VISCOSITY AND SEDIMENTATION STUDIES ON AMYLOSE IN AQUEOUS SOLUTION - FURTHER EVIDENCE FOR NON-HELICAL CHARACTER

Viscosity and sedimentation measurements have been carried out on subfractions of native amylose dissolved in a thermodynamically ideal solvent (0·33 M KCl) and a good solvent (0·2 M KOH). The relations: [n{long right leg}]KC1 = 1·12 x 10-1MW0.50; [n{long right leg}]KOH = 6·92 x 10-3MW0.78;(S0)KC1 = 1·11 x 10-15MW0.50; (S0)SOH = 2·73 x 10-15MW0.41; were obtained. The divergence of the exponents from a value of 0·50 for the measurements in KOH is shown to be due to expansion of the molecule through solvent-polymer interaction rather than to partial free-draining character. The unperturbed dimensions of amylose were found to be the same in both solvents, on the basis of the Burchard-Stockmayer-Fixman and the Cowie-Bywater treatments. Measures of 'molecular stiffness' were obtained (Kuhn-Kuhn and Hearst-Stockmayer theories) on the basis of different molecular models including that of the 'interrupted helix'. The latter model appears to be incorrect: analysis of the hydrodynamic data shows that the amylose molecule in aqueous solution is best regarded as a fairly flexible coil. © 1969.