The effects on amylose conformation of percentage water in dimethyl su
lfoxide (DMSO)/water mixtures were measured by following changes in sp
ecific optical rotation, limiting viscosity number, and C-13-NMR chemi
cal shifts. The temperature dependence of specific optical rotation sh
owed differences in amylose conformation at four chosen ratios of dime
thyl sulfoxide/water. An amylose conformational change was also deduce
d from C-13-NMR chemical shift data. Changes in limiting viscosity of
amylose in different proportions of DMSO/water, and the effect of tetr
amethylurea on the specific rotation of amylose, indicate that intramo
lecular hydrogen bonding decreases with increased water content. 66.6%
DMSO appears to be a crossover concentration, below which the helical
conformation is progressively lost as water is added. When water cont
ent is over 60%, transition to a conformation which allows iodine comp
lexation to take place is complete. A transition of amylose conformati
on from helix to loose helix to random coil with increasing water cont
ent was deduced from the experimental results. (C) 1998 Elsevier Scien
ce Ltd. All rights reserved.