Figure 4.

Gas chromatograms of fatty acid methyl esters recovered from purified protein preparations. Analyses of a preparation of LppX (black line) and Rv3849 (a M. tuberculosis 14.7 kDa cellular protein of unknown function) (gray line) are shown. Fatty acid methyl esters prepared from the equivalent of 50 μg of purified proteins were injected in both cases. Approximately 0.55 mol of fatty acids were recovered per mole of purified LppX. Peaks of similar intensities found in both protein preparations were identified by GC/MS as phthalates, likely to originate from plastic contamination. Heptadecanoic acid (C17:0) methyl ester (Sigma) was used as an internal standard for fatty acid quantification.