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. 2003 Jul 10;100(15):8898–8903. doi: 10.1073/pnas.1432026100

Fig. 4.

Fig. 4.

Negative ion CE-ESI-MS shows major glycoforms of LPS-OH extracted from NTHi strain 486. (A) Extracted mass spectrum for LPS-OH extracted from NTHi bacteria used to inoculate chinchillas. The mass spectrum is dominated by molecular peaks corresponding to doubly [(M-2H)2–] and triply [(M-3H)3–] charged ions. Triply charged ions at m/z 921 and 962 represent the lactose containing glycoform populations comprising four hexoses (Fig. 3A: R1 = H; R2 = phosphocholine residue-6Glc; R3 = lactose). The glycoform responsible for the ion at m/z 921 has a phosphate group at O-4 of the KDO residue, whereas that at m/z 962 carries a PPEtn group (Fig. 3A). Related doubly charged ions at m/z 1,382 and 1,444 are also observed. (B and C) Extracted mass spectra obtained from the CE-ESI-MS of exudate from the ear of a chinchilla 4 and 6 days, respectively, after inoculation with 50 WT organisms of the NTHi strain 486 described in A. In addition to ions corresponding to the Hex4 glycoforms observed in A, sialyllactose containing LPS species from the KDO-phosphate series of glycoforms are observed at m/z 764 [(M-4H)4–], 1,018 [(M-3H)3–], and 1,527 [(M-2H)2–] in B. After 6 days, ions due to the sialylated glycoforms (e.g., m/z 1,018) are only just detectable above background (C).