Mössbauer Spectroscopy of Iron Porphyrins

Sams, J. R.; Tsin, Tsang Bik

doi:10.1016/b978-0-12-220104-2.50016-8

Cited by 45 publications

(41 citation statements)

References 72 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The Mössbauer spectrum of the sample after reduction with sodium dithionite was recorded at 4.2 K in the presence of a 60-millitesla magnetic field oriented parallel to the ␥-beam (data not shown). The major species was a doublet with parameters ␦ ϭ 0.45 Ϯ 0.01 mm/s and ⌬E Q ϭ 1.12 Ϯ 0.02 mm/s, indicative of the low spin (S ϭ 0) bis(pyridine) heme adducts (39). This species represented 59 Ϯ 10% of the total spectral area, in agreement with the UV-visible pyridine hemochromogen determination.…”

Section: Resultssupporting

confidence: 63%

“…; Refs. [37][38][39], pyridine was added to the Mössbauer sample under alkaline conditions in order to form the well defined bis(pyridine) heme complex. The Mössbauer spectrum of the sample after reduction with sodium dithionite was recorded at 4.2 K in the presence of a 60-millitesla magnetic field oriented parallel to the ␥-beam (data not shown).…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

Characterization of the Iron-binding Site in Mammalian Ferrochelatase by Kinetic and Mössbauer Methods

Franco

Moura

et al. 1995

Journal of Biological Chemistry

View full text Add to dashboard Cite

All organisms utilize ferrochelatase (protoheme ferrolyase, EC 4.99.1.1) to catalyze the terminal step of the heme biosynthetic pathway, which involves the insertion of ferrous ion into protoporphyrin IX. Kinetic methods and Mö ssbauer spectroscopy have been used in an effort to characterize the ferrous ion-binding active site of recombinant murine ferrochelatase. The kinetic studies indicate that dithiothreitol, a reducing agent commonly used in ferrochelatase activity assays, interferes with the enzymatic production of heme. Ferrochelatase specific activity values determined under strictly anaerobic conditions are much greater than those obtained for the same enzyme under aerobic conditions and in the presence of dithiothreitol. Mö ssbauer spectroscopy conclusively demonstrates that, under the commonly used assay conditions, dithiothreitol chelates ferrous ion and hence competes with the enzyme for binding the ferrous substrate. Mö ssbauer spectroscopy of ferrous ion incubated with ferrochelatase in the absence of dithiothreitol shows a somewhat broad quadrupole doublet. Spectral analysis indicates that when 0.1 mM Fe(II) is added to 1.75 mM ferrochelatase, the overwhelming majority of the added ferrous ion is bound to the protein. The spectroscopic parameters for this bound species are ␦ ‫؍‬ 1.36 ؎ 0.03 mm/s and ⌬E Q ‫؍‬ 3.04 ؎ 0.06 mm/s, distinct from the larger ⌬E Q of a control sample of Fe(II) in buffer only. The parameters for the bound species are consistent with an active site composed of nitrogenous/ oxygenous ligands and inconsistent with the presence of sulfur ligands. This finding is in accord with the absence of conserved cysteines among the known ferrochelatase sequences. The implications these results have with regard to the mechanism of ferrochelatase activity are discussed.

show abstract

Section: Resultssupporting

confidence: 63%

Section: Resultsmentioning

confidence: 99%

Characterization of the Iron-binding Site in Mammalian Ferrochelatase by Kinetic and Mössbauer Methods

Franco

Moura

et al. 1995

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…This assignment is acceptable because of the equal areas under the components of the doublets. Such a kind of the asymmetry is characteristic for the temperature dependent relaxation processes [18][19][20] and positive sign of the V zz component of electric fi eld gradient (EFG) tensors. The positive sign of the V zz indicates that Fe ion has more negative charge in the porphyrin plane than the perpendicular direction to it [17].…”

Section: Resultsmentioning

confidence: 99%

Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex

2015

View full text Add to dashboard Cite

“…1, it may be concluded that the differences in the region R (0-2 Å) are meaningful and may point out some atomic rearrangements in the first coordination sphere of iron during aggregation. The Mössbauer isomer shift at 25 K of about 0.45 mm/s and 0.47 mm/s for iron porphyrin monomers and aggregates, respectively, as well as the weakly temperature dependent quadrupole splitting of 0.7 mm/s indicates the +3 high spin state of iron atoms located in the low symmetry sites [7,8].…”

Section: Coordination and Valence State Of Ironmentioning

confidence: 99%

Dynamics of iron in Fe-porphyrin aggregates studied by X-ray absorption and Mössbauer spectroscopy

2008

View full text Add to dashboard Cite

The iron-porphyrin aggregates were studied by optical absorption and fluorescence method, infrared spectroscopy, X-ray absorption and Mössbauer spectroscopy. The aggregation of porphyrin molecules strengthens the Fe-ligands bonds and accelerates the spin-spin relaxations. A significant speeding-up of relaxation was observed with lowering the temperature down to 25 K. The comparison of the EXAFS (Extended X-ray Absorption Fine Structure) and Mössbauer spectroscopy results enabled some separation of the individual Fe vibration from its collective movement with ligands.

show abstract

Mössbauer Spectroscopy of Iron Porphyrins

Cited by 45 publications

References 72 publications

Characterization of the Iron-binding Site in Mammalian Ferrochelatase by Kinetic and Mössbauer Methods

Characterization of the Iron-binding Site in Mammalian Ferrochelatase by Kinetic and Mössbauer Methods

Mössbauer spectroscopy of reduced forms of a Fe-tetraphenylporphyrine complex

Dynamics of iron in Fe-porphyrin aggregates studied by X-ray absorption and Mössbauer spectroscopy

Contact Info

Product

Resources

About