Lipopolysaccharides from Escherichia coli O55:B5

Lipopolysaccharides (LPSs) are characteristic components of the cell wall of Gram-negative bacteria. LPS and its lipid A moiety stimulate cells of the innate immune system by the Toll-like receptor 4 (TLR4), a member of the Toll-like receptor protein family, which recognizes common pathogen-associated molecular-patterns (PAMPs).

Lipopolysaccharides (LPS) are localized in the outer layer of the membrane and are, in noncapsulated strains, exposed on the cell surface. They contribute to the integrity of the outer membrane, and protect the cell against the action of bile salts and lipophilic antibiotics.

This product is extracted from E. coli serotype O55:B5 and purified by gel filtration. The source strain is CDC 1644-70. The LPS O55:B5 has been used to stimulate human peritoneal macrophages at 1 ng/ml and to stimulate equine peritoneal macrophages at 1-100 ng/ml.

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The product is soluble in water (5 mg/ml) or cell culture medium (1 mg/ml) yielding a hazy, faint yellow solution. A more concentrated, though still hazy, solution (20 mg/ml) has been achieved in aqueous saline after vortexing and warming to 70-80 ^oC. Lipopolysaccharides are molecules that form micelles in every solvent. Hazy solutions are observed in water and phosphate buffered saline. Organic solvents do not give clearer solutions. Methanol yields a turbid suspension with floaters, while water yields a homogeneously hazy solution.