EPR Characterization of Nitric Oxide Binding to Hemoglobin

摘要: Since the early work of Hermann (1865) followed by that Haurowitz (1924), Keilin and Hartree (1937) Gibson Roughton (1957)— to point out only a few landmarks—nitric oxide is like O2 CO, well-known ligand deoxygenated reduced hemoglobin.1,2 The complex was first characterized its red color with large absorbances b bands heme at 574.5 536 nm secondly magnetic susceptibility 3.07 Bohr magnetons,3–5 an electron paramagnetic resonance g-value close 2.0.6 property used reveal cooperative binding NO ferrous iron in analogous manner CO;2 second property, paramagnetism, made choice probe physiological site. This great importance period (late 60s-early 70s) when X-ray crystallographic data were still limited resolutions (2.8–3.5 A) referred quaternary structure methemo-globin—instead oxyhemoglobin due autoxidation under beams, as compared deoxyhemoglobin. Other spectroscopic methods such far-infrared or Raman then pioneer instruments hands very scientists, while EPR more readily accessible.