Abdelkafi M, Leulliot N, Baumruk V, Bednárová L, Turpin P Y, Namane A, Gouyette C, Huynh-Dinh T, Ghomi M
Laboratoire de Physicochimie Biomoléculaire et Cellulaire, URA CNRS 2056, Université Pierre et Marie Curie, Paris, France.
Biochemistry. 1998 May 26;37(21):7878-84. doi: 10.1021/bi980011t.
Structures of the UCCG and UGCG tetraloops formed in octamer ribonucleotidic hairpin sequences, i.e., 5'-r[GC(UCCG)GC]-3' and 5'-r[GC(UGCG)GC]-3', have been studied in aqueous solution by methods of optical spectroscopy. UV absorption melting profiles of these short hairpins, containing only two closing GC base pairs in the stem, are consistent with a monophasic, completely reversible order-to-disorder transition and clearly confirm their unusual structural stability (with Tm congruent with 50 degrees C). To establish structural characteristics of these tetraloops, Raman and FTIR spectroscopies have been used and vibrational conformation markers arising from the phosphate backbone and various nucleosides have been analyzed. They have been assigned on the basis of known unambiguous vibrational markers established for DNA and RNA chains. Surprisingly, they are easily transferable to short oligonucleotidic sequences. Intensities and wavenumbers of these conformation markers have been monitored in the 0-70 degrees C temperature range, i.e., in going from an ordered to a disordered structure. The main structural features of the UCCG and UGCG tetraloops are similar to those previously found in the UUCG and UACG tetraloops by means of NMR and vibrational spectroscopies, except those of the second nucleosides of the tetraloops (rC and rG, respectively) which adopt a 3'-endo/anti rather than a 2'-endo/anti conformation.
已通过光谱学方法在水溶液中研究了在八聚体核糖核苷酸发夹序列（即5'-r[GC(UCCG)GC]-3'和5'-r[GC(UGCG)GC]-3'）中形成的UCCG和UGCG四环的结构。这些仅在茎中包含两个封闭GC碱基对的短发夹的紫外吸收熔解曲线与单相、完全可逆的有序到无序转变一致，并清楚地证实了它们不同寻常的结构稳定性（熔点约为50℃）。为了确定这些四环的结构特征，使用了拉曼光谱和傅里叶变换红外光谱，并分析了来自磷酸骨架和各种核苷的振动构象标记。它们是根据为DNA和RNA链建立的已知明确的振动标记进行归属的。令人惊讶的是，它们很容易转移到短寡核苷酸序列中。在0至70℃的温度范围内，即在从有序结构转变为无序结构的过程中，监测了这些构象标记的强度和波数。UCCG和UGCG四环的主要结构特征与之前通过核磁共振和振动光谱在UUCG和UACG四环中发现的特征相似，除了四环的第二个核苷（分别为rC和rG）采用3'-内/反式构象而非2'-内/反式构象。
