Chou S H, Tseng Y Y, Wang S W
Institute of Biochemistry, Department of National Chung-Hsing University, Taichung 40227, Taiwan.
J Mol Biol. 1999 Mar 26;287(2):301-13. doi: 10.1006/jmbi.1999.2564.
Single-residue d(Pu1NPu2) (Pu1.Pu2=G.A, G.G or A.A) hairpin loops can be stably closed by sheared purine.purine pairs. These special motifs have been found in several important biological systems. We now extend these loop-closing base-pairs to a sheared purine. pyrimidine (A.C) pair at a neutral pH condition. High-resolution NMR spectroscopy, distance geometry, and molecular dynamics methods were used to study d(GTACANCGTAC) oligomers. Numerous idiosyncratic nuclear Overhauser enhancements, especially those across the A.C base-pair between C4NH2left and right arrow AH1', C4NH2left and right arrow AH2, and CH5left and right arrow AH2 proton pairs, clearly define the novel sheared nature of the closing A.C base-pair. This novel base-pair is possibly present in several biological systems and in two single-stranded DNA aptamers selected from oligonucleotide libraries.
单残基d(Pu1NPu2)（Pu1.Pu2 = G.A、G.G或A.A）发夹环可通过剪切的嘌呤-嘌呤对稳定闭合。这些特殊基序已在几个重要的生物系统中被发现。我们现在将这些环闭合碱基对扩展到中性pH条件下的剪切嘌呤-嘧啶（A.C）对。利用高分辨率核磁共振光谱、距离几何和分子动力学方法研究了d(GTACANCGTAC)寡聚物。大量独特的核Overhauser增强效应，特别是那些跨越C4NH2左箭头AH1'、C4NH2左箭头AH2以及CH5左箭头AH2质子对之间A.C碱基对的效应，清楚地定义了闭合A.C碱基对的新型剪切性质。这种新型碱基对可能存在于几个生物系统以及从寡核苷酸文库中筛选出的两个单链DNA适配体中。
