ANALYSIS BY CF-252 PLASMA DESORPTION MASS-SPECTROMETRY OF BORDETELLA-PERTUSSIS ENDOTOXIN AFTER NITROUS DEAMINATION

Endotoxic lipopolysaccharides (LPSs) are the major components of Gram- negative bacterial outer membrane. Like many amphipathic molecules, th ey pose problems of heterogeneity, purity, solubility, and aggregation . Nevertheless, PDMS has recently been applied to unmodified endotoxin s composed of LPS having up to five sugar units in their saccharide ch ain. The B. pertussis LPSs, most of which have a dodecasaccharide doma in, have been analysed by classical methods and the masses of the sepa rate lipid and saccharide domains determined after rupture of the bond linking them. However, the acid treatment employed for these and most chemical analyses can also modify structures in the vicinity of the b ond. In order to investigate this biologically-important region, the e ndotoxin was treated to nitrous deamination, which shortens the saccha ride chain to five sugars, but preserves the acid-labile region of the LPS. The PDM spectrum of this derivative, which required new conditio ns for its desorprtion, confirmed the structure analysis and demonstra ted the presence of at least four molecular species.