FIGURE 1.

The mass spectrum, formation of selected ions, and cleavage rational of the CID MS/MS analysis of m/z 3122.5, the M+Na⁺ ion of methylated M₁₃-pLM produced by M. smegmatis ΔMSMEG_4241. A simplified structure is used where the OMe groups are left off from carbons 3 and 4, and the OMe group on carbon 2 is indicated by a single line. All fragments illustrated are complexed with a Na⁺ ion. The key ^1,5X and ^3,5A ions are indicated in red and blue, respectively; the less well understood E ions are shown in green. The formation of ^0,4A ions is not illustrated for simplicity but identified on the spectra itself with the blue bars emanating for the ^3,5A ions (28 atomic mass units apart). The formation of the major ion at m/z 2690 is not understood. One possibility is that it is formed via concerted loss of the phosphoglycerol moiety together with the single Man on Inositol at O-2 as indicated. The ion at m/z 2488 corresponds to a sodiated mannan chain released from the inositol with a hydrogen transfer yielding at 1-anhydromannose at the reducing end. Another major ion found in all spectra is that at m/z 237, which corresponds to sodiated phosphoglycerol.