Development of Ligand-Observed Methods for Characterizing Protein-Ligand Binding with DNP-Enhanced NMR

Abstract

Ligand-observed NMR has evolved into a powerful high-throughput screening (HTS) tool for drug discovery through characterization of protein-ligand interactions. Hyperpolarization created by D-DNP can improve the sensitivity of NMR by >1000x, enabling binding characterization at micromolar or sub-micromolar protein concentrations near physiological conditions. Incorporating D-DNP, ligand-observed NMR methods for characterizing binding are developed. The first method enables 1H detection of strong binders through competitive binding. While direct observation of slowly exchanging ligands is challenging, we demonstrate that changes in R2 of a reporter ligand can indirectly probe the binding of a strong competing ligand. The second method features 19F-based detection of heteronuclear NOE created by polarization transfer from hyperpolarized water protons to ligand 19F spins. Hyperpolarization of water broadens the applicability, allowing the study of ligands with poor polarizability. Characterization of real-time water signal enhancement, required for accurate quantification of cross-relaxation rates (σ), is accomplished with a purpose-designed dual-channel spectrometer.