A distinguishing feature of the lantibiotic family of cyclic peptides is the presence of thioethers. Treatment of a lantibiotic with an alkaline solution at high pH gives rise to a β-elimination reaction yielding the corresponding ring opened precursor, containing a dehydro-amino acid residue. We here reveal in a proof-of-concept study that a ring opened lantibiotic (mersacidin) can be captured for pull-down from a culture broth, subsequently released and identified by mass spectrometry.