Solid-State NMR Determination of Sugar Ring Pucker in 13C-Labeled 2'-Deoxy Nucleosides,

L. van Dam, N. Ouwerkerk, A. Brinkmann, J. Raap, and M. H. Levitt,
Biophys. J. 83, 2835-2844, (2002).
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The H3'-C3'-C4'-H4' torsional angles of two microcrystalline 2'-deoxynucleosides, thymidine and 2'-deoxycytidine.HCl, doubly 13C-labeled at the C3' and C4' positions of the sugar ring, have been measured by solid-​state magic-​angle-​spinning 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 13C nuclei, the directly bonded 1H 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 which are unsuitable for solution NMR or crystallography.