Triple helix of Schizophyllum commune polysaccharide in dilute solution. 5. Light scattering and refractometry in mixtures of water and dimethyl sulfoxide

Abstract

Light scattering and differential refractive index measurements were made on a sonicated sample of schizophyllan in water + dimethyl sulfoxide (Me2SO) mixtures over the entire composition range at 25 °C. When the water composition was diminished to about 13 wt %, the weight-average molecular weight Mw and the z-average mean-square radius of gyration (S2)z were found to decrease abruptly to the values in pure Me2SO. This result directly checks the previous deduction from viscosity data that the triple helix of schizophyllan would dissociate to single randomly coiled chains at a water composition of about 13 wt %. Analysis of the Mw and (S2)z data indicated that the dissociation proceeds in all-or-none fashion. Specific refractive index increments for dialyzed and undialyzed solutions showed that the Me2SO molecule adsorbs preferentially on schizophyllan in the region of water composition below about 40 wt %.

Conformational transitions of schizophyllan in aqueous alkaline solution

“…Increase in AH,,, is possibly due to preferential solvation of schizophyllan by DMS0. 30 The present data obtained for KOH solutions show that AH,,, does not decrease with increasing pH, but the decrease ofthe cooperative unit size is due to decreasing AHvH. In other words, the areas under the peaks in Figure 1 are unchanged, but the peak widths are increasing.…”

Double-Stranded Helix of Xanthan in Dilute Solution: Evidence from Light Scattering

“…The dialysis was effected using Visking gel-cellophane membranes and the dialyzer described elsewhere. 25 The values of (8nj8c) 11 obtained were 0.144 and 0.141 cm 3 g-1 for 436 and 546nm, respectively. The former agreed with Paradossi-Brant's value 15 of 0.144 cm 3 g-1 for the same system at 27°C.…”

Chain Stiffness and Excluded-Volume Effects in Polyelectrolyte Solutions: Characterization of Sodium Poly(2-acrylamido-2-methylpropanesulfonate) in Aqueous Sodium Chloride

“…Based on these findings, 0.05 and 0.5 M aqueous NaCl solutions of the sample with M v ¼ 10 5 were dialyzed against the corresponding solvents at 25 C using the previously described apparatus. 21 The ð@n=@cÞ values obtained for the dialyzed solutions (i.e., at fixed chemical potentials of diffusible components) at 25 C were 0.146 and 0.143 cm 3 g À1 at C s ¼ 0:05 M for 436 and 546 nm, respectively, and 0.141 and 0.139 cm 3 g…”