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United States Department of Agriculture

Agricultural Research Service

Related Topics

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

Location: Plant Polymer Research

2012 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:

Progress:.
1)Dynamic light scattering was used to measure the size of small spheres made with starch or biodegradable polymers based on lactide and glycoside. These are currently being used to embed photosensitizers to be delivered to blood parasites that cause the disease leishmaniasis. Using nanoprecipitation fluidics, homogeneous particles with a size average of ~200 nm were produced..
2)Reverse microemulsion polymerization methodology is being developed to produce starch particles loaded with photosensitizers. Starch is crosslinked using phosphorous oxichloride. The size of the particles depends on the emulsification conditions, but we have been able to obtain particles with average size of about 200 nm, although the samples exhibit large polydispersion. Drawbacks have been mostly related to the solvent partitioning of the compound into the emulsion..
3)The instrument has been used successfully to assure the size reproducibility of the preparations as well as the size distribution of the particles..
4)Finally, the instrument provided by National Center for Agricultural Utilization Research (NCAUR), Plant Polymer Research (PPL) has been used to obtain the molecular weight of a dextrin sample using conventional light scattering techniques.


Last Modified: 9/10/2014
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