SynopsisGroup-specific polysaccharides isolated by means of a cetavlon procedure are immunogenic in man and induce protective immunity against meningococcal meningitis. Minute quantities of the polymers in solution can act as vaccines. We now report the first characterization of a fractionated (C-1) group C polysaccharide in 0.4M KC1 and 0.05M sodium acetate by means of light-scattering spectroscopy. Independent measurements of refractive index increments, absolute scattered intensities, angular scattering intensities and line widths as a function of scattering angles and delay times a t different concentrations using incident wavelengths of 632.8 nm from a He-Ne laser and of 488 nm from an argon-ion laser yield information on aggregation properties, molecular weight ( M r ) , radius of gyration ( r i ) t", translational diffusion coefficient (D):, and second virial coefficients A2 and B2 of C-1 polysaccharide.At relatively high ionic strength (0.4M KCI + 0.05M sodium acetate), we obtain for the C-1 polysaccharide in solution M, = 5.15 X lO5;(ri);" = 345 A, A2 = 1.25 X ml/g, ( 0 ) ; = 1.16 X cm2/sec with a corresponding Stokes radius of 240 A and B2 = 4.4 ml/g. A2and Bz are the second virial coefficients from intensity-and diffusion-coefficient measurements. The C-1 polysaccharide aggregates in solution and behaves hydrodynamically like random coils: Viscosity and sedimentation studies further confirm our conclusions that the fractionated C-1 polysaccharide aggregates in solution and EDTA can partially break up those aggregates. However, the system remains polydisperse even after adding an excess amount of EDTA. The weight-average molecular weight of the C-1 polysaccharide in solution depends upon ionic strength and exhibits a minimum a t 4 . 2 M KCI. Finally, viscosity, light-scattering, and sedimentation results all show that the aggregated macromolecular system behaves like random-coiled polymers with no measurable shape factors.

The depo1arized light scattering spectrum from a dynamic. continuous chain model of a macromolecule in ~olution is calculated. For vanishing chain "stiffness" the results reduce to those predicted by Ono and Okano for the Rouse-Zimm model. For intermediate degrees of stiffness the contribution of the longer wavelength modes to the spectrum is enhanced. 3254

The depolarized light scattering spectrum from a dynamic, freely rotating chain model of a macromolecule is calculated. The previous theory is improved to include a chain stiffness parameter which is related to the persistence length of the polymer chain and hence can be measured by other experimental techniques. In the flexible limit of the model the results reduce to those by Ono and Okano for the Rouse–Zimm model. For intermediate degrees of chain stiffness the contribution from the lowest mode to the scattering intensity is enhanced.

Initial relaxation times determined by the initial decay rate of the time correlation function of scattered light are calculated for the once‐broken rod model (two rigid rods of equal length connected by a universal joint) following the Fujiwara–Saito theory. The coefficient C describing the initial angular dependence of the first cumulant of the correlation function is also calculated. The results are compared with Pecora's results based on the Yu–Stockmayer theory for this model; and it is shown that the Fujiwara–Saito theory gives reasonable results.