Abstract
In drug discovery, ligands are sought that modulate the (mal-)function of medicinally relevant target proteins. In order to develop new drugs, typically a multitude of potential ligands are initially screened for binding and subsequently characterized for their affinity. Nuclear magnetic resonance (NMR) is a well-established and highly sensitive technology for characterizing such interactions. However, it has limited throughput, because only one sample can be measured at a time. In contrast, magnetic resonance imaging (MRI) is inherently parallel and MR parameters can conveniently be encoded in its images, potentially offering increased sample throughput. We explore this application using a custom-built 9-fold sample holder and a 19F-MRI coil. With this setup, we show that ligand binding can be detected by T2-weighted 19F-MRI using 4-(trifluoromethyl)benzamidine (TFBA) and trypsin as the reporter ligand and target protein, respectively. Furthermore, we demonstrate that the affinity of nonfluorinated ligands can be determined in a competition format by monitoring the dose-dependent displacement of TFBA. By comparing 19F-T2-weighted MR images of TFBA in the presence of different benzamidine (BA) concentrations-all recorded in parallel-the affinity of BA could be derived. Therefore, this approach promises parallel characterization of protein-ligand interactions and increased throughput of biochemical assays, with potential for increased sensitivity when combined with hyperpolarization techniques.