Xe Sensing via Insights from Noble-Gas Protein Interactions
Abstract
Noble gases such as Xe bind to proteins, and impact their structure, dynamics and activities. We will elucidate the molecular interactions between Xe and proteins by examining the dependence of protein structure and function on Xe binding. We will utilize UV resonance Raman spectroscopy (UVRR) to determine the factors leading to large Xe association constants because UVRR uniquely probes residues lining the Xe binding cavity. UVRR excitation within the 200 nm ???* transitions of the protein backbone enables protein secondary structure determinations. We will monitor interactions between noble gases such as Xe and protein sidechains and backbone peptide bonds. In addition, excitation within sidechain absorptions enhance their vibrational modes, which enables determination of their conformations, solvent exposures and hydrogen bonding. Protein side chains may modulate the Xe electron cloud to generate charge transfer electronic transitions to produce resonance Raman enhancements that highlight Xe-protein interactions at the Xe protein cavity interface. We will also utilize circular dichroism, electronic absorption and fluorescence to further probe interactions of Xe with the protein sidechains and the protein backbone peptide bonds. In addition, we will employ molecular modeling to gain insight into Xe-protein interactions. For example, there are over 120 high resolution Xe bound protein X-ray crystal structures in the Protein Data Bank from which we can derive Xe-protein interaction information and incorporate such information into the Rosetta molecular modeling suite for protein structure prediction and design. We will also examine the absorption spectra of these proteins to search for charge transfer absorption bands that could be used as highly sensitive monitors of Xe-protein binding. Further, we will utilize glucose oxidase (GOx) as a model enzyme to study the functional impact of Xe binding. Xe reduces the catalytic output of GOx by ~ 91%. FLIR Detection will develop an electrochemical assay to monitor GOx activity to measure the effects of Xe binding on enzyme rates. This information will then be used to inform our molecular de novo protein design efforts that will develop a biological reporter of Xe with superior sensitivity and selectivity over methods currently available. We will optimize these de novo proteins to increase their Xe affinities, in order to enable the fabrication of superior Xe binding materials.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jul 16, 2019
- Source ID
- HDTRA11810017
Entities
People
- Sanford A Asher
Organizations
- Defense Threat Reduction Agency
- University of Pittsburgh