AMYLOSE CONFORMATIONAL TRANSITIONS IN BINARY DMSO WATER MIXTURES/

The effects of percentage water content in DMSO/water mixtures on amyl ose conformation were measured by following changes in specific optica l rotation,limiting viscosity number, and C-13-NMR chemical shifts. Th e temperature dependence of specific optical rotation showed differenc es in amylose conformation for four ratios of dimethyl suphoxide/water . The changes in limiting viscosity of amylose in different proportion s of DMSO/water with increasing temperature, and the effect of tetrame thylurea on the specific rotation of amylose, indicate that the number of intramolecular hydrogen bonds decreases with increased water conte nt. An amylose conformational change was also deduced from C-13-NMR ch emical shift changes. Thirty-three percent water appears to be a cross over concentration, above which the helical conformation is progressiv ely lost with increased temperature. With further increase in water co ntent to 66.6%, transition to a random coil conformation is complete, and iodine complexation may take place. The transition of amylose conf ormation from helix to loose helix to random coil with increasing wate r content was deduced from the experimental results.