An infrared study of NO bonding to heme B and hemoglobin A. Evidence for inositol hexaphosphate induced cleavage of proximal histidine to iron bonds.
Five- and six-coordinate nitrosyl hemes have been prepared and their infrared, electron paramagnetic resonance (EPR), and visible-Soret spectra compared with the corresponding spectra for nitrosyl hemoglobin A (Hba-NO) determined both in the presence and the absence of inositol hexaphosphate (IHP).  The five- and six-coordinate NO complexes prepared from either dipyridine or pyridine carbonyl protoheme dimethyl ester had N-O stretch bands (nuno) near 1675 and 1625 cm-1, respectively.  These frequencies are sensitive to change in solvent (nuno decreased as the dipole moment of the solvent increased) and, with six-coordinate species, to changes in trans ligand.  However, these solvent and trans ligand effects were small compared with the difference (ca. 50 cm-11) between five- and six -coordinate species.  The nature of the trans ligand affected the relative proportions of the two...
D001665:Binding Sites; D006418:Heme; D006454:Hemoglobins / Q000032:analysis; D006639:Histidine / Q000032:analysis; D006801:Humans; D007294:Inositol / Q000031:analogs & derivatives*; D007501:Iron / Q000097:blood; D008958:Models, Molecular; D008968:Molecular Conformation; D009569:Nitric Oxide; D010833:Phytic Acid / Q000097:blood*; D011485:Protein Binding; D011487:Protein Conformation; D013055:Spectrophotometry, Infrared
D006454:Hemoglobins; D009569:Nitric Oxide; D006418:Heme; D007294:Inositol; D006639:Histidine; D010833:Phytic Acid; D007501:Iron