介电环境对DNA电泳迁移率及凝聚构象的影响

The effect of dielectic environment on DNA electrophoretic mobility and condensed conformation

DNA在四价平衡离子精胺溶液中,会发生电荷逆转,这个现象无法用经典的Poisson-Boltzman理论解释,一般认为与离子-离子关联、介电环境等有关。当改变溶液的介电常数,DNA-精胺复合物呈现不同的逆转及凝聚状态。本文首先利用动态光散射研究不同介电环境(溶液中加入乙醇、甘氨酸及6-氨基己酸)下DNA-精胺的电泳迁移率的变化,发现乙醇会有利于DNA发生电荷逆转,在0.5 mmol·L-1的精胺浓度下,DNA的电泳迁移率为-0.6×10-4cm2V-1S-1。当加入90%的乙醇后,DNA的电泳迁移率变为0.11×10-4cm2V-1S-1,然而向精胺-DNA溶液中加入甘氨酸,6-氨基己酸等两性物质之后,DNA的电泳迁移率随着两性物质浓度的增加而向负向移动。在此基础上,作者用原子力显微镜观察精胺-DNA复合物在不同浓度乙醇及两性物质下的表面形貌变化,发现随着乙醇浓度的增加,精胺-DNA复合物的凝聚形态会更加紧凑;而随着两性离子浓度的增加,精胺-DNA复合物的凝聚形态变得越来越松散,说明介电环境在精胺导致DNA构象变化及电荷逆转中起着一定的作用。研究不同介电环境下DNA的电泳迁移率及凝聚构象的影响,能对认识DNA凝聚的动力学特性提供帮助,而且有助于获得理想的非病毒载体,促进基因治疗的发展。

If DNA are in solution including tetravalent counter-ions spermine,the inversion of DNA charge will happen. This phenomenon cannot be explained by classical Poisson-Boltzman theories. Generally considered associated with the interaction of ionion,dielectric environment and so on. When the dielectric constant of solution change,DNA-spermine compounds present different reverse and condensed state. In this paper,first of all we study the change of the electrophoretic mobility of DNA-spermine on different dielectric environment（ adding ethanol solution,glycine and 6-amino caproicacid） by using dynamic light scattering. We found that ethanol are good for the charge reversal of spermine induced DNA. When the concentration of spermine is 0. 5 mmol·L- 1,DNA electrophoresis mobility is- 0. 6 × 10- 4cm2V- 1S- 1,when we added 90% ethanol to the DNA solution,DNA electrophoresis mobility is 0. 11 × 10- 4cm2V- 1S- 1. However,when we added zwitterionic species to spermine- DNA solution（ glycine,amino caproicacid）,DNA electrophoresis mobility will decrease with increasing the concentration of zwitterionic species. On this basis,we observed the morphologies of spermine- DNA complexes under different concentrations of ethanol and zwitterionic species by atomic force microscopy. We found that the condensed morphologies of spermine-DNA complexes will be more compact with ethanol concentration increasing. And the condensed morphologies of spermine- DNA complexes become more loose with zwitterionic species concentration increasing. The results show that the dielectric environment plays a certain role on DNA conformation change and charge reverse. We study the electrophoresis mobility and condensed conformation of DNA under different dielectric environment. This can help to recognize the dynamic characteristics of DNA condensation and obtain ideal non viral vector to promote the development of gene therapy.