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首页> 外文期刊>Chemistry: A European journal >Stabilities and isomeric equilibria in aqueous solution of monomeric metal ion complexes of adenosine 5'-diphosphate (ADP~(3-)) in comparison with those of adenosine 5'-monophosphate (AMP~(2-))
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Stabilities and isomeric equilibria in aqueous solution of monomeric metal ion complexes of adenosine 5'-diphosphate (ADP~(3-)) in comparison with those of adenosine 5'-monophosphate (AMP~(2-))

机译：5'-二磷酸腺苷（ADP〜（3-））的单体金属离子配合物与5'-单磷酸腺苷（AMP〜（2-））的稳定性和异构体平衡

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Under experimental conditions in which the self-association of the adenine phosphates (AP), that is, of adenosine 5'-monophosphate (AMP~(2-)) and adenosine 5'-diphosphate (ADP~(3-)), is negligible, potentiometric pH titrations were carried out to determine the stabilities of the M (H: AP) and M(AP) complexes where M~(2+) = Mg~(2+), Ca~(2+), Sr~(2+), Ba~(2+), Mn~(2+), Co~(2+), Ni~(2+), Cu~(2+), Zn~(2+), or Cd~(2+), (25 deg C; I = 0.1 M, NaNO_3). It is concluded that in the M(H; AMP)~+ species M~(2+) is bound at the adenine moiety and in the M(H; ADP) complexes at the diphosphate unit; however, the proton resides in both types of monoprotonated complexes at the phosphate residue. The stabilities of nearly all the M(AMP) and M(ADP)~- complexes are significantly larger than what is expected for a sole coordination of M~(2+) to the phosphate residue. This increased complex stability is attributed, in agreement with previous ~1H NMR shift studies and further information existing in the literature, to the formation of macrochelates of the phosphate-coordinated metal ions with N7 of the adenine residues. On the basis of recent measurements with simple phosphate monoesters and phosphonate ligands (R-MP~(2-)) as well as with diphosphate monoesters (R-DP~(3-)), where R is a noncoordinating and noninhibiting residue, the increased stabilities of the M(AMP) and M(ADP)~- complexes due to the M~(2+)-N7 interaction could be evaluated and the extent of macrochelate formation calculated. The results show that the formation degrees of the macrochelates for the complexes of the alkaline earth ions are small (about 15% at the most), whereas for the 3d metal ions as well as for Zn~(2+) and Cd~(2+) the formation degress vary between about 15% (Mn~(2+)) and 75% (Ni~(2+)) with values of about 40 and 50% for Zn~(2+) and Cu~(2+), respectively. It is interesting to note, taking earlier results for M(ATP)~(2-) complexes also into account (ATP~(4-) = adenosine 5'-triphosphate), that for a given metal ion in nearly all instances the formation degrees of the macrochelates are within the error limits the same for M(AMP), M(ADP)~- and M(ATP)~(2-) complexes; except for Co~(2+) and Ni~(2+) it holds M(AMP) > M(ADP)~- approx M(ATP)~(2-). This result is astonishing if one considers that the absolute stability constants of these complexes, which are determined largely by the affinity of the phosphate residues, can differ by more than two orders of magnitude.The impact and conclusions of these observations for biological systems are shortly lined out.
机译：在实验条件下，腺嘌呤磷酸酯（AP），即5'-单磷酸腺苷（AMP〜（2-））和5'-二磷酸腺苷（ADP〜（3-））的自缔合进行了微不足道的电位pH滴定，以确定M（H：AP）和M（AP）配合物的稳定性，其中M〜（2+）= Mg〜（2 +），Ca〜（2 +），Sr〜 （2 +），Ba〜（2 +），Mn〜（2 +），Co〜（2 +），Ni〜（2 +），Cu〜（2 +），Zn〜（2+）或Cd〜 （2 +），（25摄氏度; I = 0.1 M，NaNO_3）。结论是在M（H; AMP）〜+物种中，M〜（2+）结合在腺嘌呤部分和二磷酸单元的M（H; ADP）配合物中;然而，质子在磷酸盐残基处同时存在于两种类型的单质子化复合物中。几乎所有的M（AMP）和M（ADP）〜-配合物的稳定性都比单独的M〜（2+）与磷酸残基配位所期望的要大得多。与先前的〜1H NMR位移研究和文献中存在的更多信息相一致，这种增加的复合物稳定性归因于磷酸配位金属离子与腺嘌呤残基N7的大螯合物的形成。根据最近对简单的磷酸单酯和膦酸酯配体（R-MP〜（2-））以及二磷酸单酯（R-DP〜（3-））的测量结果，其中R为非配位和非抑制残基，可以评估由于M〜（2 +）-N7相互作用而增加的M（AMP）和M（ADP）〜-配合物的稳定性，并计算大螯合物的形成程度。结果表明，碱土金属离子配合物的大螯合物的形成度很小（最多约15％），而3d金属离子以及Zn〜（2+）和Cd〜（2 +）的形成偏差在15％（Mn〜（2+））和75％（Ni〜（2+））之间变化，Zn〜（2+）和Cu〜（2+ ）， 分别。有趣的是，考虑到M（ATP）〜（2-）配合物的早期结果（ATP〜（4-）= 5'-三磷酸腺苷），对于给定的金属离子，几乎在所有情况下大螯合物的度数在M（AMP），M（ADP）〜-和M（ATP）〜（2-）配合物的误差范围内;除了Co〜（2+）和Ni〜（2+）以外，它的M（AMP）> M（ADP）〜-大约M（ATP）〜（2-）。如果人们认为这些复合物的绝对稳定性常数（主要由磷酸盐残基的亲和力决定）可能相差两个以上数量级，那么这一结果将是惊人的。这些观察结果对生物系统的影响和结论很快就会出现。排好队。

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