Submitted to: Cereal Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/20/2007
Publication Date: 1/1/2007
Citation: Selling, G.W., Hamaker, S.A., Sessa, D.J. 2007. Effect of solvent and temperature on secondary and tertiary structure of zein by circular dichroism. Cereal Chemistry. 84:(3)265-270. Interpretive Summary: With the growing market for bio-ethanol, it is becoming important to develop high-value products using the co-products of this industry. One of the main underutilized co-product of this industry is zein. Zein is the principal corn protein. Historically zein has been used in the textile fibers and coatings industries. In order to be used in this market, zein was treated with reagents that improved the properties of zein after exposure to water. The technology used previously, if used today, would require significant investment to perform it safely. Alternative technologies being developed require that the zein be modified at certain sites on the protein. Some of these sites may be difficult to modify due to crowding. If the structure of the protein can be modified to become more open, subsequent modification with desired reagents may take place more readily. This basic study will enable us, and other researchers in the field, to develop techniques to define the structure of zein. By knowing the structure of zein, and understanding how to change its structure, we will be able to more readily modify zein in order to develop a technolgy that will be able to compete successfully with petroleum based products.
Technical Abstract: Circular dichroism studies were performed on various samples of commercial zein to determine how the secondary and tertiary structure changes with different solvents, temperatures or pH. It was found that alcoholic solvent type and common denaturants, such as SDS and low amounts of urea, had little effect on the secondary structure of zein. Utilization of dimethylformamide or acetic acid gave very small changes in tertiary structure. The dissolution of zein in 50 mM sodium hydroxide produces a zein with a random secondary structure and large changes in tertiary structure. Solutions of zein in 8M urea produced solutions with large changes in tertiary structure. Increasing the temperature of zein to 70 deg C in 80% ethanol-water reduced the amount of alpha-helix and had a negligible effect on the tertiary structure. Secondary structural changes that occurred with heating were reversible.