Conformational and Colloidal Stability of Macromolecules in Aqueous Salt Solutions
Open Access
- Author:
- Rogers, Bradley Allen
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- October 01, 2019
- Committee Members:
- Paul S Cremer, Dissertation Advisor/Co-Advisor
Paul S Cremer, Committee Chair/Co-Chair
Mark Maroncelli, Committee Member
Scott A Showalter, Committee Member
Michael Anthony Hickner, Outside Member
Philip C Bevilacqua, Program Head/Chair - Keywords:
- Ion-Specific Effects
Interfacial Water Structure
Protein-Protein Interactions
Liquid-Liquid Phase Separation
Hydrophobicity
Thermoresponsive Polymers
Temperature Gradient Microfluidics - Abstract:
- The conformational and colloidal stability of proteins in aqueous solutions are critical to the function of biological cells and the shelf-life of biopharmaceutical drug products. These properties of protein macromolecules are strongly influenced by cosolutes in the solution, including inorganic salt ions and non-ionic crowding agents. The intrinsic and cosolute-modulated properties of proteins are governed by specific interactions between proteins, water, and cosolutes. Herein, the non-covalent interactions that drive two phenomena are explored, including anion-induced denaturation of proteins and the liquid-liquid phase separation of therapeutic antibody solutions. In the first aim, protein folding is mimicked by thermoresponsive polymers model systems that undergo hydrophobic collapse upon heating. A combination of light scattering measurements as well as vibrational and nuclear magnetic resonance spectroscopies on these thermoresponsive polymers reveal that the structure of water-water hydrogen bonding at hydrophobic surfaces can modulate the binding affinity of weakly hydrated anions over several orders of magnitude. In the second aim, the colloidal phase separation of concentrated antibody formulations is imaged by dark-field microscopy on a temperature gradient microfluidics platform. This platform facilitates high-throughput measurements of phase separation across a range of temperatures and solution conditions, simultaneously. Analysis of the dark-field images over time reveals that the phase separation is a multistep reaction. Collectively, this work provides novel insights into the conformational and colloidal stability of proteins, which advance the current understanding of protein behavior in biological and biotechnological solutions.