Mg2 ~+离子对多聚核糖肌苷酸和多聚核糖胞苷酸双链多聚核苷酸稳定性的影响
Mg2+ ion effect on stability of double-stranded popynucleotide formed by polyriboinosinic and polyribocytidilic chains
摘要：
用差示紫外光谱法研究了在接近生理条件（0.1M Na+，pH 7）下Mg ~（2+）对双链多核苷酸polyIpolyC（IC）热稳定性的影响。离子浓度（[Mg 2 +]）的初始增加导致熔化温度（Tm）的增加和由螺旋-卷曲转变引起的吸收增色值（hmax）的降低。Mg 2+与次黄嘌呤或胞嘧啶环的p-电子相互作用（阳离子-p-相互作用）。当[Mg 2 +]达到约10-4 M的临界值时，Tm降低，hmax增加到接近于在不存在镁的情况下观察到的值。当[Mg ~（2+）]=[Mg ~（2+）]Cr时，IC转变为新的结构状态。随着[Mg 2 +]>[Mg 2 +]cr，Tm再次增加，hmax缓慢降低。关键词：多核苷酸，热稳定性，金属离子。
英文摘要：
Mg2+ effect on the thermal stability of the double-stranded polynucleotide polyIpolyC (IC) under conditions close to physiological ones (0.1M Na+, pH7) was studied by the differential UV spectroscopy. The initial increase of the ion concentration ([Mg2+]) leads to the increase of the melting temperature (Tm) and to the decrease of the absorption hyperchromicity value that is caused by the helix-coil transition (hmax). Mg2+ interacts to p-electrons of hypoxanthine or cytosine rings (cation-p-interaction). When [Mg2+] reaches a critical value of about 10-4 M, Tm decreases and hmax increase to values close to one observed in the absence of magnesium. It is supposed that at [Mg2+]=[Mg2+]cr IC transits into a new structural state. With [Mg2+>[Mg2+]cr Tm increases again and hmax slowly decreases. Key words: polynucleotides, thermal stability, metal ions.
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