Figure 2: Lipid identification. A) The exact mass was determined for the three lipid families observed in the lipid extract of the mce1 operonmutant strain. B) Tandem mass spectrometric analysis of the alpha (m/z 1136.17; top) and methoxy (m/z 1252.29; bottom) mycolic acids; in each case meromycolate chain (shaded portion) is lost as a neutral fragment and charge is retained on the alpha chain.