TY - JOUR
T1 - Electronic and stereochemical characterizations of the photoinduced intermediates of nitrosyl complexes of metal (S = 5/2)-substituted hemoproteins trapped at low temperature
AU - Hori, H.
AU - Ikeda-Saito, M.
AU - Lang, G.
AU - Yonetani, T.
N1 - Copyright:
Copyright 2007 Elsevier B.V., All rights reserved.
PY - 1990
Y1 - 1990
N2 - Low temperature photolysis of nitric oxide from the nitrosyl complexes of ferric myoglobin (NO-Fe(III)Mb) and manganese(II)-prophyrin-substituted myoglobin (NO-Mn(II)Mb) was examined by electron paramagnetic resonance (EPR) spectroscopy in order to elucidate the electronic and structural natures of the photoinduced intermediates of these hemoprotein-ligand complexes trapped at low temperature. The photoproduct of NO-Fe(III)Mb at 5 K exhibited entirely new X-band EPR absorptions in the magnetic field strength from 0 to 0.4 tesla. The widespread absorption together with distinct, sharp zero-field absorption was consistently observed in the photoproduct of the isoelectronic NO-Mn(II)Mb. These novel ERP signals indicate a spin-coupled pair with an effective spin of S = 2 between the high spin metal center (S = 5/2) and the photodissociated NO (S = 1/2) trapped adjacent to the metal center. On the other hand, the photolyzed form of nitrosyl complexes of Fe(III)- and Mn(II)-Glycera hemoglobins, in which the distal histidine of Mb is replaced by a leucyl residue, exhibited somewhat broader EPR absorptions similar to those of the corresponding native Fe(III)- or unliganded Mn(II)-Glycera hemoglobins, respectively, indicating that the photodissociated NO molecule moved farther away from the metal center in the heme pocket. These observations show the importance of the interaction of the distal residue with the ligand in determining the nature of the photolyzed states.
AB - Low temperature photolysis of nitric oxide from the nitrosyl complexes of ferric myoglobin (NO-Fe(III)Mb) and manganese(II)-prophyrin-substituted myoglobin (NO-Mn(II)Mb) was examined by electron paramagnetic resonance (EPR) spectroscopy in order to elucidate the electronic and structural natures of the photoinduced intermediates of these hemoprotein-ligand complexes trapped at low temperature. The photoproduct of NO-Fe(III)Mb at 5 K exhibited entirely new X-band EPR absorptions in the magnetic field strength from 0 to 0.4 tesla. The widespread absorption together with distinct, sharp zero-field absorption was consistently observed in the photoproduct of the isoelectronic NO-Mn(II)Mb. These novel ERP signals indicate a spin-coupled pair with an effective spin of S = 2 between the high spin metal center (S = 5/2) and the photodissociated NO (S = 1/2) trapped adjacent to the metal center. On the other hand, the photolyzed form of nitrosyl complexes of Fe(III)- and Mn(II)-Glycera hemoglobins, in which the distal histidine of Mb is replaced by a leucyl residue, exhibited somewhat broader EPR absorptions similar to those of the corresponding native Fe(III)- or unliganded Mn(II)-Glycera hemoglobins, respectively, indicating that the photodissociated NO molecule moved farther away from the metal center in the heme pocket. These observations show the importance of the interaction of the distal residue with the ligand in determining the nature of the photolyzed states.
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M3 - Article
C2 - 2168399
AN - SCOPUS:0025140905
VL - 265
SP - 15028
EP - 15033
JO - Journal of Biological Chemistry
JF - Journal of Biological Chemistry
SN - 0021-9258
IS - 25
ER -