Identification of the position of the chlorine substituent. Left: interpretation of deuterium-labelling experiments in N. punctiforme ATCC 29133. Right: strain ∆nglO was fed palmitic-d2 acid as indicated. Black traces represent the mass spectrum of unlabelled 5 and coloured traces the experimentally observed mixture of unlabelled and labelled 5. Red boxes mark the theoretical centroided mass spectrum for a mixture of unlabelled and labelled 5 as indicated. Traces are normalized to M + 0. The increase in intensity at M + 1 with palmitic-7-7-d2 acid indicates replacement of a deuterium atom with chlorine.
