Date of Award

2013

Degree Type

Thesis

Department

Chemical and Biomedical Engineering

First Advisor

Holland, Nolan

Subject Headings

Polypeptides, Elastin, Polymers, pH-responsive, ELPs

Abstract

Elastin-like polypeptides (ELP) are environmentally responsive polymers that exhibit phase transition behavior in response to various stimuli such as temperature, pH and irradiation. In this work, we focused on pH-responsive ELPs. It has been shown that pH value, configurations of ELPs, ELP concentration, and salt concentration can impact the phase transition behavior of pH-responsive ELPs. Quantitative models have been developed to engineer various linear ELPs, but there has not been any detailed study for engineering ionizable ELP with non-linear configurations. In this study, we designed, synthesized, and characterized pH-responsive ELPs with two different configurations. One is linear ELP, (GVGVPGEGVPGVGVP)12, and the other one is a three-armed star ELP, (GVGVPGEGVPGVGVP)12-foldon. Three ELP-foldon chains fold as a trimer in solutions. These constructs were synthesized by molecular biology techniques and characterized by different methods. A modified model based on previous studies was used to describe the pH-dependent reversible phase transition in response to their solution environment. The model was validated with pH-responsive ELPs with different configurations, i.e., linear and trimer. The phase transition of both ELPs fit this model across a range of pH. These results demonstrate that we are able to rationally design responsive polypeptides with different configurations whose transition can be triggered at a specified pH

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