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On the viscoelastic mechanisms in cereal proteins: How can we use structural models on gluten viscoelasticity to functionalize non-gluten proteins?
M. Fevzioglu (1), O. H. Campanella (1), B. R. HAMAKER (1). (1) Purdue University, West Lafayette, IN, U.S.A.

Unlike numerous examples of elastic animal proteins, wheat gluten is the only plant protein to have elastic properties. Elasticity of gluten is attributed to a specific sub-group termed the high molecular weight glutenin subunits (HMW-GS). The elasticity of HMW-GS has been associated with its secondary structure. The repetitive central region of HMW-GS was found to play a key role in determining folding properties of gluten. They were shown to form beta-sheet and beta-turn structures and transitions between these structures were used to explain the stress/relaxation behavior of gluten. Corn protein, zein, can be made viscoelastic, but with inferior quality compared to gluten. Previous studies done in our lab indicated that the viscoelastic properties of zein can be improved in the presence of a co-protein, such as HMW-GS. Additionally, gluten and zein were shown to go through different structural transitions with co-protein addition. In gluten, the main transition was found to be between beta-sheet and beta-turn structures. On the other hand, zein was determined to go through alpha-helix to beta-sheet transition. Recent investigations done in our group on hydrated and solution state gluten indicated that there might be a link between specific types of beta-turns, such as type III beta-turns, and their folding to alpha-helix and beta-sheet structures. While two distinct peaks (1628 cm<sup>-1</sup> and 1639 cm<sup>-1</sup>) were determined in Amide I region for hydrated gluten, only one peak (1633 cm<sup>-1</sup>) was observed for gluten in solution state which might be due to formation of beta-sheet and beta-turn structures differing in hydrogen bonding strengths. The purpose of this presentation is to discuss the role of specific secondary structural motifs on gluten viscoelasticity and how this information can be used in manipulation of other cereal proteins to obtain viscoelastic structures.

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