Measuring Biomolecular Structure and Interactions using Hyperpolarized Ligands
Christian Hilty
Professor, Chemistry Department, Texas A&M University
September 11, 2024
![Christian Hilty](https://bcbp.tamu.edu/wp-content/uploads/2024/07/hilty_full-1.jpg)
Seminar Details
Host: Dr. Jea-Hyun Cho
Time: 4:00-5:00pm
Location: BCBP Rm 108
Seminar Abstract
Nuclear spin hyperpolarization enables NMR measurements in the physiological concentration regime, at fast time scale and with enhanced selectivity. This presentation explores the use of hyperpolarized small molecules, ligands for proteins, for the determination of binding affinity and binding epitope structures for applications in drug discovery and the elucidation of basic biochemical processes. Hyperpolarization by dissolution dynamic nuclear polarization (D-DNP) followed by rapid injection and mixing provides signal enhancements of >103 for hydrogen, fluorine or carbon nuclei. Alternatively, hyperpolarization can be transferred from highly polarized water protons to spins of interest, whereby the water acts as a universal medium for boosting the NMR sensitivity. The spin polarization can be used for relaxation measurements to characterize the binding interaction. We show that the R2 relaxation dispersion correlates to the orientation of a ligand for the trypsin protein in the binding protein. An ultrafast NMR technique enables the measurement of the R2 relaxation from multiple 13C spins simultaneously. Rapid multi-dimensional NMR experiments incorporating intermolecular polarization transfer elucidate molecular contacts that can be used in structure calculations. Separate from the methods employing DNP hyperpolarization, we demonstrate the polarization of hydrogen or fluorine spins in biological ligands by parahydrogen induced polarization (PHIP) including through signal amplification by reversible exchange (SABRE). The polarization transfer complexes used by SABRE further allow to indirectly sense the ligand concentration through observation of their metal hydride signals in a medium containing reverse micelles, which solubilize the metal complexes and biological molecules at the same time. The generation of parahydrogen polarization does not require a high magnetic field, and the interaction of thus polarized molecules with proteins can be observed in conventional high-field NMR spectrometers, as well as at a low or ultra-low magnetic field.