Study of wheat high molecular weight 1Dx5 subunit by ¹³C and ¹H solid‐state NMR. II. Roles of nonrepetitive terminal domains and length of repetitive domain

Abstract

This work follows a previous article that addressed the role of disulfide bonds in the behavior of the 1Dx5 subunit upon hydration. Here the roles of nonrepetitive terminal domains present and the length of the central repetitive domain in the hydration of 1Dx5 are investigated. This was achieved by comparing the hydration behavior of suitable model samples determined by (13)C- and (1)H-NMR: an alkylated 1Dx5 subunit (alk1Dx5), a recombinant 58-kDa peptide corresponding to the central repetitive domain of 1Dx5 (i.e., lacking the terminal domains), and two synthetic peptides (with 6 and 21 amino acid residues) based on the consensus repeat motifs of the central domain. The (13)C cross-polarization and magic angle spinning (MAS) experiments recorded as a function of hydration gave information about the protein or peptide fractions resisting plasticization. Conversely, (13)C single pulse excitation and (1)H-MAS gave information on the more plasticized segments. The results are consistent with the previous proposal of a hydrated network held by hydrogen-bonded glutamines and possibly hydrophobic interactions. The nonrepetitive terminal domains were found to induce water insolubility and a generally higher network hindrance. Shorter chain lengths were shown to increase plasticization and water solubility. However, at low water contents, the 21-mer peptide was characterized by higher hindrance in the megahertz and kilohertz frequency ranges compared to the longer peptide; and a tendency for a few hydrogen-bonded glutamines and hydrophobic residues to remain relatively hindered was still observed, as for the protein and large peptide. It is suggested that this ability is strongly dependent on the peptide primary structure.

The physics of baking: rheological and polymer molecular structure–function relationships in breadmaking

“…Gluten proteins comprise a highly polydisperse system of polymers, classically divided into two groups based on their extractability in alcohols: gliadins and glutenins. The gliadins are single-chain polypeptides with molecular weight (MW) ranging from 2 × 10 4 to 7 × 10 4 , whilst the glutenins are multiple-chain polymeric proteins in which individual polypeptides are thought to be linked into a network by intermolecular disulphide and hydrogen bonds to give a wide MWD [2] ranging between 10 5 to well beyond 10 8 . It is only recently that it has been possible to measure and quantify the high MW glutenin polymers known to responsible for variations in breadmaking quality using techniques such as dynamic light scattering [3][4][5][6], and their conformation and structure by techniques such as X-ray and electron scattering [7], NMR [8,9] and FTIR spectroscopy [10], hydrodynamic studies in solution [11] and AFM [12].…”

Applications of High-Resolution Solid-State NMR Spectroscopy in Food Science

“…Investigations on wheat glutenin subunits by CPMAS NMR revealed that the hydration induces plasticization depending on disulfide bonds. The study was carried out using dealkylated and alkylated forms of the protein.…”