scholarly journals Electron Paramagnetic Resonance Investigation of Nitrite Binding in Myoglobin

2018 ◽  
Author(s):  
Matthew Bawn ◽  
Fraser MacMillan
Keyword(s):  
Electron Paramagnetic Resonance ◽  
High Spin ◽  
Nitrite Reductase ◽  
Binding Mode ◽  
Nitrite Reduction ◽  
Paramagnetic Resonance ◽  
High Ph ◽  
Hypoxic Conditions ◽  
Electron Paramagnetic ◽  
Iron Center

ABSTRACTIt has been proposed that myoglobin (Mb) may act as a nitrite reductase under hypoxic conditions. Any mechanism describing such activity should take into account the binding geometry of the ligand to the heme. Crystal structures of horse-heart Mb and human hemoglobin-nitrite complexes suggest that the anion adopts an uncommon O-nitrito binding mode. Electron Paramagnetic Resonance (EPR) spectroscopy was employed to investigate the nature of nitrite binding to Mb at pH values ranging from 6.5 to 10.8. Results suggest that for ferric Mb at low pH, nitrite binds in the O-bound nitrito mode resulting in a low-spin (LS) iron center. Further a high-spin (HS) iron center is observed at high pH in Mb-Nitrite with spectral values different to that of purely HS-Mb that is proposed to be due to an N-bound nitrite. The yields of these two species were found to be influenced by pH.BackgroundMyoglobin has been theorized to have a role as a nitrite reductase.ResultsO-bound nitrite produces a low-spin ferric heme complex, whilst at high pH a high-spin species is found proposed to be the N-bound form.ConclusionNitrite may bind to heme in myoglobin via N-nitro or O-nitrito mode.SignificanceThe mechanism of any nitrite reduction will depend on its binding to the heme cofactor.

Mössbauer, Electron Paramagnetic Resonance, and Theoretical Study of a High-Spin, Four-Coordinate Fe(II) Diketiminate Complex

2008 ◽  
Vol 47 (19) ◽  
pp. 8687-8695 ◽  
Author(s):  
Sebastian A. Stoian ◽  
Jeremy M. Smith ◽  
Patrick L. Holland ◽  
Eckard Münck ◽  
Emile L. Bominaar
Keyword(s):  
Electron Paramagnetic Resonance ◽  
High Spin ◽  
Theoretical Study ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic

scholarly journals Electron-paramagnetic-resonance studies of leghaemoglobins from soya-bean and cowpea root nodules. Identification of nitrosyl-leghaemoglobin in crude leghaemoglobin preparations

1977 ◽  
Vol 167 (2) ◽  
pp. 435-445 ◽  
Author(s):  
C. Sidney Maskall ◽  
John F. Gibson ◽  
Peter J. Dart
Keyword(s):  
Electron Paramagnetic Resonance ◽  
High Spin ◽  
Root Nodules ◽  
Deae Cellulose ◽  
Soya Bean ◽  
Paramagnetic Resonance ◽  
Imidazole Complexes ◽  
Electron Paramagnetic ◽  
Haem Iron ◽  
Nitrosyl Derivative

1. Leghaemoglobins from soya-bean (Glycine max) and cowpea (Vigna unguiculata) root nodules were purified by chromatography on DEAE-cellulose phosphate columns at pH8.0 and pH5.8, to avoid the relatively low pH (5.2) commonly used to purify these proteins. 2. E.p.r. (electron-paramagnetic-resonance) spectra of the fluoride, azide, hydroxide and cyanide complexes of these ferric leghaemoglobins were very similar to the spectra of the corresponding myoglobin derivatives, indicating that the immediate environment of the iron in leghaemoglobin and myoglobin is similar, an imidazole moiety of histidine being the proximal ligand to the haem iron [cf. Appleby, Blumberg, Peisach, Wittenberg & Wittenberg (1976) J. Biol. Chem.251, 6090–6096]. 3. E.p.r. spectra of the acid-metleghaemoglobins showed prominent high-spin features very near g=6 and g=2 and, unlike myoglobin, small low-spin absorptions near g=2.26, 2.72 and 3.14. The width of the g=6 absorption derivative at 10–20K was about 4–4.5mT, similar to the value for acid-methaemoglobin. In contrast, a recently published (Appleby et al., 1976) spectrum of acid-metleghaemoglobin a had less high-spin character and a much broader absorption derivative around g=6. 4. E.p.r. spectra of ferric leghaemoglobin nicotinate and imidazole complexes suggest that the low-spin absorption near g=3.14 can be attributed to a trace of ferric leghaemoglobin nicotinate, and those near g=2.26 and 2.72 are from an endogenous dihistidyl haemichrome. 5. A large e.p.r. signal at g=2 in all samples of crude leghaemoglobin was shown to be from nitrosyl-leghaemoglobin. A soya-bean sample contained 27±3% of the latter. A previously unidentified form of soya-bean ferrous leghaemoglobin a was shown to be its nitrosyl derivative. If this is not an artifact, and occurs in the root nodule, the nitrosyl radical may interfere with the function of leghaemoglobin.

Electron paramagnetic resonance studies of the high-spin molecule Cr10(OMe)20(O2CCMe3)10

2005 ◽  
Vol 86 (3) ◽  
pp. 032507 ◽  
Author(s):  
Sonia Sharmin ◽  
Arzhang Ardavan ◽  
Stephen J. Blundell ◽  
Amalia I. Coldea ◽  
Eric J. L. McInnes ◽  
...  
Keyword(s):  
Electron Paramagnetic Resonance ◽  
High Spin ◽  
Paramagnetic Resonance ◽  
Electron Paramagnetic
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