Application of Relaxation Dispersion of Hyperpolarized 13C Spins to Protein-Ligand Binding

Nuclear spin relaxation dispersion parameters are proposed as indicators of the binding mode of a ligand to a protein. Hyperpolarization by dissolution dynamic nuclear polarization (D-DNP) provided a C-13 signal enhancement between 3000-6000 for the ligand 4-(trifluoromethyl) benzene-1-carboximidamide binding to trypsin. The measurement of C-13 R-2 relaxation dispersion was enabled without isotope enrichment, using a series of single-scan Carr-Purcell-Meiboom-Gill experiments with variable refocusing delays. The magnitude in dispersion for the spins of the ligand is correlated to the position with respect to the salt bridge between protein and the amidine group of the ligand, indicating the ligand binding orientation. Hyperpolarized relaxation dispersion is an alternative to chemical shift or NOE measurements for determining ligand binding modes.

Automated summary

Nuclear spin relaxation dispersion parameters can serve as indicators of the binding mode of a ligand to a protein. Hyperpolarization techniques, such as dissolution dynamic nuclear polarization, can provide signal enhancement without the need for isotope enrichment, offering an alternative method for determining ligand binding modes.