CNRS RESEARCH DIRECTOR
CNRS RESEARCH ENGINEER
Ligand association to proteins constitutes a critical event in the activation or deactivation processes. Solution-state NMR can be amenable to high-resolution structure determination of various ligands in their protein-bound state by detecting dipolar interactions in a transferred mode. Based on observed dipolar interactions in NOESY spectra, it is possible to simultaneously determine, using a graphical approach, the auto (ρ) and cross (σ) relaxation rate constants in the bound state from 2D NOESY NMR experiments in the presence of chemical exchange .
Both ρ and σ can be graphically estimated simultaneously from the experimental ratio of cross to diagonal peak volumes from 2D NOESY NMR experiments, Πexp, knowing the koff, the relative population of ligand vs. receptor, and ρ in the free state (see pdf.file).
Fig. 1 illustrates two examples in the case of strong dipolar interactions, i.e. corresponding to short inter-proton distances in a rigid part of two unsaturated fatty acid compounds that are both agonists of the low affinity leukotriene G Protein-Coupled Receptor BLT2.
For further information, see ref 3.