MOLECULAR-SIZE ANALYSIS OF HAEMOPHILUS-INFLUENZAE TYPE-B CAPSULAR POLYSACCHARIDE

The molar mass and molar mass distribution of polyribosyl ribitol phos phate (PRP) was determined using high performance size-exclusion chrom atography with light scattering, viscometric, and refractive index det ection. Light scattering data showed the PRP preparations to have an M (w) of ca. 75,000, and a polydispersity (M(w)/M(n)) of about 1.46. Bas ed on integration of the molar mass and intrinsic viscosity data, the Mark-Houwink-Sakurada coefficients for PRP were determined to be a = 1 .45, and K = 3.57 x 10(-6) cm3/g for 0.2 M ammonium acetate pH 7.0, an d a = 1.54 and K = 0.6 x 10(-6) cm3/g for 0.1 M sodium phosphate, pH 7 .2. The values of a indicate that PRP is a rigid, rod-like molecule. T he rigidity of the PRP molecules is characterized by unperturbed dimen sions (<R(o)>/M1/2) of 0.24 nm in ammonium acetate buffer and 0.22 nm in sodium phosphate buffer. These results suggest that PRP likely has a highly ordered secondary structure.