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首页> 外文期刊>Chemistry: A European journal >Discrimination in metal-ion binding to RNA dinucleotides with a non-bridging oxygen or sulfur in the phosphate diester link
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Discrimination in metal-ion binding to RNA dinucleotides with a non-bridging oxygen or sulfur in the phosphate diester link

机译：磷酸二酯键中具有非桥接氧或硫的金属离子与RNA二核苷酸结合的歧视

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Replacement of a non-bridging oxygen in the phosphate diester bond by a sulfur has become quite popular in nucleic acid research and is often used as a probe, for example, in ribozymes, where the normally essential Mg2+ is partly replaced by a thiophilic metal ion to reactivate the system. Despite these widely applied rescue experiments no detailed studies exist quantifying the affinity of metal ions to such terminal sulfur atoms. Therefore, we performed potentiometric pH titrations to determine the binding properties of pUp((S))U(3-) towards Mg2+, Mn2+, Zn2+, Cd2+, and Pb2+, and compared these data with those previously obtained for the corresponding pUpU(3-) complexes. The primary binding site in both dinucleotides is the terminal phosphate group. Theoretically, also the formation of 10-membered chelates involving the terminal oxygen or sulfur atoms of the (thio)phosphate bridge is possible with both ligands. The results show that Mg2+ and Mn2+ exist as open (op) isomers binding to both dinucleotides only at the terminal phosphate group. Whereas Cd(pUpU)(-) only exists as Cd(pUpU)(op)(-), Cd(pUp((S))U)(-) is present to about 64% as the S-coordinated macrochelate, Cd(pUp((S))U)(cl/PS)(-). Zn2+ forms with pUp((S))U(3-) three isomeric species, that is, Zn(pUp((S))U)(op)(-), Zn(pUp((S))U)(cl/PO)(-), and Zn(pUp((S))U)(cl/PS)(-), which occur to about 33, 12 (O-bound), and 55%, respectively. Pb2+ forms the 10-membered chelate with both nucleotides involving only the terminal oxygen atoms of the (thio)phosphate bridge, that is, no indication of S binding was discovered in this case. Hence, Zn2+ and Cd2+ show pronounced thiophilic properties, whereas Mg2+, Mn2+, and Pb2+ coordinate to the oxygen, macrochelate formation being of relevance with Pb2+ only.
机译：在核酸研究中，用硫代替磷酸二酯键中的非桥连氧已变得非常普遍，并经常用作探针，例如在核酶中，其中通常必不可少的Mg2 +被亲硫金属离子部分替代重新激活系统。尽管进行了广泛应用的救援实验，但尚无详细的研究来量化金属离子对此类末端硫原子的亲和力。因此，我们进行了电位pH滴定法以确定pUp（（S））U（3-）对Mg2 +，Mn2 +，Zn2 +，Cd2 +和Pb2 +的结合特性，并将这些数据与先前从相应的pUpU（3）获得的数据进行比较。 -）复合体。两个二核苷酸中的主要结合位点是末端磷酸基团。从理论上讲，两个配体都可能形成涉及（硫）磷酸酯桥的末端氧或硫原子的十元螯合物。结果表明，Mg2 +和Mn2 +以开放（op）异构体的形式存在，仅在末端磷酸基团与两个二核苷酸结合。 Cd（pUpU）（-）仅以Cd（pUpU）（op）（-）的形式存在，而Cd（pUp（（S））U）（-）的含量约为S配位的大螯合物Cd（ pUp（（S））U）（cl / PS）（-）。 Zn2 +与pUp（（S））U（3-）形成三个异构体，即Zn（pUp（（S））U）（op）（-），Zn（pUp（（S））U）（cl / PO）（-）和Zn（pUp（（S））U）（cl / PS）（-），它们分别出现在大约33、12（O结合）和55％的位置。 Pb2 +与两个仅与（硫代）磷酸酯桥的末端氧原子有关的核苷酸形成10元螯合物，即在这种情况下未发现S结合的迹象。因此，Zn2 +和Cd2 +表现出明显的亲硫特性，而Mg2 +，Mn2 +和Pb2 +与氧配位，大螯合物的形成仅与Pb2 +有关。

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