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Title:A Colloidal Science Approach to Characterize the Nanoscale Aggregation Behavior of Corn Protein Zein
Author(s):Haque, Munima
Doctoral Committee Chair(s):Bhalerao, K.D.,
Department / Program:Agricultural and Biological Engineering
Discipline:Agricultural and Biological Engineering
Degree Granting Institution:University of Illinois at Urbana-Champaign
Subject(s):Engineering, Biomedical
Biophysics, General
Abstract:The structure of zein, its hydropathic behavior, and its ability to form stable aggregates in colloidal solutions provides an excellent model to study hydrophobic proteins and aggregation processes. In this research the dissolution and aggregation behavior of zein in aqueous ethanol solutions was investigated. Its behavior was modeled as a micellar system, and its diffusion coefficients in varying ethanol-water combinations were measured.
A turbidity test was performed using 1-20 mg/ml zein concentrations over a range of 44-90% ethanol solutions to understand the overall zein behavior in different solvent conditions. Zein precipitated below 44% and above 90% ethanol concentrations. To increase experimental resolution, a dynamic light scattering experiment was performed for measuring the zein particle size and aggregation behavior. Results obtained from the dynamic light scattering reconfirmed that zein precipitates below ethanol concentration of 52% and above concentration of 90%. In between these two limits, zein forms a stable solution.
DLS was also used to investigate the diffusion coefficient variations of zein particles in aqueous ethanol solutions with varying temperatures. The temperature of the solutions was varied from 15-70°C, while the ethanol concentrations were varied from 44.1%-90.7%. In addition to confirming the fact that zein shows highest solubility at around 80% ethanol solution, this study also showed that the diffusion coefficient of zein can be modeled according to an Arrhenius-type relationship with respect to temperature.
Prior literature suggests that zein affects the viscosity of its solvent when in solution. Local variation in the microrheology of the zein solution was suspected to affect the diffusion coefficient of zein, and therefore the apparent particle size in DLS experiments. To test if zein causes rheological changes, 47 nm silica nanoparticles were introduced in dilute zein solutions to observe if they appeared to change their diffusion coefficient when in the vicinity of zein particles. The goal was to obtain a statistical estimate of the microrheological variation in solution due to the presence of zein aggregates. The variability is found to be significant in the cases for 100%, 87.6%, and 75.9% ethanol solutions. These experiments indicate that the presence of zein in solution could change the microrheology of the solution, although these experiments were not entirely conclusive, as it appeared that silica appeared to aggregate in pure silica-water-ethanol solutions in some cases.
Zein could well serve as an experimental object to learn much more about the nature of protein aggregation itself. There is promise for extension of this zein protein biophysics research and it can have potential importance for future applications in biomedical, bioprocessing, and biophysics arenas.
Issue Date:2009
Description:128 p.
Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.
Other Identifier(s):(UMI)AAI3362917
Date Available in IDEALS:2014-12-17
Date Deposited:2009

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