Fragment Screening and Fast Micromolar Detection on a Benchtop NMR Spectrometer Boosted by Photoinduced Hyperpolarization

Rapid Protein-Ligand Affinity Determination by Photoinduced Hyperpolarized NMR

The binding affinity determination of protein-ligand complexes is a cornerstone of drug design. State-of-the-art techniques are limited by lengthy and expensive processes. Building upon our recently introduced novel screening method utilizing photochemically induced dynamic nuclear polarization (photo-CIDNP) NMR, we provide the methodological framework to determine binding affinities within 5-15 min using 0.1 mg of protein. The accuracy of our method is demonstrated for the affinity constants of peptides binding to a PDZ domain and fragment ligands binding to the protein PIN1. The method can also be extended to measure the affinity of nonphoto-CIDNP-polarizable ligands in competition binding experiments. Finally, we demonstrate a strong correlation between the ligand-reduced signals in photo-CIDNP-based NMR fragment screening and the well-established saturation transfer difference (STD) NMR. Thus, our methodology measures protein-ligand affinities in the micro- to millimolar range in only a few minutes and informs on the binding epitope in a single-scan experiment, opening new avenues for early stage drug discovery approaches.

LC-Photo-CIDNP hyperpolarization of biomolecules bearing a quasi-isolated spin pair: Magnetic-Field dependence via a rapid-shuttling device

Liquid-state low-concentration photochemically induced dynamic nuclear polarization (LC-photo-CIDNP) is an emerging technology tailored to enhance the sensitivity of NMR spectroscopy via LED- or laser-mediated optical irradiation. LC-photo-CIDNP is particularly useful to detect solvent-exposed aromatic residues (Trp, Tyr), either in isolation or within polypeptides and proteins. This study investigates the magnetic-field dependence of the LC-photo-CIDNP of Trp-α-13C-β,β,2,4,5,6,7-d7, a Trp isotopolog bearing a quasi-isolated 1Hα-13Cαspin pair (QISP). We employed a new rapid-shuttling side-illumination field-cycling device that enables ultra-fast (90-120 ms) vertical movements of NMR samples within the bore of a superconducting magnet. Thus, LC-photo-CIDNP hyperpolarization occurs at low field, while hyperpolarized signals are detected at high field (700 MHz). Resonance lineshapes were excellent, and the effect of several fields (1.18-7.08 T range) on hyperpolarization efficiency could be readily explored. Remarkably, unprecedented LC-photo-CIDNP enhancements ε ≅ 1,200 were obtained at 50 MHz (1.18 T), suggesting exciting avenues to hypersensitive LED-enhanced NMR in liquids at low field.