Molecular configuration of amylose and its complexes in aqueous solutions. Part III. Investigation of the DP distribution of helical segments in amylose–iodine complexes

Abstract

Abstract The equilibrium normality [I f ] of free iodine in amylose‐iodine complex formation is a function of the length of the polyiodine chains. This length depends on the DP of helical segments of amylose ( s DP n ). Values of [I f ] and of the concentration of the bound iodine [I b ] were determined by the continuous photometric titration with automatic recording. Plots of [I b ] versus [I f ] give an integral distribution curve. Since the relation between [I f ] and s DP n is known, the graphic differentiation of the [I b ] versus [l f ] curve furnishes the differential distribution curve, representing the mass distribution of the helical segments according to their DP . The peak of this curve is characteristic of the percentage and DP of those helical segments, which occur in the largest amount. On the basis of the differential distribution curve the polymolecularity of the investigated sample may be judged. The titration of amylose samples degraded by various methods gives different distribution curves. Titrating mixtures of samples with widely differing average DP values results in differential curves having more than one maximum.