不同金属离子对PolyrA PolyrU在浓度和温度变化下构象转变的影响
Effects of different metal cations on conformational transitions in PolyrA PolyrU under concentration and temperature changes
摘要：
根据平衡结合模型理论，计算了Mg ~（2+），Ni ~（2+），Cd ~（2+）存在下，Na ~+浓度为0.1M时，poly rA poly rU体系的相图。结合常数（KA，KU，KAU，KA 2U）已被确定，最好的协议与早期的实验结果正在观察。图与Mg ~（2+）的计算示出允许获得令人满意的结果，如果使用稳定的平均常数的离子结合到所有提到的结构的多核苷酸。但在Ni 2+和Cd 2+的情况下，必须考虑到离子浓度的常数依赖性，特别是在高离子含量的情况下，单链聚A分子的压缩出现。结果表明，造成Ni ~（2+）和Cd ~（2+）图谱差异的主要因素是它们与poly A结合常数的显著变化。温度依赖性的构象转换得到的UV光谱为低聚合物浓度与那些通过IR和VCD光谱在高含量的这些分子，因此，在溶液中的金属离子。澄清了早期观察到的不成比例2->3转变的不可逆性的差异和特殊性。
英文摘要：
By the theory based on the equilibrium binding model, phase diagrams have been calculated for the poly rA poly rU system in the presence of Mg2+, Ni2+, Cd2+, with Na+ 0.1 M. Binding constants (KA, KU, KAU, KA2U) have been determined, the best agreement with the early experimental results being observed. Calculations of diagrams with Mg2+ are shown to permit obtaining satisfactory results if steady mean constants of ion binding to polynucleotides of all the mentioned structures are used. But in the cases with Ni2+ and Cd2+, constants dependences on ion concentrations must be taken into account, especially with high ion contents in the presence of which compaction of molecules of single-stranded poly A emerges. It has been revealed that the main factor being responsible for differences in diagrams for Ni2+ and Cd2+ is a significant variation of their constants of binding to poly A. Temperature dependences of conformational transitions obtained by UV spectroscopy for low polymer concentrations are compared with those obtained by IR and VCD spectroscopy at high contents of these molecules and, accordingly, metal ions in solution. Differences and peculiarities conditioning irreversibility of the earlier observed disproportional 2->3 transition are clarified.
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