Figure 4. Sequencing of the peptidoglycan cross-link of lactoyl-peptides by tandem mass spectrometry.
The figure illustrates the capacity of the method to discriminate isomers containing 3→3 (A) and 4→3 (B) cross-links. Fragments specific of each isomer are shown in red. L, D-Lac; A, L-Ala or D-Ala; a, C-terminal D-Ala; E, D-Glu; DAP, diaminopimelic acid. All dimers present in peptidoglycan preparations from mutant M1 were identified by this method.