CF-252 PLASMA DESORPTION MASS-SPECTROMETRY APPLIED TO THE ANALYSIS OFUNDERIVATIZED ROUGH-TYPE ENDOTOXIN PREPARATIONS

Plasma desorption mass spectrometry has recently been used with succes s to characterize native, underivatized Re- to Rc-type endotoxins in t erms of their constituent lipopolysaccharides. The spectra give masses for the major molecular species of lipopolysaccharide present from wh ich their probable compositions could be inferred using the overall co mposition determined by chemical analyses. Moreover, the relative inte nsities of the signals are roughly proportional to the abundance of th eir corresponding molecular species. Native Rc-, Rb-, and Ra-type ente robacterial endotoxins with 5-10 core sugar units have been rendered a menable to plasma-desorption mass spectrometry analysis by improvement in their solubility and the use of cellobiose as an additive. The spe ctra of four Salmonella and Escherichia endotoxin preparations demonst rated heterogeneity in acylation and phosphorylation. Since these sour ces of heterogeneity are critical for many biological activities, the spectra underline the need to define the composition of each preparati on of endotoxin used in structure-function studies.