title: Solid-state NMR determination of sugar ring pucker in (13)C-labeled 2'-deoxynucleosides.
abstract: The H3'-C3'-C4'-H4' torsional angles of two microcrystalline 2'-deoxynucleosides, thymidine and 2'-deoxycytidine.HCl, doubly (13)C-labeled at the C3' and C4' positions of the sugar ring, have been measured by solid-state magic-angle-spinning nuclear magnetic resonance (NMR). A double-quantum heteronuclear local field experiment with frequency-switched Lee-Goldberg homonuclear decoupling was used. The H3'-C3'-C4'-H4' torsional angles were obtained by comparing the experimental curves with numerical simulations, including the two (13)C nuclei, the directly bonded (1)H nuclei, and five remote protons. The H3'-C3'-C4'-H4' angles were converted into sugar pucker angles and compared with crystallographic data. The delta torsional angles determined by solid-state NMR and x-ray crystallography agree within experimental error. Evidence is also obtained that the proton positions may be unreliable in the x-ray structures. This work confirms that double-quantum solid-state NMR is a feasible tool for studying sugar pucker conformations in macromolecular complexes that are unsuitable for solution NMR or crystallography.
authors.affiliation: Physical Chemistry, Arrhenius Laboratory, Stockholm University, 106 91 Stockholm, Sweden.
authors.forename: Lorens
authors.initials: L
authors.lastname: van Dam
authors.forename: Niels
authors.initials: N
authors.lastname: Ouwerkerk
authors.forename: Andreas
authors.initials: A
authors.lastname: Brinkmann
authors.forename: Jan
authors.initials: J
authors.lastname: Raap
authors.forename: Malcolm H
authors.initials: MH
authors.lastname: Levitt
mesh_terms: D002241:Carbohydrates / Q000737:chemistry*; D002244:Carbon; D018360:Crystallography, X-Ray; D004247:DNA / Q000737:chemistry*; D006859:Hydrogen; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008958:Models, Molecular; D009502:Neutrons; D009690:Nucleic Acid Conformation; D009705:Nucleosides / Q000737:chemistry*; D011522:Protons
chemical_list: D002241:Carbohydrates; D009705:Nucleosides; D011522:Protons; D002244:Carbon; D006859:Hydrogen; D004247:DNA