Influence of porphyrin radical type on vanadium-oxygen double bond strength in vanadyl porphyrin cation radicals: implications for heme protein intermediates

Macor, Kathleen A.; Czernuszewicz, Roman S.; Spiro, Thomas G.

doi:10.1021/ic00335a044

Cited by 37 publications

(80 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…9. This shift to higher frequency upon cation radical formation is consistent with model compound studies wherein the (VϭO) of vanadyl porphyrin -cation radicals (which yield an 2 A 1u ground state) was shown to occur at a higher frequency than the corresponding (neutral) vanadyl porphyrin (43).…”

supporting

confidence: 87%

Resonance Raman Spectra of Native and Mesoheme-reconstituted Horseradish Peroxidase and Their Catalytic Intermediates

Kincaid

Zheng

Al-Mustafa

et al. 1996

Journal of Biological Chemistry

View full text Add to dashboard Cite

Resonance Raman studies of native and mesohemereconstituted horseradish peroxidase and their catalytic intermediates, known as Compounds I and II, have been conducted using both near UV (ϳ350 nm) and visible (406.7 nm) excitation. Careful power studies indicate that the authentic Compound I spectra are obtainable using near UV excitation, but that use of visible excitation results in contamination of the Compound I spectrum with the spectrum of a Compound II-like photoproduct. Using H 2 18 O 2 , the (Fe‫؍‬O) stretching modes for both systems are unambiguously identified, for the first time, at ϳ790 cm ؊1 . The authentic Compound I spectra are indicative of an 2 A 1u -like ground state for both the native and the mesoheme-reconstituted proteins. Finally, the possible biological implications of such information are briefly discussed.

show abstract

supporting

confidence: 87%

Resonance Raman Spectra of Native and Mesoheme-reconstituted Horseradish Peroxidase and Their Catalytic Intermediates

Kincaid

Zheng

Al-Mustafa

et al. 1996

Journal of Biological Chemistry

View full text Add to dashboard Cite

show abstract

“…Nonetheless, a 2 A 1u state for the compound I species of the native enzymes would indeed be consistent with the b-substituent pattern of the protoheme contained in horseradish and other peroxidases, in accord with the predictions of Spellane et al [97]. It has been remarked that the donor effect of the axial histidine might account for a 2 A 2u state for horseradish peroxidase compound I [115]. If the effective symmetry were to be lowered from D 4h to C 4v the metal d z 2 orbital would be able to interact with and destabilize the porphyrin a 2u orbital [115,120] since both transform as a 1 under C 4v .…”

supporting

confidence: 83%

“…In a much cited account, an upshift of 15 cm À1 was observed upon formation of the 2 A 1u p-cation radical from neutral oxovanadium(IV)OEP. A downshift of approximately the same amount was observed upon formation of the corresponding 2 A 2u TPP complex [115]. It had therefore been puzzling that these results did not coincide with data for iron porphyrin p-cation radicals.…”

mentioning

confidence: 81%

“…ClO [113]. These observations have been recently reconciled via reconsideration [117] of previous data [115] from the vanadyl porphyrin p-cation radicals. Oxovanadyl stretching frequencies now appear to be truly insensitive to the radical state.…”

mentioning

confidence: 85%

“…Oxovanadyl stretching frequencies now appear to be truly insensitive to the radical state. [117] It is felt that the previous conclusions [115] had been influenced by the presence of contaminating H 2 O or Cl À coordinating ligands. [117] Symmetry states of porphyrin p-cation radicals are now seen to have minimal influence on ferryl-oxo stretching frequencies.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Symmetry states of metalloporphyrin π-cation radicals, models for peroxidase compound I

Terner

Gold

Weiss

et al. 2001

J. Porphyrins Phthalocyanines

View full text Add to dashboard Cite

Oxoferryl porphyrin p-cation radical active sites of compound I intermediates which are found in enzymes such as peroxidases and catalases have been extensively modeled by oxidized synthetic metalloporphyrins. The electronic symmetry states of these compounds were initially assigned on the basis of electronic absorption data. In recent years new experimental and theoretical results have become available which have led to a re-evaluation and modification of the original assignments. A historical perspective of these developments is provided in the context of recent NMR, resonance Raman, and other spectroscopic data and theoretical calculations for the synthetic models and enzymatic systems.

show abstract

High-valent iron porphyrins

Gold

Weiss²

2000

J. Porphyrins Phthalocyanines

View full text Add to dashboard Cite

The term ‘high-valent’ refers to iron complexes of porphyrins and related macrocycles in which the oxidation state of the iron center exceeds III. High-valent iron porphyrins and chlorins are important biological transients whose intermediacy has been demonstrated in numerous peroxidase and catalase enzymes. Two species, compounds I and II, are spectroscopically detectable upon stoichiometric addition of monooxygen donors to resting ferric enzymes. Compounds I and II are formally two and one oxidizing equivalents respectively above the ferric state. In compound II the oxidizing equivalent has been shown by spectroscopic studies to be located on iron as an oxoiron(IV) unit. The spectroscopic and magnetic properties of compound I support the structural assignment of an S = 1 oxoiron(IV) unit magnetically coupled to a heme π-cation radical (S = 1/2). Studies on model hemes have contributed much to the understanding of protein chemistry. Much work has been accomplished with meso-tetaarylporphyrins and, more recently, with physiologically congruent meso-unsubstituted pyrrole β-substituted complexes. Compounds I of both proteins and synthetic models have been characterized by a wide array of spectroscopic methods, including UV-vis, NMR, resonance Raman, EPR, variable-temperature/variable-field magnetic Mössbauer, magnetic circular dichroism and extended X-ray absorption fine structure spectroscopy. Results of these studies are summarized. Recent developments, which promise to yield a detailed picture of electronic structure, are variable-temperature magnetic circular dichroism, studies in the pre-K-edge region and L-edge X-ray absorption spectroscopy. Time-resolved X-ray diffraction techniques have been applied to obtain the first structural data on the protein forms of compound I.

show abstract

Influence of porphyrin radical type on vanadium-oxygen double bond strength in vanadyl porphyrin cation radicals: implications for heme protein intermediates

Cited by 37 publications

References 1 publication

Resonance Raman Spectra of Native and Mesoheme-reconstituted Horseradish Peroxidase and Their Catalytic Intermediates

Resonance Raman Spectra of Native and Mesoheme-reconstituted Horseradish Peroxidase and Their Catalytic Intermediates

Symmetry states of metalloporphyrin π-cation radicals, models for peroxidase compound I

High-valent iron porphyrins

Contact Info

Product

Resources

About