VACUUM-ULTRAVIOLET CIRCULAR-DICHROISM OF GELLAN-FAMILY POLYMER-FILMS FROM WATER AND DIMETHYL-SULFOXIDE

The denaturing effect of dimethyl sulfoxide (Me(2)SO) on the conformat ion of the gellan-welan-rhamsan family of microbial polysaccharides is directly demonstrated by circular dichroism (CD). The three polysacch arides display strikingly similar CD spectra (140-210 nm) for films ca st from Me(2)SO. The disrupting effect of Me(2)SO on gellan and welan conformations has previously been reported by others on the basis of l ight-scattering and viscosity studies. Films cast from aqueous solutio ns at room temperature show more-intense CD bands, both at 182 nm, as is also observed for aqueous solutions, and in the 150-175 nm region. These features correspond to the ordered helical chains found by X-ray diffraction studies of similarly prepared films.