Optical rotation of some α‐1,4‐linked glucopyranosides in the system H2O–DMSO and solution conformation of amylose

The specific rotation of starch components, corrected for refractive index variation, exhibits a discontinuity in the region of the water–dimethyl sulfoxide (H2O–DMSO) system that corresponds to the composition of the complex 2H2O–DMSO. This discontinuity is a property dependent upon the presence of a number of consecutively linked α‐1,4 glucose units and, therefore, must reflect a change in symmetry of a segment, of polymer chain. The optical rotation of amylose between 26.5 and 92.5°C. does not change in DMSO and is only slightly lowered in water at the higher temperature. The behavior of amylose in both DMSO and H2O is like that of a random coil, as indicated by viscosity and sedimentation measurements. These results may be interpreted either as being compatible with models of amylose in solution in which the polymer backbone has helical twist, or as indicating removal of strong interactions between polymer chain segments by a good solvent.