Confirmation of the structure of nisin by complete 1H n.m.r. resonance assignment in aqueous and dimethyl sulphoxide solution

Abstract

The chemical structure of the peptide antibiotic nisin has been confirmed by the unambiguous sequence-specific assignment of its ¹H n.m.r. spectrum using a range of 2-D n.m.r. techniques. Nisin was examined in both aqueous (sodium phosphate buffer, pH 2.25) and dimethyl sulphoxide–trifluoroacetic acid solution. Amino acid spin systems were identified from observation of relayed connectivity patterns in the HOHAHA spectrum. Sequential assignments were accomplished with the aid of NOESY and relayed-NOESY spectra. In addition, the locations of the five thioether ring systems were confirmed. The detailed n.m.r. analysis provides strong evidence for the structure originally proposed on the basis of chemical degradation studies.