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    An analytical ultracentrifugation based study on the conformation of lambda carrageenan in aqueous solution
    (Elsevier Sci Ltd, 2013) Almutairi, Fahad M.; Adams, Gary G.; Kök, Mehmet Şamil; Lawson, Christopher J.; Gahler, Roland
    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 Gralen concentration dependence parameter k(s). A more general fitting algorithm was therefore employed. Mark-Houwink-Kuhn-Sakurada analysis of the change in intrinsic viscosity [eta] with molecular weight, together with the Wales-van Holde ratio (combination of k(s), with [eta]) point to an extended flexible conformation for lambda-carrageenan in the (weight average) molecular weight range M-w = 340,000-870,000 g/mol. The origin of the larger sedimentation coefficient component appearing at the higher concentrations is considered. (C) 2013 Elsevier Ltd. All rights reserved.