Carbon-13 chemical shielding tensors in l-threonine

Nathan Janes, Subramanian Ganapathy, Eric Oldfield

Research output: Contribution to journalArticle

Abstract

The carbon-13 chemical shielding tensors of the amino acid L-threonine have been determined by solid state proton-enhanced NMR of a single crystal at 3.52 T. For the first time a carbinol shielding tensor is determined quantitatively and unambiguously: the most shielded axis lies 4° from the CO bond. A coordinate system which approximates the alpha carbon tensor orientation is proposed, and it is suggested that this "local symmetry" may be general to many amino acid alpha carbons. The carboxyl and methyl tensor orientations closely approximate previously established "local symmetry," although the methyl (Cγ) C3v symmetry is slightly disrupted, apparently by the neighboring (Oγ) oxygen. The influence of the carbon-nitrogen dipolar interaction on the observed spectra is discussed, and used to make unique assignments for the carboxyl, alpha, and beta carbon tensors.

Original languageEnglish (US)
Pages (from-to)111-121
Number of pages11
JournalJournal of Magnetic Resonance (1969)
Volume54
Issue number1
DOIs
StatePublished - Aug 1983

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