral vectors.In this paper,atomic force microscope(AFM)and magnetic tweezers(MT)were used to explore the influence of pH value and concentration of monovalent ions(NaCl)on the condensation morphology and critical condensing force of DDAO and DNA.The experimental results showed that as the pH value of the solution decreased from 7.0 to 4.0,the morphology of the DDAO-DNA complex changed from free and loose state to tight network and flower-like structure,and the critical condensing force of the complex increased from 0 pN to about 3.9 pN,indicating the occurrence of DNA condensation.Then,when different concentrations of NaCl were added to the mixed solution(pH=5.5),the morphology of the complex changed from condensed flower-like structure to loose state,and the critical condensing force gradually decreased to 0.It can be seen that DDAO has a condensation effect on DNA under acidic conditions.The effect increases with the decrease of pH value of the solution.The concentration of monovalent ions has an inhibition effect on the condensation of DNA and the effect increases with the increase of concentration.