TABLE 2.

Structural interpretations of lipid A species detected by mass spectrometry in this study

m/zLipid A modificationsa
1572Deacylation
1588Deacylation and hydroxylation
1668Deacylation and hydroxylation (pyrophosphate lipid A)b
1711Deacylation, hydroxylation, and phosphoethanolamine attachment
1798(Unmodified)
1810Deacylation and palmitoylation
1814Hydroxylation
1826Deacylation, palmitoylation, and hydroxylation
1894Hydroxylation (pyrophosphate lipid A)b
1921Phosphoethanolamine attachment
1937Hydroxylation and phosphoethanolamine attachment
1945Aminoarabinose attachment and hydroxylation
1949Deacylation, palmitoylation, hydroxylation, and phosphoethanolamine attachment
2036Palmitoylation
2052Palmitoylation and hydroxylation
2132Hydroxylation and palmitoylation (pyrophosphate lipid A)b
2159Palmitoylation and phosphoethanolamine attachment
2175Palmitoylation, hydroxylation, and phosphoethanolamine attachment
  • a Interpretations were based on previous papers (17, 24, 39, 44).

  • b Pyrophosphate lipid A has a pyrophosphate residue instead of a monophosphate residue at position 1 of the disaccharide glucosamine of lipid A. How the synthesis of pyrophosphate lipid A is regulated is not known (44).