Salmonella free lipid

When this method, in a slightly modified form, was applied to Salmonella free lipid A, mainly two compounds were liberated which were detected by gas-liquid chromatography and characterized by mass spectrometry. The spectrum of the first compound was identical with that of authentic 3-hydroxytetradecanoic acid, 3-0-acylated by dodecanoic acid (3-0-dodecanoyl-tetradecanoic acid methyl ester, 3-0(12 0)-14 0) (27). The mass spectrum of the second peak showed, inter alia, characteristic fragments at 496 (M ), 465 (M-31), 239, 240 and 241, thus corresponding to 3-0-hexadecanoyl-tetradecanoic acid methyl ester (3—0(16 0)—14 0). Therefore, the two components present in Salmonella lipid A in amide linkage and released by the above described procedure... 

Of the lipid portions of bacterial macromolecular amphiphi-les, that of lipopolysaccharides is the structurally most complex. For its designation the term lipid A has been coined. More specifically, it was suggested that the lipid, as it is present in intact lipopolysaccharide, should be called lipid A, while the lipid in a separated form should be termed free lipid A (10,11). This nomenclature will be used throughout this paper. In the following, ways and methods will be described which have been used to elucidate the chemical structure of lipid A. The present discussion will deal in more detail with the elucidation of the structure of Salmonella lipid A. Relative to this structure, chemical features of other lipid A s will then be discussed. 

Total fatty acids were liberated by subjecting Salmonella minnesota Re lipopolysaccharide (or free lipid A) to acidic (4 N HC1, 5 h, 100°C) followed by alkaline (1 N NaOH, 1 h, 100°C) hydrolysis. After extraction (chloroform), the free fatty acids were converted into their methyl esters (diazomethane) and analysed by combined gas-liquid chromatography/mass spectrometry. Alternatively, the fatty acids of lipid A are transesterified by treatment of lipopolysaccharide with methanolic HC1 (2 N HC1 in water-free CHaOH, 18 h, 85°C). By these procedures the following fatty acids were identified (in approximate amounts relative to 2 moles glucosamine) dodecanoic (12 0, 1.1 mole), tetradecanoic (14 0, 0.8 mole), hexadecanoic (16 0, 0.9 mole), 2-hydroxytetradecanoic (2-OH-l4 0, 0.1 mole), and 3-hydroxytetradecanoic acid (3-OH-14 0, 4 moles). In total, therefore, approximately 7 moles of fatty acids are present per mole of lipid A backbone. The stereochemistry of the hydroxylated fatty acids was determined by gas-liquid chromatography of their diastereomeric methoxyacyl-L-phenylethylamide derivatives (24). It was found that 2-hydroxyte-tradecanoic acid possesses the-Ts), and the predominating 3-hydroxytetradecanoic acid the (R) configuration. 

Brandenburg, K. Fourier transform infrared spectroscopy characterization of the lamellar and non-lamellar structures of free lipid A and Re lipopolysaccharides from Salmonella Minnesota and Escherichia coli. Biophys J 64 (1993) 1215-1231. 

Free lipid A was isolated by acetate buffer treatment of lipopolysaccharide from Salmonella minnesota strain R595. After isolation, the resulting lipid A... 

Using PTLC six major fractions of lipids (phospholipids, free sterols, free fatty acids, triacylglycerols, methyl esters, and sterol esters) were separated from the skin lipids of chicken to smdy the penetration responses of Schistosoma cercaria and Austrobilharzia variglandis [79a]. To determine the structure of nontoxic lipids in lipopolysaccharides of Salmonella typhimurium, monophosphoryl lipids were separated from these lipids using PTLC. The separated fractions were used in FAB-MS to determine [3-hydroxymyristic acid, lauric acid, and 3-hydroxymyristic acids [79b]. 

C A from pig intestine and Lipid A (LA) from Escherichia coli (L A-E) and Salmonella minnesota (LA-S) were obtained from Sigma Chemical Co. (St. Louis, MO). LPS (MW, 10,000 g mole ) was prepared from Pantoea agglomerans (ATCC 27996) as described earlier (De Lucca et al., 1992). All other chemicals were reagent grade. Water and laboratory-ware were pyrogen-free. 

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