FIG. 6.

sigM expression inhibits PDIM synthesis. A. Nonpolar surface lipids were extracted and subjected to silica TLC in comparison with a PDIM standard B. Mass spectrometry analysis of lipids corresponding to the uppermost spot in the PDIM triad, which were directly scraped onto nanospray tips, extracted by solvent, and analyzed by nanospray electrospray ionization-MS, yielding ions that correspond to those expected from an alkane series of ammonium (m/z 1371, 1385, 1399, 1413, and 1427) and sodium (m/z 1376, 1390, 1404, 1418, and 1432) adducts of PDIM. C and D. CID mass spectra of the ion at m/z 1390.4 yielded fragment ions corresponding to sodium adducts of products that have lost one (m/z 951.9) or two (m/z 513.5) mycocerosic acids (m/z 461).