Laboratory of Molecular Transformation, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan.
Nucleic Acids Res. 2012 Jul;40(12):5766-74. doi: 10.1093/nar/gks208. Epub 2012 Mar 1.
Developing applications for metal-mediated base pairs (metallo-base-pair) has recently become a high-priority area in nucleic acid research, and physicochemical analyses are important for designing and fine-tuning molecular devices using metallo-base-pairs. In this study, we characterized the Hg(II)-mediated T-T (T-Hg(II)-T) base pair by Raman spectroscopy, which revealed the unique physical and chemical properties of Hg(II). A characteristic Raman marker band at 1586 cm(-1) was observed and assigned to the C4=O4 stretching mode. We confirmed the assignment by the isotopic shift ((18)O-labeling at O4) and density functional theory (DFT) calculations. The unusually low wavenumber of the C4=O4 stretching suggested that the bond order of the C4=O4 bond reduced from its canonical value. This reduction of the bond order can be explained if the enolate-like structure (N3=C4-O4(-)) is involved as a resonance contributor in the thymine ring of the T-Hg(II)-T pair. This resonance includes the N-Hg(II)-bonded state (Hg(II)-N3-C4=O4) and the N-Hg(II)-dissociated state (Hg(II+) N3=C4-O4(-)), and the latter contributor reduced the bond order of N-Hg(II). Consequently, the Hg(II) nucleus in the T-Hg(II)-T pair exhibited a cationic character. Natural bond orbital (NBO) analysis supports the interpretations of the Raman experiments.
开发金属介导的碱基对（金属碱基对）的应用最近成为核酸研究的一个重点领域，理化分析对于设计和微调使用金属碱基对的分子器件非常重要。在这项研究中，我们通过拉曼光谱对 Hg(II)介导的 T-T（T-Hg(II)-T）碱基对进行了表征，揭示了 Hg(II)的独特物理和化学性质。在 1586 cm(-1) 处观察到一个特征拉曼标记带，并将其分配给 C4=O4 伸缩模式。我们通过同位素位移（O4 的 (18)O 标记）和密度泛函理论（DFT）计算证实了该分配。C4=O4 伸缩的异常低波数表明 C4=O4 键的键序从其规范值降低。如果烯醇式结构（N3=C4-O4(-)）作为胸腺嘧啶环中的共振贡献物参与 T-Hg(II)-T 对，则可以解释这种键序的降低。该共振包括 N-Hg(II)键合态（Hg(II)-N3-C4=O4）和 N-Hg(II)离解态（Hg(II+) N3=C4-O4(-)），后者降低了 N-Hg(II)的键序。因此，T-Hg(II)-T 对中的 Hg(II)核表现出阳离子特性。自然键轨道（NBO）分析支持拉曼实验的解释。
