17G-12 |
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E. SHIMONI, Dept. of Food Engineering & Biotechnology, Technion-Israel Institute of Technology, Haifa, 32000, Israel, I. Zakharia, Technion, Haifa, 32000, Israel, and E. Kesselman, Tachnion, Haifa, 32000, Israel. (1) Justification The interactions between proteins and polysaccharides play key roles in determining the structure, texture and stability in various food systems. State of the art technologies such as Atomic force microscopy (AFM) and Near-field Scanning Optical Microscope (NSOM) has enabled the characterization of surfaces at the nano scale with sub-diffraction limit resolution. Combining AFM and NSOM allows the noninvasive, dynamic and in-situ optical and topographical imaging of molecular events on a spatial nanometer scale. To the best of our knowledge, no work is reported the literature studying the adsorption of proteins on polysaccharides by near-field optics. (2) Objectives The objective of this study was to establish the experimental procedures and methodologies for nano scale characterization of the adsorption of fluorescein-labelled bovine serum albumin (BSA-FITC) on grafted polygalacturonate surface. (3) Methods Surfaces were prepared by modifying silica surfaces with amino-propyltrimethoxysilane providing flat and homogeneous amino-terminated monolayer. Polygalacturonate was covalently attached to the aminosilane surface by carbodiimide reaction. Immersing polygalacturonate-coated silicon strip in BSA-FITC solution tested adsorption. Scans were performed at tapping mode in the Nanonics NSOM/AFM-100 system. The adsorption of protein on polygalacturonate was imaged with AFM/NSOM system (excitation at 488 nm). Laser light was delivered to the surface through cantilevered AFM-NSOM optical fiber probe, and the emitted fluorescence (515+/-10 nm) filtered and collected by an APD. (4) Results The results obtained in these experiments show uniform coating of the surfaces by polygalacturonate. We have obtained high-resolution images of BSA-FITC adsorbed onto the coated surfaces. The combination of NSOM technique with AFM allowed the detection of protein clusters on the carboxylated polygalacturonate surface. Preliminary in-situ nano scale surface charge measurements indicate that the protein adsorption may be correlated in the future with local surface charge. (5) Significance The present study demonstrates the direct nano-scale characterization of topographical features in combination with optical probing of BSA-FITC adsorption on the negatively charged polygalacturonate. The developed methodologies and techniques can be used for studies of food biopolymer interactions and functionality.
Session 17G, Food Engineering: Physical, chemical and electrical properties
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