Table 1.

Reconciliation of fatty acid composition of nonphosphorylated lipid A species recovered from P. gingivalis LPS^a

Precursor ion (recovered as a sodium adduct)	First deacylated ion massc	Resulting from loss of fatty acid (R1)	Loss of m/z 227 fragment from 3-OH C17:0d	Second deacylated ion masse	Resulting from loss of second fatty acid (R2)
m/z 1,364	m/z 1,120	3-OH C14:0	m/z 894	m/z 637	C16:0
	m/z 1,106	3-OH iso C15:0	m/z 880	m/z 637	Iso C15:0
	m/z 1,092	3-OH C16:0	m/z 866	m/z 637	C14:0
m/z 1,378	m/z 1,120	3-OH iso C15:0	m/z 894	m/z 637	C16:0
	m/z 1,106	3-OH C16:0	m/z 880	m/z 637	Iso C15:0
m/z 1,392	m/z 1,134	3-OH iso C15:0	m/z 908	m/z 637	Iso C17:0
	m/z 1,120b	3-OH C16:0	m/z 894b	m/z 637	C16:0
	m/z 1,106	3-OH iso C17:0	m/z 880	m/z 637	Iso C15:0
m/z 1,406	m/z 1,134	3-OH C16:0	m/z 908	m/z 637	Iso C17:0
	m/z 1,120	3-OH iso C17:0	m/z 894	m/z 637	C16:0

^aThe lipid A preparation of P. gingivalis was subjected to MALDI-MS/MS, and the observed ion fragments shown in Fig. 3 were used to reconcile the loss of fatty acids from these lipid A species. The listed precursor ions represent nonphosphorylated, tetra-acylated lipid A species that deacylate under MALDI-MS/MS in both the R1 and R2 positions with loss of the indicated fatty acids. Note that the second deacylation from the R2 position produces mostly one product ion for all precursor ions listed (m/z 637). Additional nonphosphorylated lipid A ions appear as sodium adducts, with masses of m/z 1,350, 1,336, and 1,322 (Fig. 2B). However, these lower-mass ions were recovered in low abundance, and MS/MS analysis was not feasible.

^bDominant ion transitions noted with MS/MS transitions (see Fig. 4B, C, and D).

^cSee Fig. 4B.

^dSee Fig. 4C.

^eSee Fig. 4D.