The dispersion of gram-negative lipopolysaccharide by deoxycholate. Subunit molecular weight.

The lipopolysaccharide (LPS) was isolated from three strains of Salmonella typhimurium, a "smooth" strain, STM 7, the Ra mutant, TV 119, and the Re mutant, SL 1102. The effect of depletion of divalent cations on structure and the effect of deoxycholate on hydrodynamic behavior were studied. The results confirmed previous work by others that divalent cations and hydrophobic forces are important factors influencing LPS size and morphology. The binding of deoxycholate to LPS was measured. When the weight average molecular weights of the deoxycholate-dissociated LPS were determined by sedimentation equilibrium and corrected for bound deoxycholate, the values 5,555, 10,607, and 15,592, respectively, for Re, Ra, and "smooth" LPS were in good agreement with calculated formula weights. Although others have suggested that the basic LPS subunit is a trimer, our results suggest that it exists in the dimeric form.