Urea/NaOH aqueous solution as new solvent of aeromonas gum

Aeromonas (A) gum, an acidic heteropolysaccharide, formed aggregates easily in NaCl aqueous solution. A novel solvent of the A gum, which can prevent aggregation, was found to be 0.20M urea/0.25M NaOH aqueous solution. The weight-average molecular weight (Mw), radius of gyration (1/2), and intrinsic viscosity ([(eta)]) of the samples were determined in 0.20M urea/0.25M NaOH aqueous solution at 25 (degree) C by light scattering (Mw, 1/2) and viscometry ([(eta)]). The values of Mw, 1/2, and [(eta)] were close to those in 0.20M lithium chloride/dimethylsulfoxide, in which the A gum exists as a semiflexible single chain, implying the same conformation for the A gum in 0.20M urea/0.25M NaOH aqueous solution. The results revealed that 0.20M urea/0.25M NaOH aqueous solution is a good solvent, which effectively avoids the aggregates of the A gum in aqueous solution. Moreover, it can be used to investigate the solution properties and chain conformation of water-insoluble polysaccharides or the polysaccharides that are easily aggregated in aqueous systems.