Polysaccharide gels water molecules

Here T2 is the transverse relaxation time and D is the effective water-diffusion coefficient. In protein or polysaccharide solutions or gels there is fast exchange between water molecules in the bulk with those interacting with the macromolecule surface. There is also fast proton exchange between water and macromolecule protons. Both effects imply that D = /WZ)W + fsDs, where/w and/s are the water proton fractions in the bulk phase and surface respectively (/s +fw— 1) and Ds is the macromolecule diffusion coefficient. Since Ds < Z)w, the second term is negligible so that D = (1 -/S)Z)W. This predicts... 

Polyethylene oxides and amyloses (Mr > 4000) readily complex with polyphenols but quantitative studies have been severely limited by the availability of water-soluble polysaccharides with clearly defined molecular characteristics. Semi-quantitative studies show that the association of polyphenols with polysaccharides is - in contrast to that with proteins - broadly independent of pH. Molecular size and flexibility are likewise critical factors but, significantly, where the polysaccharide can sequester the hydrophobic aryl residues of the polyphenol - holes in a crystal lattice (cellulose) or hydrophobic cavities (amylose and polysaccharide gels) - then complexation is substantially enhanced. Open, flexible, filamentous polysaccharides, such as the l-a-6-dextrans conversely bind phenolic substrates very poorly. It is interesting to note that model polysaccharide holes - in the form of the a- and 3- cyclodextrins - can sequester the aryl residues of certain polyphenols in the core of the molecule. In doing... 

It has already been reported that the diermal stability of invertase improves upon enzyme concentration increase and inclusion fixation into PVA gel membrane [15]. Thermal stability improves upon fixation. Multifunctional alcohol also contributes to improvement in stability [11, 16]. The PVA is a kind of multifunctional alcohol and invertase is a typical polysaccharide having about a 50%-saccharide chain [17]. The thermal stability of the enzyme is probably improved by the stabilizing effect of the higher-order structure due to interaction between die hydroxyl groups and the water molecules included in the PVA and the polysaccharide chain. 

Curdlan gel formation is heat dependent. This polysaccharide is not soluble in water, but when an aqueous suspension is heated it becomes dear at about 54°C. Furdier heating leads to gel fonnation. The gels are stable over a wide range of pH (3 to 95) and do not melt at temperatures below 100°C. Curdlan gels are formed by cross-linldng, involvii conformational ordering of the exopolysaccharide molecules to give a triple helical structure. 

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