Physicochemical Properties of the Vi Antigen Before and After Mild Alkaline Hydrolysis

Abstract

Sedimentation and diffusion constants were determined for electrophoretically purified Vi antigen before and after mild alkaline hydrolysis. The molecular weight of the intact antigen was found to be 1.7 x 10(6). Mild alkaline hydrolysis completely removed O-acetyl, reduced the molecular weight to 1.0 x 10(5), and lowered the intrinsic viscosity from 8.0 deciliters/g to approximately 0.5 deciliter/g. Infrared spectra of the two antigen preparations were also compared.