聚胺与DNA相互作用的相图

Phase Diagram on Interaction Between Polyamine and DNA

利用相图方法研究了聚胺(PA)与DNA的相互作用,初步考察了NaCl对精胺与DNA相互作用的影响。研究结果表明,聚胺与DNA之间不仅存在着强烈的静电作用,同时聚胺与DNA碱基对之间也存在着相互作用。在较低的精胺(SPM)浓度(0.025mmol/L)时就开始出现浊度,而在相同的条件下,亚精胺(SPD)-DNA体系和盐酸胍(GD)-DNA体系在聚胺浓度高达10mmol/L时浊度曲线仍无明显变化;SPD-DNA体系与GD-DNA体系的A260曲线相比,前者随着聚胺浓度的增加吸光度逐渐下降,说明SPD与DNA作用强于GD;由此可见聚胺所带正电荷越多,其与DNA的作用越强,水溶液条件下亚精胺(SPD)和GD与DNA间有较弱的相互作用,但不能使DNA产生相分离;加入NaCl后,由于外加电解质的静电屏蔽效应,SPM与DNA之间的相互作用减弱。NaCl浓度越大,二者之间相互作用越弱,SPM-DNA体系相图曲线的线性相关性越低。

The interaction between DNA and polyamine （PA） with different valency was studied via phase diagram. The influence of NaCl on the interaction between spermine（SPM） and DNA was also studied prima- rily. The result shows that there was electrostatic attraction between SPM and DNA, and interaction between SPM and DNA base pair as well. The SPM-DNA syetem began to show turbidity at a low SPM concentration （0. 025 retool/L） , while the turbidities of spermidine（SPD）-DNA and guanidine hydrochloride（ GD）-DNA systems didn＇t change much. With the increasing of polyamine, the A260 of the SPD-D／ ~ system reduced while the A260 of the GD-DNA system didn＇t change much when the concentration of polyamine was 10 retool/L, showing the interaction between SPD and DNA was stronger than that of GD-DNA system. So the higher the valeny of the polyamine, the stronger the interaction of the system. In aqueous solution, interactions between DNA and SPD or GD were weaker, and no phase separation was observed. After the addition of NaCl, the interaction between SPM and DNA will be baffled because of electrostatic-screening effect. The higher the NaCl concentration, the weaker the interaction and the worse the linearity of the phase curve of the system.