Date of Award
Doctor of Philosophy (PhD)
Biochemistry & Molecular Biophysics
A. J. Wand
Water is fundamental to all aspects of protein function including folding, stability, catalysis, and dynamics. The unique characteristics of water make it the ideal solvent for supporting life but also make it incredibly difficult to study. While much has been learned about the role of water in protein function, a site resolved understanding of these interactions has remained elusive thereby leaving a large hole in the biophysical puzzle. Experimental techniques that provide a site-resolved view of protein hydration without mutation of the protein are necessary to understand the thermodynamic role of water on protein function. It has been shown that the combination of Nuclear Magnetic Resonance (NMR) spectroscopy and encapsulation of proteins within the core of reverse micelles can satisfy these requirements. The goal of this thesis is to apply and expand upon currently established techniques to make it generally applicable to all protein systems. First, previously established methods were used to examine the internal hydration patterns of staphylococcal nuclease variants with internal ionizable groups. The results demonstrate that water penetrates the hydrophobic core to stabilize buried ionizable groups. This study illustrates the utility of NMR detected hydration measurements for longstanding biophysical questions. Next, two methods to reduce data collection times were implemented for hydration dynamics measurements. This necessary time savings provides a platform for assessing the reproducibility and precision of NMR derived hydration measurements. A new data fitting method that allows for quantitative hydration dynamics measurements of protein regions generally contaminated by hydrogen exchange is introduced. Finally, one of the remaining artifacts associated with hydration dynamics measurements detected by NMR is addressed: hydrogen exchange relayed artifacts. This was accomplished by developing experiments to decouple the relaying spin and applying a new data fitting method. These methods allow for the first site and time resolved study of protein hydration in the absence of artifact is presented. These techniques introduced were applied to Ubiquitin encapsulated in AOT reverse micelles. The majority of slowed waters reside in concave regions of the protein surface. This suggests surface curvature is one of the contributing factors for the slowing of hydration waters. The experiments presented demonstrate the utility of using NMR for measuring protein-water interactions. The work presented expands and improves upon existing methodologies and provides a framework for artifact free site resolved measurement of protein water-interactions in all protein systems.
Jorge, Christine, "Optimization Of Nuclear Magnetic Resonance Spectroscopy Methods For Measuring Protein Hydration In Reverse Micelles" (2018). Publicly Accessible Penn Dissertations. 3133.