CHARACTERIZATION OF MENINGOCOCCAL POLYSACCHARIDES BY LIGHT-SCATTERING SPECTROSCOPY .4. MOLECULAR-WEIGHT DISTRIBUTION OF GROUP-B MENINGOCOCCAL POLYSACCHARIDE IN BUFFER SOLUTION

We report the first characterization of group B meningococcal polysaccharide at 28°C in 0.4M KCl and 0.05M sodium acetate at pH 5.61 and in pure water by means of light‐scattering spectroscopy. In buffer solution, the weight‐average molecular weight Mr = 1.46 × 105 g/mol, the Z‐average radius of gyration 〈rg2〉z1/2 = 26.3 nm, the second virial coefficient A2 = (2.12 ± 0.17) × 10−4 cm3 mol/g2, and the second virial coefficient of the diffusion expansion kD ≈ 79 g/g. By using a histogram approximation on the correlation function profile analysis, we observed size fractions of two sizes with rhL/rhS = 298 Å/50 Å and AL/AS = 82/18, where rh and A are the respective effective hydrodynamic radius and the integrated intensity and the subscripts L and S denote the large and small size fractions. In pure water, rhL/rhS = 402 Å/29 Å with AL/AS = 84/16. The linewidth results are consistent with the measurements on the angular distribution of scattered intensity. Furthermore, if we take the large fraction to behave more like solid spheres, we are able to determine a molecular weight distribution of B‐polysaccharide in buffer solution in a bimodal size distribution function. Copyright © 1979 John Wiley & Sons, Inc.