TABLE 3.

M_r 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)
1,825.17b	1,825.24	39	2× C14:0, 4× C14:0(3-OH), 2× P
1,745.21	1,745.27	38	2× C14:0, 4× C14:0(3-OH), P
1,614.98	1,615.04	38	C14:0, 4× C14:0(3-OH), 2× P
1,535.01	1,535.08	45	C14:0, 4× C14:0(3-OH), P
1,404.79	1,404.84	41	4× C14:0(3-OH), 2× P
1,324.82	1,324.88	43	4× C14:0(3-OH), P
1,178.59	1,178.65	48	3× C14:0(3-OH), 2× P
1,098.63	1,098.68	47	3× C14:0(3-OH), P
1,851.23c	1,851.26	11	C16:1, C14:0, 4× C14:0(3-OH), 2× P
1,771.24c	1,771.36	29	C16:1, C14:0, 4× C14:0(3-OH), P

^aSpecies were detected in negative-ion mode as (M-H)⁻ by MALDI-TOF MS analysis (monoisotopic masses are reported).

^bMasses in boldface were detected exclusively in the complemented strain MKM10 (MLK217 complemented with FTT0232c).

^cLipid A species that appeared in lpxL mutant strain MLK217 containing additional C_16:1 fatty acids.

^dΔM, mass difference between the observed and calculated mass of various lipid A species.