ISSN:
1435-1528
Source:
Springer Online Journal Archives 1860-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
Summary The amylose molecule is extended by the insertion of iodine in quantities up to a ratio of one molecule per turn of the helix. Ordinary cornstarch and its amylopectin fraction do not respond in the same manner. As the iodine content was increased the intrinsic viscosity [η] rose from 0.55 to 1.45 dl/g, then remained constant. In this same range theHuggins' interaction parameterk′ for the dependence of reduced viscosity [η sp/C] on iodine concentration rose from 0.31 to 5.65 and continued to increase. Reduction ofd[η]/dT by complexing from −0.36 × 10−2 to −0.23 × 10−2 dl/g/deg provided an independent measure of the flexibility of the molecule and revealed that iodine stiffens the helix in some manner. The dipolar interaction between iodine and the helix restricts conformational changes and increases the average extension. As more iodine molecules enter the helical chain the average distribution of molecular segments relative to the center of mass of the molecule spreads outward.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01527068
