The concentration dependence of sedimentation for polysaccharides

The relationship between the sedimentation coefficient s₀ and its concentration coefficient k_s obtained in experiments on velocity sedimentation for polysaccharides is discussed. The values of s₀, k_s and an independently determined molecular weight reported by different authors for different polysaccharides are considered. It was established that the scaling relation. k_s∼ s₀ ^v unambiguously relates to the scaling relation s₀∼ M^b. The values of the sedimentation parameter β _s introduced on the basis of Svedberg's equation for s₀ and on the basis of the expression k_s = B 〈h²〉^3/2M^–1 are discussed and the generalized Wales-van Holde-Rowe equation M_KS = (N_A/β _S)^3/2s]^3/2 k_S ^1/2 is used for evaluation of the molecular weights of polysaccharides. The adequacy of this evaluation is illustrated by taking as an example the determination of the unit length weight of an extra-rigid polysaccharide chain and of the equilibrium rigidity of rigid-chain, semi-rigid-chain and flexible-chain polysaccharides. The pair of experimental values s₀ and k_S obtained in a single series of experiments give the same information as may be obtained from the other pairs of hydrodynamic values such as η] and s₀ or η] and D₀, where η] is the intrinsic viscosity and D₀ is the translational diffusion coefficient. Accepted: 11 December 1996