TABLE 3.

Mr observed by MALDI-TOF MS for lipid A structures of E. coli lpxL mutant strain MLK 217 and MKM10 (MLK217 complemented with FTT0232c)

Mr observeda (exact)Mr calculated (exact)ΔMd (ppm)Lipid structure (fatty acid composition)
1,825.17b1,825.24392× C14:0, 4× C14:0(3-OH), 2× P
1,745.211,745.27382× C14:0, 4× C14:0(3-OH), P
1,614.981,615.0438C14:0, 4× C14:0(3-OH), 2× P
1,535.011,535.0845C14:0, 4× C14:0(3-OH), P
1,404.791,404.84414× C14:0(3-OH), 2× P
1,324.821,324.88434× C14:0(3-OH), P
1,178.591,178.65483× C14:0(3-OH), 2× P
1,098.631,098.68473× C14:0(3-OH), P
1,851.23c1,851.2611C16:1, C14:0, 4× C14:0(3-OH), 2× P
1,771.24c1,771.3629C16:1, C14:0, 4× C14:0(3-OH), P
  • a Species were detected in negative-ion mode as (M-H) by MALDI-TOF MS analysis (monoisotopic masses are reported).

  • b Masses in boldface were detected exclusively in the complemented strain MKM10 (MLK217 complemented with FTT0232c).

  • c Lipid A species that appeared in lpxL mutant strain MLK217 containing additional C16:1 fatty acids.

  • d ΔM, mass difference between the observed and calculated mass of various lipid A species.