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Selective long-range 1H13C polarization transfer in nucleosides

✍ Scribed by William H. Gmeiner; J. William Lown

Publisher
John Wiley and Sons
Year
1992
Tongue
English
Weight
440 KB
Volume
30
Category
Article
ISSN
0749-1581

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✦ Synopsis

Abstract

Selective INEPT (INAPT) experiments were used to correlate the nitrogen‐ and carbon‐bound hydrogens of nucleosides with ^13^C resonances via ^2^J(C, H) and ^3^J(C, H). Such experiments are useful as part of a strategy to distinguish the imino hydrogens of uridine and thymidine, which cannot be accomplished on the basis of chemical shift. The strategy involves correlation of the imino hydrogen with C‐5 using INAPT and testing whether or not the C‐5 resonance is quaternary. Polarization transfer is ineffecient for most positions in nucleosides owing to the small long‐range couplings, except the H‐6C‐5 transfer in adenosine, which results in enhancement of the ^13^C resonance over its equilibrium value. The efficiency of polarization transfer from H‐3 to C‐5 of thymidine depends on the base‐paired status of the nucleoside indicating a change in the ^3^J(C, H) on base‐pair formation. This sensitivity to electronic reorganization on base‐pair formation makes the INAPT experiment a useful probe for the base‐paired status of nucleosides and of the electronic properties of uridine and thymidine analogues.

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