O'Connor T, Bina M
Department of Chemistry, Purdue University, West Lafayette, IN 47907.
J Biomol Struct Dyn. 1984 Dec;2(3):615-25. doi: 10.1080/07391102.1984.10507595.
Using Raman spectroscopy, we examined the ribose-phosphate backbone conformation, the hydrogen bonding interactions, and the stacking of the bases of the poly(U).poly(A).poly(U) triple helix. We compared the Raman spectra of poly(U).poly(A).poly(U) in H2O and D2O with those obtained for single-stranded poly(A) and poly(U) and for double-stranded poly(A).poly(U). The presence of a Raman band at 863 cm-1 indicated that the backbone conformations of the two poly(U) chains are different in the triple helix. The sugar conformation of the poly(U) chain held to the poly(A) by Watson-Crick base pairing is C3' endo; that of the second poly(U) chain may be C2' endo. Raman hypochromism of the bands associated with base vibrations demonstrated that uracil residues stack to the same extent in double helical poly(A).poly(U) and in the triple-stranded structure. An increase in the Raman hypochromism of the bands associated with adenine bases indicated that the stacking of adenine residues is greater in the triple helix than in the double helical form. Our data further suggest that the environment of the carbonyls of the uracil residues is different for the different strands.
我们使用拉曼光谱法研究了聚（U）·聚（A）·聚（U）三链螺旋的核糖 - 磷酸主链构象、氢键相互作用以及碱基堆积情况。我们将聚（U）·聚（A）·聚（U）在H₂O和D₂O中的拉曼光谱与单链聚（A）和聚（U）以及双链聚（A）·聚（U）的拉曼光谱进行了比较。863 cm⁻¹处拉曼峰的出现表明，在三链螺旋中两条聚（U）链的主链构象不同。通过沃森 - 克里克碱基配对与聚（A）结合的聚（U）链的糖构象为C3'内向型；第二条聚（U）链的糖构象可能是C2'内向型。与碱基振动相关的谱带的拉曼减色现象表明，尿嘧啶残基在双链聚（A）·聚（U）和三链结构中的堆积程度相同。与腺嘌呤碱基相关的谱带的拉曼减色现象增加表明，腺嘌呤残基在三链螺旋中的堆积比在双螺旋形式中更大。我们的数据进一步表明，不同链上尿嘧啶残基羰基的环境不同。
