Calculated molecular weight distribution for glutenin

The size distribution of linear glutenin molecules has been calculated using standard theory of high polymers. If the degree of polymerisation (DP) is defined as the number ofsubunits in a molecule, the DP distribution is expressed by a single variable, b, the reciprocal of the number‐average DP. For a DP of i, the weight‐ and number‐fractions are, respectively, ib 2 (1−b) i−1 . and b(1−b) i−1 . The weight‐average DP is (2/b)−I. The distribution is identical with that produced by random degradation of an infinite molecule (b being the fraction of interchain disulphide bonds broken). The distribution predicts that there would be a significant amount of low mol. wt material: this is so in practice, such material being soluble in aqueous ethanol. The shape of a calculated curve corresponds, at least qualitatively, to those in the literature obtained by gel filtration when allowance is made for the mol. wt axis being on a logarithmic scale, for the longest molecules emerging together in the excluded peak and for diffusion. These experimental curves show that monomers are not the commonest species by weight (unless half gliadin consists of monomeric glutenin). This implies that glutenin has a linear, not a branched, molecule.