title: An analytical ultracentrifugation based study on the conformation of lambda carrageenan in aqueous solution.
abstract: The conformation and heterogeneity of lambda-carrageenan, a sulphonated galactan from red seaweed, solubilised in aqueous solvent with the assistance of microwave irradiation, has been assessed by a combination of analytical ultracentrifugation, size-exclusion chromatography, light scattering and capillary viscometry. Preparations appeared generally unimodal on the basis of sedimentation coefficient distributions from sedimentation velocity although at the highest concentrations a shoulder appears with a sedimentation coefficient approximately 1.1 times greater than that of the main component. Even under conditions commensurate with charge suppression simple linear regression was insufficient to represent non-ideal concentration dependence and the extraction of the Grálen concentration dependence parameter ks. A more general fitting algorithm was therefore employed. Mark-Houwink-Kuhn-Sakurada analysis of the change in intrinsic viscosity [η] with molecular weight, together with the Wales-van Holde ratio (combination of ks with [η]) point to an extended flexible conformation for lambda-carrageenan in the (weight average) molecular weight range Mw=340,000-870,000g/mol. The origin of the larger sedimentation coefficient component appearing at the higher concentrations is considered.
authors.affiliation: National Centre for Macromolecular Hydrodynamics, University of Nottingham, Sutton Bonington LE12 5RD, UK.
authors.forename: Fahad M
authors.initials: FM
authors.lastname: Almutairi
authors.forename: Gary G
authors.initials: GG
authors.lastname: Adams
authors.forename: Mehmet S
authors.initials: MS
authors.lastname: Kök
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Lawson
authors.forename: Roland
authors.initials: R
authors.lastname: Gahler
authors.forename: Simon
authors.initials: S
authors.lastname: Wood
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Foster
authors.forename: Arthur J
authors.initials: AJ
authors.lastname: Rowe
authors.forename: Stephen E
authors.initials: SE
authors.lastname: Harding