Hirao I, Kawai G, Yoshizawa S, Nishimura Y, Ishido Y, Watanabe K, Miura K
Laboratory of Pharmaceutical Chemistry, Tokyo College of Pharmacy, Japan.
Nucleic Acids Symp Ser. 1993(29):205-6.
The extraordinarily stable hairpin-like structure formed by a short DNA fragment, d(GCGAAGC), has been studied by NMR spectroscopy and UV melting behaviour. The fragment is folded back between A4 and A5, and forms two terminal G-C base pairs and a non-Watson-Crick G-A base pair. All the nucleotides adopt C2'-endo sugar puckers. Both G1C2G3A4 and A5G6C7 moieties have characteristics of B-form geometry and within each moiety all the bases are involved in extensive base-base interactions. Distortion from B-form occurs in only the three torsion angles between A4 and A5 residues, which causes a sharp turn in the structure. There is no clear distinction between a stem and a loop region, as observed in usual hairpin structures, so that we classify it as a turn (hairpin-turn) structure. In addition to the thermal stability, this fragment is more stable towards the attack of some nucleases than other single-stranded as well as usual hairpin DNA fragments.
一个短DNA片段d(GCGAAGC)形成的极其稳定的发夹状结构，已通过核磁共振光谱和紫外熔解行为进行了研究。该片段在A4和A5之间回折，形成两个末端G-C碱基对和一个非沃森-克里克G-A碱基对。所有核苷酸均采用C2'-内向型糖构象。G1C2G3A4和A5G6C7部分均具有B型几何特征，且在每个部分内，所有碱基都参与广泛的碱基-碱基相互作用。仅在A4和A5残基之间的三个扭转角处出现与B型的扭曲，这导致结构中出现急转弯。与通常的发夹结构不同，该结构中没有明显的茎区和环区之分，因此我们将其归类为转角（发夹-转角）结构。除了热稳定性外，该片段对某些核酸酶攻击的稳定性高于其他单链以及通常的发夹DNA片段。
