COMPARISON OF LIPIDS A OF SEVERAL SALMONELLA AND ESCHERICHIA STRAINS BY CF-252 PLASMA DESORPTION MASS-SPECTROMETRY

Plasma desorption mass spectrometry has recently been used with succes s to characterize underivatized lipid A preparations: the major molecu lar species present give signals indicating their masses, from which p robable compositions could be inferred by using the overall compositio n determined by chemical analyses. In the present study, plasma desorp tion mass spectrometry was used to compare structures in lipid A prepa rations isolated from several smooth and rough strains of Escherichia and Salmonella species. Preparations isolated from strains of both gen era revealed considerable variation in degree of heterogeneity (number of fatty acids and presence or absence of hexadecanoic acid, phosphor ylethanolamine, and aminoarabinose). Molecular species usually associa ted with Salmonella lipid A were found in preparations from Escherichi a sp. In addition, preparations from three different batches of lipid A from one strain of Salmonella minnesota showed significant differenc es in composition. These results demonstrate that preparations used fo r biological and structural analyses should be defined in terms of the ir particular molecular constituents and that no generalizations based on analysis of a single preparation should be made.