Parallelized Ligand Screening Using Dissolution Dynamic Nuclear Polarization

Protein ligand interactions are frequently screened using nuclear magnetic resonance (NMR) spectroscopy. The dissociation constant (K-D) of a ligand of interest can be determined, via a spin spin relaxation measurement of a reporter ligand in a single scan when using hyperpolarization by means of dissolution dynamic nuclear polarization (D-DNP). Despite nearly instantaneous signal acquisition, a limitation of D-DNP for the screening of protein ligand interactions is the required polarization time on the order of tens of minutes. Here, we introduce a multiplexed NMR experiment, where a single hyperpolarized ligand sample is rapidly mixed with protein injected into two flow cells. NMR detection is achieved simultaneously on both channels, resulting in a chemical shift resolved spin relaxation measurement. Spectral resolution allows the use of reference compounds for accurate quantification of concentrations. Simultaneous use of two concentration ratios between protein and ligand broadens the range of K-D that is accurately measurable in a single experiment to at least an order of magnitude. In a comparison of inhibitors for the protein trypsin, the average K-D values of benzamidine and benzylamine were found to be 12.6 +/- 1.4 mu M and 207 +/- 22 mu M from three measurements, based on K-D = 142 mu M assumed known for the reporter ligand 4-(trifluoromethyl)benzene-l-carboximidamide. Typical confidence ranges at 95% evaluated for single experiments were (8.3 mu M, 20 mu M) and (151 mu M, 328 mu M). The multiplexed detection of two or more hyperpolarized samples increases throughput of D-DNP by the same factor, improving the applicability to most multipoint measurements that would traditionally be achieved using titrations.