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978-3-8439-1561-8, Reihe Technische Chemie
Investigation of protein behavior at gas-liquid interfaces
137 Seiten, Dissertation Technische Universität Dortmund (2013), Softcover, A5
Most of the proteins act as surface active substances. They can adsorb to a gas-liquid interface creating gas-liquid dispersions like foams. This property is used in wastewater treatment or in food industry. Beside these application areas, the surface activity of proteins has been applied to separate proteins from each other. The technique that makes this possible is called foam fractionation. However, during foam fractionation it is possible that proteins change their structure upon adsorption to the interface. Therewith, the prediction of structural changes is important for the preservation of the protein functionality and the selection of proteins for special applications.
Till now it was not possible to predict the protein foamability and behavior at the gas-liquid interface. To increase the knowledge and identify protein properties necessary for successful adsorption to the gas-liquid interface, the molecular level of protein adsorption was examined. For the experimental investigation foam fractionation was applied. Model proteins BSA, lysozyme and β-casein were foamed and experimental conditions were varied using statistical design. Additionally model proteins were investigated before and after foam fractionation: Circular dichroism spectroscopy and Fourier transform infrared spectroscopy were used for the determination of the protein secondary structure in solution. Infrared reflection absorption spectroscopy was applied to provide information about protein structure at the gas-liquid interface.
The results derived from statistical approach and IR spectra showed that the protein properties namely, hydrophobicity, flexibility and secondary structure are of main importance to describe the protein adsorption process. Based on these findings, the protein adsorption and structural behavior at the interface of trypsin and horseradish peroxidase were predicted and experimentally validated following a guideline developed by Merz (2012). As predicted, trypsin showed better surface activity. Thus, by considering selected protein properties and the experimental conditions it was possible to predict the protein behavior at the gas-liquid interface.