title: Nature of alpha and beta particles in glycogen using molecular size distributions.
abstract: Glycogen is a randomly hyperbranched glucose polymer. Complex branched polymers have two structural levels: individual branches and the way these branches are linked. Liver glycogen has a third level: supramolecular clusters of beta particles which form larger clusters of alpha particles. Size distributions of native glycogen were characterized using size exclusion chromatography (SEC) to find the number and weight distributions and the size dependences of the number- and weight-average masses. These were fitted to two distinct randomly joined reference structures, constructed by random attachment of individual branches and as random aggregates of beta particles. The z-average size of the alpha particles in dimethylsulfoxide does not change significantly with high concentrations of LiBr, a solvent system that would disrupt hydrogen bonding. These data reveal that the beta particles are covalently bonded to form alpha particles through a hitherto unsuspected enzyme process, operative in the liver on particles above a certain size range.
authors.affiliation: Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Victoria, Australia.
authors.forename: Mitchell A
authors.initials: MA
authors.lastname: Sullivan
authors.forename: Francisco
authors.initials: F
authors.lastname: Vilaplana
authors.forename: Richard A
authors.initials: RA
authors.lastname: Cave
authors.forename: David
authors.initials: D
authors.lastname: Stapleton
authors.forename: Angus A
authors.initials: AA
authors.lastname: Gray-Weale
authors.forename: Robert G
authors.initials: RG
authors.lastname: Gilbert
mesh_terms: D000818:Animals; D002850:Chromatography, Gel; D006860:Hydrogen Bonding; D008099:Liver / Q000378:metabolism* / Q000648:ultrastructure; D008112:Liver Glycogen / Q000737:chemistry*; D008970:Molecular Weight; D010316:Particle Size; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D008112:Liver Glycogen