Fractions of lipopolysaccharide from Escherichia coli O111:B4 prepared by two extraction procedures

Lipopolysaccharides have been extracted from Escherichia coli O111:B4 by phenol extraction and by a new method employing aqueous butanol. Both methods yield very similar lipopolysaccharide preparations. Gel filtration chromatography of either preparation yields two physically and chemically distinct lipopolysaccharide fractions. One fraction contains lipopolysaccharide molecules with long antigenic side chains. It acts like a highly asymmetric unit with an apparent weight of 1.5 times 10-6 and is not dissociated by detergents or deacylation. The second fraction has a short antigenic side chain and can be dissociated by sodium dodecyl sulfate and Triton X-100 into units of approximately 90,000. Some properties of the lipopolysaccharide fractions vary with the method of extraction.