1H NMR Saturation Transfer Studies of Exogenous Ligands Binding to Metmyoglobin

Two-dimensional(2D) ¹H. nuclear magnetic resonance exchange spectroscopy, 1D saturation transfer have been utilized to study the binding of imidazole(lm), 1-Methylimidazole(Melm), 1-Ethylimidazole(Etlm) to the heme iron of metmyoglobin. Some heme peripheral proton resonance's of these complexes have been first time assigned. The rates and equilibrium constants for Im, Melrn, Etlm binding to metMb are calculated from the 2D peak amplitudes. Analysis of the heme methyl shifts indicates that the orientations of the binding Im, Melm, Etlm are very similar. The steric effects and hydrogen bonding between the distal histidine and bound ligand are important factors regulating affinity.