LONG-RANGE EFFECTS IN LIGANDED HEMOGLOBIN INVESTIGATED BY NEUTRON ANDUV RAMAN-SCATTERING, FTIR, AND CD SPECTROSCOPIES

The numerous investigations that have focused on the iron binding site to explain the different affinity of hemoglobin for CO and O-2 are st ill without success. Thus, this work addresses the problem of nonlocal effects, which have been disregarded so far. We have investigated the protein behavior in relation to the iron-ligand nature. The present d ata Show that different parts of the protein, which are not in close c ontact with the heme pocket, are effectively influenced by the nature of the iron-ligand bond. Whereas oxyhemoglobin and carbonmonoxide hemo globin in solution exhibit the same molecular shapes and helical conte nts, different electrostatic interactions in association with a redist ribution of the strains occur in the protein matrix. Due to electric c ouplings of the heme to the protein, the whole molecule is sensitive t o the chemical nature of the iron-ligand bond. This suggests that long distance electrostatic interactions promote the energy transduction t hrough the protein molecule.