The dramatic effect of N-methylimidazole on trans axial ligand binding to ferric heme: experiment and theory
The binding energy of CO, O-2 and NO to isolated ferric heme, [(FeP)-P-III](+), was studied in the presence and absence of a sigma donor (N-methylimidazole and histidine) as the trans axial ligand. This study combines the experimental determination of binding enthalpies by equilibrium measurements in a low temperature ion trap using the van't Hoff equation and high level DFT calculations.