title: Evaluating the effects of the nonplanarity of nucleic acid bases on NMR, IR, and vibrational circular dichroism spectra: a density functional theory computational study.
abstract: The pyramidalizations of N9/1 glycosidic nitrogens in DNA and RNA nucleosides, recently discovered and analyzed in their ultrahigh-resolution X-ray crystal structures ( Sychrovský ; et al. Nucleic Acid Res. 2009 , 37 , 7321. ), were found to have significant effects on the structural interpretation of the (3)J(C4/2-H1') and (3)J(C8/6-H1') NMR scalar couplings in purine/pyrimidine nucleosides. The calculated effects on IR and vibrational circular dichroism (VCD) spectra were only minor. The calculated structural deformations in nucleosides, depending on sugar-to-base orientation, gave rise to corrections in the phase shift of the Karplus equations for the (3)J(C8/6-H1') and (3)J(C4/2-H1') couplings ranging from -26° to +25° and from -5.7° to +2.0°, respectively. The sign alternation of this correction in syn and anti nucleosides arises from the stereoinversion of the N9/1 glycosidic nitrogen occurring upon reorientation of the glycosidic torsion. The effect was calculated consistently in the dG, dA, dC, dT, rA, and rG nucleosides. Utilization of the calculated phase-shift corrections in the design of Karplus equations for the (3)J couplings was suggested, and the effects on structural interpretation of the experimental couplings were evaluated.
authors.affiliation: Institute of Organic Chemistry and Biochemistry, v.v.i., Academy of Sciences of the Czech Republic, Flemingovo square 2, 166 10 Prague 6, Czech Republic. zuzana.vokacova@uochb.cas.cz
authors.forename: Zuzana
authors.initials: Z
authors.lastname: Vokácová
authors.forename: Lukás
authors.initials: L
authors.lastname: Trantírek
authors.forename: Vladimír
authors.initials: V
authors.lastname: Sychrovský
mesh_terms: D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000592:standards; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D012313:RNA / Q000737:chemistry*; D012015:Reference Standards; D013055:Spectrophotometry, Infrared; D014732:Vibration
chemical_list: D012313:RNA; D004247:DNA