45D-13 |
Protein-lipid interactions in zein films investigated by surface plasmon resonance |
Q. WANG and G. W. Padua. Dept. of Food Science & Human Nutrition, Univ. of Illinois, Urbana-Champaign, 382-D AESB, 1304 W. Pennsylvinia Ave., Urbana, IL 61801 In previous work, zein was plasticized with oleic acid and formed into sheets and films. Mechanical and barrier properties of films were believed to be controlled by the film structure and interactions between zein and plasticizer. Protein-lipid interactions in zein films are not well understood. Fundamental studies are needed to gain understanding on structure/function relations operating in zein films in order to enhance product quality and improve process design. The objective of this work was to explore the potential of surface plasmon resonance (SPR) and atomic forced microscopy (AFM) as analytical tools for studying zein adsorption to immobilized fatty acids in order to investigate protein-plasticizer interactions occurring in zein films. Experiments on the adsorption of a-zein (characterized by SDS-PAGE) from aqueous ethanol and 2-propanol solutions onto polar and nonpolar thiol-lipid surfaces are presented. Gold substrates were prepared by thermal evaporation on glass slides. Gold-coated surfaces were modified by depositing a self-assembled monolayer of either a long chain carboxylic acid terminated thiol (COOH(CH2)10SH) or methyl-terminated alkanethiol (CH3(CH2)7SH). Adsorption of zein from alcohol-water solutions onto the thiol-lipid monolayers was detected by surface plasmon resonance. Surface topography was characterized by AFM. Experimental measurements indicated that a-zein interacted with both polar and nonpolar surfaces. Zein concentration affected the thickness of the bound zein layer. Measured thickness of zein monolayer was 4.7 nm on polar surfaces and 4.6 nm on nonpolar ones. However, adsorption of zein onto the two thiol-lipids generated differences in surface topography. Surface coverage for polar surfaces was lower than for nonpolar ones, but average roughness was higher. The development of ring-shaped structures 45 nm in height was observed when zein accumulated on polar surfaces. SPR and AFM were effective experimental techniques to probe zein-oleic acid interactions and zein aggregation phenomena.
Session 45D, Food Packaging: General
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