Effect of the N<sup>6</sup>-Methyl Group of the Adenine Ring on the Stacking Interaction
作者:Toshio Itahara
DOI:10.1246/bcsj.73.1621
日期:2000.7
In an effort to determine the effects of N6-methylation of the adenine ring on stacking, the molecular aggregation of 9,9′-(α,ω-alkanediyl)bis[6-(dimethylamino)purine] (1) and of 9,9′-(α,ω-alkanediyl)bis[6-(methylamino)purine] (2) were compared with that of 9,9′-(α,ω-alkanediyl)bis[adenine] (3) by NMR spectroscopy. The obtained concentration effects indicate that N6-methylation resulted in an increase in the population of intermolecular aggregates in the buffer solution at pD 7.0, and had an additive effect on the aggregation. It can be interpreted as a hydrophobic effect of the N6-methyl groups. The aggregation of 1 and 2 depended on the length of the polymethylene chains in a similar manner as that of 3, when the measurements were made on the solution of low concentrations. This suggests that the aggregates of 1, 2, and 3 were similar to each other through stacking between two adenine rings. Furthermore, the chemical shifts of the N6-methyl groups were slightly influenced by the length of the polymethylene chains and the changes of temperature. The N6-methyl group may be located outside the stacking. On the basis of these data, it may be concluded that the N6-methylation enhanced the stacking, but had little influence on the conformation of the stacking.
为了确定腺嘌呤环 N6-甲基化对堆积的影响,研究人员对 9,9′-(α,ω-烷二基)双[6-(二甲基氨基)嘌呤](1)和 9、9′-(α,ω-烷二基)双[6-(甲基氨基)嘌呤](2)与 9,9′-(α,ω-烷二基)双[腺嘌呤](3)的比较。所获得的浓度效应表明,N6-甲基化会导致 pD 7.0 缓冲溶液中分子间聚集体的数量增加,并对聚集产生叠加效应。这可以解释为 N6-甲基的疏水效应。在低浓度溶液中进行测量时,1 和 2 的聚集取决于聚亚甲基链的长度,其方式与 3 相似。这表明 1、2 和 3 的聚合体通过两个腺嘌呤环之间的堆叠而彼此相似。此外,N6-甲基的化学位移受到聚亚甲基链长度和温度变化的轻微影响。N6-甲基可能位于堆叠之外。根据这些数据,可以得出结论:N6-甲基化增强了堆积,但对堆积的构象影响不大。