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首页> 外文期刊>Chemistry: A European journal >Effects of (N7)-Coordinated Nickel(II), Copper(II), or Platinum(II) on the Acid-Base Properties of Guanine Derivatives and Other Related Pruines~[not=]
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Effects of (N7)-Coordinated Nickel(II), Copper(II), or Platinum(II) on the Acid-Base Properties of Guanine Derivatives and Other Related Pruines~[not=]

机译：（N7）配位的镍（II），铜（II）或铂（II）对鸟嘌呤衍生物和其他相关嘌呤的酸碱性能的影响〜[not =]

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摘要

The effect of Ni~2+, Cu~2+, and cis-a_2Pt~2+ or trans-a_2Pt~2+ (where a = NH_3 or CH_3NH_2), if coordinated to the N7 site of guanine residues, on the acid-base properties of complexes containing guanine derivatives as ligandsis ocnsidered. Teh various acidity constants were determiend bypotentiometric pH titrations. Over 60 acidity constants are listed; about half of these are new. In many nstances micro acidity ocnstants have been derived that allow a quantification ofhte intrinsic acid - base properties of a certain site, which are other-wise blurred by the pK_a values of overlapping buffer regions. This material allows many comparisons; maong these is the observation that te acidifying properties of (N7)-coordinated divalent metal ions on the corresponding (N1)H sites in a guanine derivative decrease in the folowing series: Cu~2+ (#DELTA#pK_a = 2.2 +- 0.3) > Ni~2+ (1.7 +- 0.15) > Pt~2+ (1.4 +- 0.1) ～ Pd~2+ (1.4). The data also indicate that the effects are similar for guanine and hypoxanthine residues, but that they are more pronounced for adening derivatives because in the latter case a (N7)-bound M~2+ affects a (N1)H~+ site; hence, a further charge effect is operative here. The available material does not yet allow certain prediction of the more subtle differences occurring be tween the cis and trans isomers of Pt~2+ complxes, but replacement of, for example, NH_3 in the coordination sphere of Pt~2+ with CH_3NH_2 has an effect. Of course, as one might expect, the effect of (N7)-bound Pt~2+ in guanine nucleotide complexes si smaller on teh more remote phosphate groups than it is on the closer (N1)H sites. By evaluation (by means of micro acidity constants) of data available for hypoxanthine derivatives it is also shown that (N1)~--bound Pt~2+ has an acidifying effect on the (N7)H~+ site comparalbe to that of (N7)-coordinated Pt~2+ on the (N1)H site.
机译：如果与鸟嘌呤残基的N7位配位，则Ni〜2 +，Cu〜2 +和顺式a_2Pt〜2 +或反式a_2Pt〜2 +（其中a = NH_3或CH_3NH_2）的作用对酸-含有鸟嘌呤衍生物作为配体的配合物的基本性质。通过电位滴定pH滴定法测定各种酸度常数。列出了60多个酸度常数。其中大约一半是新的。在许多情况下，已经获得了微酸性助剂，其允许定量某些位点的固有酸-碱性质，否则它们会因重叠的缓冲区的pK_a值而模糊。这种材料可以进行很多比较;其中一个发现是鸟嘌呤衍生物的相应（N1）H位上的（N7）配位的二价金属离子的酸化特性在以下序列中降低：Cu〜2 +（＃DELTA＃pK_a = 2.2 +-0.3 ）> Ni〜2 +（1.7 +-0.15）> Pt〜2 +（1.4 +-0.1）〜Pd〜2 +（1.4）。数据还表明，鸟嘌呤和次黄嘌呤残基的作用相似，但对加成衍生物的作用更明显，因为在后一种情况下，结合（N7）的M〜2 +影响（N1）H〜+位点;因此，在这里进一步起作用。现有的材料尚不能确定Pt〜2 +化合物的顺式和反式异构体之间发生的更细微差别的某些预测，但是例如用CH_3NH_2替换Pt〜2 +配位域中的NH_3时，影响。当然，正如人们可能期望的那样，在更远端的磷酸基团上，鸟嘌呤核苷酸复合物中与（N7）结合的Pt〜2 +的作用比在更近的（N1）H位点上的作用小。通过对次黄嘌呤衍生物可用数据的评估（通过微酸度常数），还表明（N1）〜-结合的Pt〜2 +对（N7）H〜+位点的酸化作用与（ （N1）H位点上N7）配位的Pt〜2 +。

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