Date of Award

2011

Degree Type

Thesis

Department

Chemical and Biomedical Engineering

First Advisor

Holland, Nolan

Subject Headings

Polypeptides, Elastin, Viscosity, Polymers

Abstract

Elastin-like polypeptides (ELPs) are a class of polypeptide polymers that are gaining interest in various potential applications. These polymers are responsive to the changes in their environment by exhibiting conformational changes and aggregation. Monodisperse elastin-like polypeptides, (GVGVP)40, (GVGVP)40-foldon, and (GVGVP)60-foldon are made in bacterial expression system. An Ubbelohde capillary viscometer was set up to characterize the structural changes of these ELPs in phosphate buffered saline (PBS) solution. For the ELP-foldon, the relative viscosity measurements were utilized to calculate the intrinsic viscosities using Kraemer and Huggins equations. The known molecular weights of the ELPs and the experimentally determined intrinsic viscosities facilitated the calculation of the Mark-Houwink-Sakurada constants. The value of the exponential a in the Mark-Houwink-Sakurada equation was 0.69 at 20°C and it decreased as the temperature increased until it reached 0.51 at 26°C. The observed changes in a indicate that the conformation of the polymer coils changes from expanded and hydrated coils to theta coils. Viscosity measurements were limited in this project by concentration, since low concentrations produced small specific viscosities with large errors. A second limitation on the viscosity measurements was the aggregation of the polymers. The polymers aggregated at their phase transition temperature, Tt, and they phase separated

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