STUDIES ON A LIPOPOLYSACCHARIDE FROM ESCHERICHIA COLI . HETEROGENEITY AND MECHANISM OF REVERSIBLE INACTIVATION BY SODIUM DEOXYCHOLATE

A lipopolysaccharide from Escherichia coli K-235 contains free amino groups which can be converted into the 2,4-dinitrophenylamino groups without loss of pyrogenicity. This derivative permitted study of its reversible disaggregation and inactivation by sodium deoxycholate at low concentrations of both solutes; 99 % inactivation of pyrogenicity required at least 1 mg of sodium deoxycholate/ml and was accompanied by 100% disaggregation of 2,4-dinitrophenylaminolipopolysaccharide to a subunit of 118,000 daltons. The same degree of disaggregation to the same size of subunit was also obtained without any decrease in pyrogenicity in solutions of 0.02 and 0.03 mg of sodium deoxycholate per ml. Regardless of the sodium deoxycholate concentration 100% disaggregation required a sodium deoxycholate:2,4-dinitrophenylaminolipopolysaccharide ratio of only 4:6, but 0.03 mg of sodium deoxycholate/ml failed to depress pyrogenicity even though the sodium deoxycholate:2,4-dinitrophenylaminolipopolysaccharide ratio was 3000. Inactivation of 2,4-dinitrophenylaminolipopolysaccharide therefore probably depends upon an interaction with sodium deoxycholate beyond that which is required for disaggregation. Gel permeation chromatography in sodium deoxycholate solution indicated that lipopolysaccharide is a heterogeneous population of closely related molecules which are all highly pyrogenic. © 1969, American Chemical Society. All rights reserved.