title: Raman spectroscopic detection of the T-Hg II-T base pair and the ionic characteristics of mercury.
abstract: 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.
authors.affiliation: Laboratory of Molecular Transformation, Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aza-Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578, Japan.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Uchiyama
authors.forename: Takashi
authors.initials: T
authors.lastname: Miura
authors.forename: Hideo
authors.initials: H
authors.lastname: Takeuchi
authors.forename: Takenori
authors.initials: T
authors.lastname: Dairaku
authors.forename: Tomoyuki
authors.initials: T
authors.lastname: Komuro
authors.forename: Takuya
authors.initials: T
authors.lastname: Kawamura
authors.forename: Yoshinori
authors.initials: Y
authors.lastname: Kondo
authors.forename: Ladislav
authors.initials: L
authors.lastname: Benda
authors.forename: Vladimír
authors.initials: V
authors.lastname: Sychrovsky
authors.forename: Petr
authors.initials: P
authors.lastname: Bour
authors.forename: Itaru
authors.initials: I
authors.lastname: Okamoto
authors.forename: Akira
authors.initials: A
authors.lastname: Ono
authors.forename: Yoshiyuki
authors.initials: Y
authors.lastname: Tanaka
mesh_terms: D020029:Base Pairing; D002412:Cations / Q000737:chemistry; D008628:Mercury / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D013941:Thymine / Q000737:chemistry*
chemical_list: D002412:Cations; D008628:Mercury; D013941:Thymine