Biomaterial Database

Single-crystal electron paramagnetic resonance studies of photolyzed oxy- and nitric oxide-cobalt myoglobins. 1982

H Hori, and M Ikeda-Saito, and J S Leigh, and T Yonetani

Low-temperature photodissociation of oxygen from oxy-cobalt myoglobin was studied by single-crystal electron paramagnetic resonance (EPR) spectroscopy at 5 K. The photolyzed oxy-cobalt myoglobin exhibited an EPR spectrum consisting of two nonequivalent sets (species I and II) of the principal values and eigenvectors of the g tensors: g1I = 3.55, g2I = 3.47, and g3I = 2.26 for species I, and g1II = 2.04, g2II = 1.93, and g3II = 1.86 for species II, which resembled neither the deoxy nor the oxy form. Possible models of the photodissociated state of oxy-cobalt myoglobin are proposed by comparison with cobalt porphyrin complexes. The photolyzed product of nitric oxide-cobalt myoglobin exhibited new EPR signals at g = 4.3 and a very broad signal at around g = 2. The principal g values have been determined from the single-crystal EPR measurements: g1 = 4.39, g2 = 4.27, and g3 = 4.00. Analysis of another EPR signal around g = 2 was difficult due to its broadness. Magnetic interactions were observed. An isotropic EPR signal at g = 4.3 suggested a weakly spin-coupled system between cobaltous spin (S = 1/2 or 3/2) and nitric oxide spin (S = 1/2).

UI	MeSH Term	Description	Entries
D008027	Light	That portion of the electromagnetic spectrum in the visible, ultraviolet, and infrared range.	Light, Visible,Photoradiation,Radiation, Visible,Visible Radiation,Photoradiations,Radiations, Visible,Visible Light,Visible Radiations
D009211	Myoglobin	A conjugated protein which is the oxygen-transporting pigment of muscle. It is made up of one globin polypeptide chain and one heme group.
D009569	Nitric Oxide	A free radical gas produced endogenously by a variety of mammalian cells, synthesized from ARGININE by NITRIC OXIDE SYNTHASE. Nitric oxide is one of the ENDOTHELIUM-DEPENDENT RELAXING FACTORS released by the vascular endothelium and mediates VASODILATION. It also inhibits platelet aggregation, induces disaggregation of aggregated platelets, and inhibits platelet adhesion to the vascular endothelium. Nitric oxide activates cytosolic GUANYLATE CYCLASE and thus elevates intracellular levels of CYCLIC GMP.	Endogenous Nitrate Vasodilator,Mononitrogen Monoxide,Nitric Oxide, Endothelium-Derived,Nitrogen Monoxide,Endothelium-Derived Nitric Oxide,Monoxide, Mononitrogen,Monoxide, Nitrogen,Nitrate Vasodilator, Endogenous,Nitric Oxide, Endothelium Derived,Oxide, Nitric,Vasodilator, Endogenous Nitrate
D010782	Photolysis	Chemical bond cleavage reactions resulting from absorption of radiant energy.	Photodegradation
D004578	Electron Spin Resonance Spectroscopy	A technique applicable to the wide variety of substances which exhibit paramagnetism because of the magnetic moments of unpaired electrons. The spectra are useful for detection and identification, for determination of electron structure, for study of interactions between molecules, and for measurement of nuclear spins and moments. (From McGraw-Hill Encyclopedia of Science and Technology, 7th edition) Electron nuclear double resonance (ENDOR) spectroscopy is a variant of the technique which can give enhanced resolution. Electron spin resonance analysis can now be used in vivo, including imaging applications such as MAGNETIC RESONANCE IMAGING.	ENDOR,Electron Nuclear Double Resonance,Electron Paramagnetic Resonance,Paramagnetic Resonance,Electron Spin Resonance,Paramagnetic Resonance, Electron,Resonance, Electron Paramagnetic,Resonance, Electron Spin,Resonance, Paramagnetic
D013696	Temperature	The property of objects that determines the direction of heat flow when they are placed in direct thermal contact. The temperature is the energy of microscopic motions (vibrational and translational) of the particles of atoms.	Temperatures