Quantification of Ligand-Membrane Interactions Using DNP-NMR Relaxometry.

Area of Science:

• Nuclear Magnetic Resonance (NMR) Spectroscopy
• Biophysical Chemistry
• Materials Science

Background:

• Understanding ligand-membrane interactions is crucial for drug discovery.
• Traditional NMR methods often lack the sensitivity to study weak binding events.
• Hyperpolarization techniques offer enhanced sensitivity for NMR measurements.

Purpose of the Study:

• To measure transverse relaxation rates (R2) of 19F spins from small molecule ligands interacting with phospholipid vesicles.
• To utilize dissolution dynamic nuclear polarization (D-DNP) for enhanced detection sensitivity.
• To characterize ligand-membrane binding equilibria and kinetics.

Main Methods:

• Measurement of R2 relaxation rates using DNP-enhanced 19F NMR.
• Modeling of bound ligand relaxation rates based on molecular dynamics.
• Quantification of binding parameters (f*R2,b)/KD and KD/f.
• Varied phospholipid vesicle compositions and concentrations.

Main Results:

• Calculated (f*R2,b)/KD parameter from R2 increase with lipid concentration.
• Estimated KD/f > 10 mM for ligand binding to 200 nm vesicles.
• Binding affinity was insensitive to cholesterol but reduced by vesicle aggregation.

Conclusions:

• DNP-enhanced R2 relaxation measurements effectively detect ligand-membrane binding and kinetics.
• The method is compatible with other NMR parameters (R1ρ, diffusion, Laplace NMR).
• This approach facilitates drug discovery and biomedical studies of membrane-ligand interactions.