Conformational studies of synthetic peptides corresponding to the repetitive regions of the high molecular weight (HMW) glutenin subunits of wheat

Circular dichroism and Fourier transform infrared spectra of three synthetic peptides based on the repeat motifs of the HMW subunits of glutenin showed that they formed β-turns when dissolved in trifluoroethanol, a solvent that favours ordered structures stabilized by hydrogen bonds. Peptide 1, based on the hexapeptide repeat motif, was predicted to form a type II β-turn, while peptides 2 and 3 (which span the functions between hexapeptide and nonapeptide motifs) were predicted to form overlapping turns of types II and I/III. These predictions are consistent with the structures determined in trifluoroethanol. In contrast all three peptides appeared to have unordered structures when dissolved in H₂O or D₂O. These results are discussed in relation to the conformations of the HMW subunits.