Ultrastructural evidence for intramolecular double stranding in iota-carrageenan.
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.
Abeysekera
R M
RM
Institute for Applied Biology, University of York, Heslington, United Kingdom.
Bergström
E T
ET
Goodall
D M
DM
Norton
I T
IT
Robards
A W
AW
D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D002351:Carrageenan / Q000737:chemistry*; D004187:Disaccharides / Q000737:chemistry; D008854:Microscopy, Electron / Q000379:methods; D008969:Molecular Sequence Data
D004187:Disaccharides; D002351:Carrageenan