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

Abstract

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 × 10 6 to 1.1 × 10 7 g/mol) as demonstrated by sedimentation velocity and SEC-MALLS, whereas bovine glycogen had a bimodal distribution of significantly lower molar mass (1.0 × 10 5 and 4.5 × 10 5 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.