Date of Award

2017

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Chemistry

First Advisor

Feng Gai

Abstract

As ubiquitous and diverse biopolymers, proteins are dynamic molecules that are constantly engaging in inter- and intramolecular interactions responsible for their structure, fold, and function. Because of this, gaining a comprehensive understanding of the factors that control protein conformation and dynamics remains elusive as current experimental techniques often lack the ability to initiate and probe a specific interaction or conformational transition. For this reason, this thesis aims to develop methods to control and monitor protein conformations, conformational transitions, and dynamics in a site-specific manner, as well as to understand how specific and non-specific interactions affect the protein folding energy landscape. First, by using the co-solvent, trifluoroethanol (TFE), we show that the rate at which a peptide folds can be greatly impacted and thus controlled by the excluded volume effect. Secondly, we demonstrate the utility of several light-responsive molecules and reactions as methods to manipulate and investigate protein-folding processes. Using an azobenzene linker as a photo-initiator, we are able to increase the folding rate of a protein system by an order of magnitude by channeling a sub-population through a parallel, faster folding pathway. Additionally, we utilize a tryptophan-mediated electron transfer process to a nearby disulfide bond to strategically unfold a protein molecule with ultraviolet light. We also demonstrate the potential of two ruthenium polypyridyl complexes as ultrafast phototriggers of protein reactions. Finally, we develop several site-specific spectroscopic probes of protein structure and environment. Specifically, we demonstrate that a 13C-labeled aspartic acid residue constitutes a useful site-specific infrared probe for investigating salt-bridges and hydration dynamics of proteins, particularly in proteins containing several acidic amino acids. We also show that a proline-derivative, 4-oxoproline, possesses novel infrared properties that can be exploited to monitor the cis-trans isomerization process of individual proline residues in proteins.

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