Molar mass and solution conformation of branched α(1 → 4), α(1 → 6) Glucans. Part I: Glycogens in water

Solution molar masses and conformations of glycogens from different sources (rabbit, oyster, mussel and bovine) were analysed using sedimentation velocity in the analytical ultracentrifuge, size-exclusion chromatography coupled to multi-angle laser light scattering (SEC-MALLS), size-exclusion chromatography coupled to a differential pressure viscometer and dynamic light scattering. Rabbit, oyster and mussel glycogens consisted of one population of high molar mass (weight averages ranging from 4.6 × 10⁶ to 1.1 × 10⁷ g/mol) as demonstrated by sedimentation velocity and SEC-MALLS, whereas bovine glycogen had a bimodal distribution of significantly lower molar mass (1.0 × 10⁵ and 4.5 × 10⁵ g/mol). The spherical structure of all glycogen molecules was demonstrated in the slopes of the Mark-Houwink-Kuhn-Sakurada-type power-law relations for sedimentation coefficient (s_20,w^o), intrinsic viscosity ([η]), radius of gyration (r_g,z) and radius of hydration (r_H,z), respectively, and was further supported by the ρ (=r_g,z/r_H,z) function, the fractal dimension and the Perrin function. The degree of branching was estimated to be ∼10% from the shrinking factors, g′ (=[η]_branched/[η]_linear) and also h (=(f/f_o)_branched/(f/f_o)_linear), respectively, where (f/f_o) is the translational frictional ratio, consistent with expectation.