title: Ultrastructural evidence for intramolecular double stranding in iota-carrageenan.
abstract: Kinetic studies of primary processes of conformational ordering in gel-forming biopolymers have suggested that a change in mechanism from intermolecular to intramolecular multistrand formation occurs on lowering the concentration of biopolymer. We report here ultrastructural observations consistent with intramolecular double stranding in a carbohydrate polymer, iota-carrageenan, by arresting this process of primary conformational ordering by an ultra-rapid freeze fixation technique. High-resolution transmission electron microscopy (TEM) revealed isolated iota-carrageenan chains showing a range of morphologies (linear, circular, and hairpin) consistent with intramolecular stranding. Control experiments in which iota-carrageenan was frozen in the disordered form revealed longer and thinner strands.
authors.affiliation: Institute for Applied Biology, University of York, Heslington, United Kingdom.
authors.forename: R M
authors.initials: RM
authors.lastname: Abeysekera
authors.forename: E T
authors.initials: ET
authors.lastname: Bergström
authors.forename: D M
authors.initials: DM
authors.lastname: Goodall
authors.forename: I T
authors.initials: IT
authors.lastname: Norton
authors.forename: A W
authors.initials: AW
authors.lastname: Robards
mesh_terms: D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002351:Carrageenan / Q000737:chemistry*; D004187:Disaccharides / Q000737:chemistry; D008854:Microscopy, Electron / Q000379:methods; D008969:Molecular Sequence Data
chemical_list: D004187:Disaccharides; D002351:Carrageenan