Measurement of diffusion coefficients of meningococcal polysaccharide by optical mixing spectroscopy. I. A preliminary characterization on the aggregation of the Group C polysaccharide

The angular distribution of scattered intensity and decay times of concentration fluctuations have been measured by means of digital photon counting and single‐clipped photon correlation for solutions of Group C meningococcal polysaccharides at 31°C. The z ‐average diffusion coefficient 〈 D 〉 z and its second moment 〈 D 2 〉 z have been determined from the time‐dependent correlation function using the cumulant expansion technique. Very low observed values of 〈 D 〉 z and the tremendous width of the polydispersity index, which is the z ‐average normalized variance, suggest a higher degree of aggregation than the monomer–dimer type self‐association at finite concentrations.