title: Elucidation of gelation mechanism and molecular interactions of agarose in solution by 1H NMR.
abstract: Many biopolymers assume ordered structure in solution due to specific intermolecular interactions, and subsequently aggregate to form fibrous network structures, which play important structural and functional roles both in biomedical tissues and in biopolymeric applied materials. In this study, the pulsed-field-gradient stimulated echo (PGSTE) (1)H NMR method was utilized to elucidate the gelation mechanism and to determine the network structure of agarose. The echo signal intensity of agarose decreased with the formation of aggregated bundles, and therefore, it was used to determine the concentration of the solute agarose (c(sol)) in the gel. The diffusion coefficient of a dendrimer, added to the gel as a probe molecule, increased concomitantly with the formation of the network of aggregated bundles, suggesting apparent dilution of solute agarose in the network interspaces. The hydrodynamic mesh size (ξ) of the network was estimated from the degree of retardation of the diffusion. The dependence of ξ on c(sol) was interpreted using a simple model, where the hydrodynamic interaction of the probe molecule with a solute chain or an aggregated bundle of chains is same. Our theoretically predicted lines fitted well on the experimentally obtained plots, thus validating the use of this model.
authors.affiliation: Department of Food Science and Technology, Tokyo University of Marine Science and Technology, 4-5-7 Konan, Tokyo 108-8477, Japan.
authors.forename: Bona
authors.initials: B
authors.lastname: Dai
authors.forename: Shingo
authors.initials: S
authors.lastname: Matsukawa
mesh_terms: D001704:Biopolymers / Q000737:chemistry; D004058:Diffusion; D005782:Gels / Q000737:chemistry; D057446:Hydrodynamics; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D015394:Molecular Structure; D044367:Phase Transition; D012685:Sepharose / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D044366:Transition Temperature
chemical_list: D001704:Biopolymers; D005782:Gels; D012996:Solutions; D012685:Sepharose