Shindo H, Simpson R T, Cohen J S
J Biol Chem. 1979 Sep 10;254(17):8125-8.
A highly homogeneous 145-base-pair fragment of double helical poly(dA-dT) . poly(dA-dT) was obtained by micrococcal nuclease digestion of a semisynthetic chromatin prepared from the nucleosome core histones (H2A, H2B, H3, H4) and the synthetic polydeoxyribonucleotide. In contrast to higher molecular weight alternating copolymers, this fragment displayed two resolved 31P NMR signals, separated by 24 Hz at 10.93 MHz. The two signals were of equal intensity at all temperatures less than the Tm for the fragment. Analyses of the possible origins for the two reasonances leads to the conclusion that the phosphodiester backbone of this DNA contains two distinct phosphorus environments, probably in an alternating array. We suggest that this may indicate the presence of sequence-dependent local variation in the helical structure of DNA in general.
通过微球菌核酸酶消化由核小体核心组蛋白（H2A、H2B、H3、H4）和合成多脱氧核糖核苷酸制备的半合成染色质，获得了高度均一的145个碱基对的双螺旋聚（dA-dT）·聚（dA-dT）片段。与高分子量交替共聚物不同，该片段显示出两个分辨的31P NMR信号，在10.93 MHz时相隔24 Hz。在低于该片段熔点的所有温度下，这两个信号强度相等。对这两个共振可能来源的分析得出结论，该DNA的磷酸二酯主链包含两个不同的磷环境，可能呈交替排列。我们认为，这可能总体上表明DNA螺旋结构中存在序列依赖性局部变化。
