Rheology and microstructure of solutions of the microbial polysaccharide from Pseudomonas elodea

Rheological studies of solutions and gels of the microbial polysaccharide from the organism Pseudomonas elodea have been combined with X-ray diffraction studies of fibres and pulsed electric-birefringence studies of dilute solutions, to investigate the conformation and interaction of the polymer molecules. Rheological data are suggestive of a locally rigid conformation for the biopolymer in solution. X-Ray diffraction studies suggest that the molecules adopt a three-fold helical structure. O-Acetyl substituents have been shown to inhibit the packing of these helices into crystalline domains. Studies of pulsed electric-birefringence suggest an extended, kinetically rigid structure in solution. Dissolving the polysaccharide in dimethyl sulphoxide inhibits the gelation and shear-thinning characteristics of aqueous solutions. Comparative studies of electric birefringence of solutions in water and dimethyl sulphoxide suggest that the differences in rheological properties may result from a change in molecular conformation.