Smith F W, Lau F W, Feigon J
Department of Chemistry and Biochemistry, University of California, Los Angeles 90024.
Proc Natl Acad Sci U S A. 1994 Oct 25;91(22):10546-50. doi: 10.1073/pnas.91.22.10546.
The structure formed by the DNA oligonucleotide d(G3T4G3) has been studied by one- and two-dimensional 1H NMR spectroscopy. In NaCl solution, d(G3T4G3), like d(G4T4G4) (Oxy-1.5), forms a dimeric quadruplex with the thymines in loops across the diagonal of the end quartets. Unlike Oxy-1.5, the dimer is not symmetric, and both monomer strands are observed in NMR spectra. Three quartets are formed from the GGG tracts. Glycosidic conformations of the guanines are 5'-syn-syn-anti-(loop)-syn-anti-anti in one strand and 5'-syn-anti-anti-(loop)-syn-syn-anti in the other strand. Thus, the stacking of the quartets (tail-to-tail, head-to-tail) is unlike all previously described fold-back (tail-to-tail, head-to-head) and parallel-stranded (head-to-tail, head-to-tail) quadruplexes.
已通过一维和二维¹H NMR光谱研究了DNA寡核苷酸d(G3T4G3)形成的结构。在NaCl溶液中，d(G3T4G3)与d(G4T4G4)（Oxy - 1.5）一样，形成二聚体四重螺旋结构，其中胸腺嘧啶位于末端四重体对角线上的环中。与Oxy - 1.5不同，该二聚体不对称，并且在NMR光谱中观察到两条单体链。由GGG片段形成了三个四重体。一条链中鸟嘌呤的糖苷构象为5'-顺式-顺式-反式-（环）-顺式-反式-反式，另一条链中为5'-顺式-反式-反式-（环）-顺式-顺式-反式。因此，四重体的堆积方式（尾对尾、头对尾）不同于所有先前描述的回折式（尾对尾、头对头）和平行链式（头对尾、头对尾）四重螺旋结构。
