Abstract
The effect of sonication on the particle size of lipopolysaccharide (LPS) in aqueous media was studied, in order to examine the relation of particle size to pyrogenicity in rabbits, by the sucrose density gradient ultracentrifugation technique. LPS extracted from E. coli UKT-B according to the phenol/water method showed a polydispersed profile on the gradients, but after sonication for 3 min it formed a single peak in the lower density regions. From the results of electron micrographic observations, partial specific volume, viscosity and turbidity measurements, and density gradient data, it was revealed that sonication produced a decrease in the particle size of LPS. A more marked pyrogenicity in rabbits was observed in the LPS fractions in the lower density regions than in the higher ones, or in the fractions having smaller-sized particles of LPS than in the fractions having larger particles.
