Signs of heteronuclear spin–spin coupling constants in 15N-acetamide

✍ Scribed by Antonio De Marco; Miguel Llinás

• Publisher: John Wiley and Sons
• Year: 1979
• Tongue: English
• Weight: 663 KB
• Volume: 12
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270120804

✦ Synopsis

Abstract

By using digital deconvolution to improve spectral resolution, earlier NMR studies on ^15^N‐enriched acetamide have been revised and extended to determine the signs of the heteronuclear spin‐spin coupling constants. ^1^J(^13^CO^15^N), ^2^J(^13^CH~3~^15^N) and ^3^J(C^1^H~3~^15^N) are negative while ^3^J(^1^H^13^CH~3~)>0. The results, interpreted on the basis of the ‘selective decoupling’ formalism, were confirmed by computer simulation of the double resonance spectra. It is shown that ^2^J(^1^H‐α^13^CO) is significantly larger than ^2^J(^1^H^N 13^CO). Thus, jointly with {^1^H‐β}‐^13^C′ double resonance experiments, {^1^H‐α}‐^13^C′ experiments ought to be most helpful when assigning peptide group carbonyl resonances. The study provides valuable information for the interpretation of heteronuclear coupling constants in polypeptides.