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United States Department of Agriculture

Agricultural Research Service

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Research Project: Determination of Structure-Property Relationships in Biological Macromolecules Using Biophysical Approaches

Location: Plant Polymer Research

2011 Annual Report


1a.Objectives (from AD-416)
The objective of this cooperative research project is to study the properties of biological macromolecules (starches, proteins, etc.) as a function of different experimental variables (temperature, solvent composition, concentration of additives, etc.) using laser based scattering techniques.


1b.Approach (from AD-416)
The collaboration is centered on characterizing the behavior of corn products and their derivatives in solution or suspension via light scattering experiments. Both static and dynamic light scattering experiments are going to be carried out. The Agricultural Research Service (ARS) will provide samples of the materials to be studied and Illinois State University (ISU) will perform the experiments on an instrument provided (on loan) by the ARS. Both static and dynamic light scattering measurements provide physical information about a molecular system as it dynamically stands in solution. Physical parameters to be measured are the weight-average molecular weight, the radius of gyration, the second virial coefficient, the translational diffusion coefficient, and the hydrodynamic radius. The dependence of these values on different experimental variables such as temperature, solvent composition, presence of additives (ions, cross-linking agents, etc.), and solution settling time will be measured. The effect of these variables in the physical properties above will provide insight in the process of molecular aggregation, and how chemical interactions play a role on it.

Regular meetings between the staff at ARS and ISU will be held to discuss experiments and results. After both parties design an experiment, ISU scientists will perform the experiments and report the results to the ARS staff. Analysis of the results and their implications to the system under study will be discussed. Results and analysis will be presented at meetings, and/or published in peer-reviewed journals.


3.Progress Report

The methodology to produce starch particles loaded with photosensitizers via a reverse microemulsion polymerization was improved. Starch is crosslinked using phosphorous oxichloride. The size of the particles depends on the emulsification conditions and particles with average size of 200 nm were formed, although the samples exhibit large polydispersion. As expected, this methodology has worked better at encapsulating water-soluble photosensitizers. Dynamic light scattering was used to measure the particle size of small spheres made with starch or biodegradable polymers based on lactide and glycoside via nanoprecipitation. The embedded photosensitizers are used to control blood-born parasitic diseases such as leishmaniasis. This project was monitored by e-mails and phone conversations between the cooperator and the Authorized Departmental Officer's Designated Representative (ADODR).


Last Modified: 8/19/2014
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