Publication Date:
2012-06-28
Description:
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.
Print ISSN:
0305-1048
Electronic ISSN:
1362-4962
Topics:
Biology
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