壳聚糖与DNA作用过程中pH值对DNA电荷逆转及凝聚状态的影响

Effect of pH value on the DNA charge inversion and aggregation state during the interaction between DNA and chitosan

壳聚糖(chitosan)作为良好的基因载体能使DNA发生电荷逆转及凝聚,溶液p H值不同时,促使DNA发生电荷逆转的chitosan浓度及DNA的凝聚状态都会发生改变。作者通过单分子荧光电泳、动态光散射及原子力显微镜技术研究不同p H值下chitosan对DNA电荷逆转及凝聚状态的影响。首先单分子荧光电泳实验结果显示,p H值越大,导致DNA发生电荷逆转的chitosan浓度越大,同时还用动态光散射实验也得到类似的实验结果,进一步验证p H值在chitosan导致DNA的电荷逆转过程中的影响。DNA的电荷逆转主要与DNA的表面电荷量有关,但也可能与DNA的凝聚状态有关,本文用原子力显微镜观察到不同p H值及浓度下的chitosan导致DNA凝聚的凝聚状态的确不同,而且浓度高于一定值时,云母片上面看不到任何凝聚物的存在,也说明DNA电荷逆转的发生。可见,p H值在chitosan导致DNA电荷逆转及DNA的凝聚过程中起重要作用。

As a good gene delivery,chitosan could induce DNA charge inversion and condensation. At different p H value,the critical concentration of chitosan inducing DNA charge inversion and the morphologies of DNA condensation varied. The effects of chitosan on DNA charge inversion and morphology were investigated by single-molecule fluorescence electrophorotic（ SMFE）,dynamic light scattering（ DLS） and atomic force technology（ AFM） at different p H value in solution. The results of SMFE show that the critical concentration of chitosan inducing DNA charge inversion increases with p H value. The DLS experiment shows the similar result,which further indicates that p H value plays an important role in the process of DNA charge inversion induced by chitosan. The charge inversion of DNA is mainly related to the surface charge of DNA. However, it may be related to the morphologies of DNA condensation. The morphologies of DNA condensation change with p H value and chitosan concentration. No condensates can be observed on mica surface when the concentration is higher than a certain value,indicating that the DNA charge inversion occurs again.So chitosan plays an important role in DNA charge inversion and condensation.