Hydrodynamic properties and dimensions of linear potato amylose molecules in dilute aqueous salt solution

Abstract

AbstractViscometric, sedimentation and lightscattering measurements have been carried out on five fractions of amylose in 0.33 M aqueous potassium chloride to obtain weight‐average molecular weights M̄w and configurational parameters. The amylose fractions were obtained from the subfractionation of natural amylose and were shown by enzymic experiments to be completely linear. The range of molecular weight investigated was from 1.6·105 to 22.9·105. The following empirical relations have been obtained for the limiting viscosity number, [η], and the sedimentation coefficient at infinite dilution, S0: [η] = 1.12·10−3 M̄w0,50 and S0 = 1.11·10−15 M̄w0,50. The value of the exponent in both equations indicated that amylose behaves as a random coil in 0.33 M potassium chloride in agreement with the results of EVERETT and FOSTER1). Calculations have been made of the unperturbed dimensions of amylose in this solvent, and there was no evidence of stiffening of the molecule with decreasing chain‐length for the molecular weight range studied. The lightscattering measurements indicated that aqueous potassium chloride was behaving as a thermodynamically ideal solvent.Mean square end‐to‐end distances from the lightscattering measurements have ben compared with values calculated from current theories of the hydrodynamic behaviour of dilute polymer solutions.