Abstract
Catalysts which functionally mimic the bacterial dimanganese catalase enzymes have been synthesized and their structure, electrochemical, redox, and EPR spectra have been compared to the enzyme. These compounds are formulated as [LMn2 II,IIX]Y2, μ-X = CH3CO2, ClCH2CO2; Y = ClO4, BPh4, CH3CO2, possessing a bridging μ-alkoxide from the ligand, HL = N,N,N',N'-tetrakis(2-methylenebenzimidazole)-1,3-diaminopropan-2-ol. An X-ray diffraction structure of [LMn2(CH3CO2)(butanol)] (C1O4)2·H2O, in the monoclinic space group P2(1)/c, confirmed the anticipated N6O septadentate coordination of the HL ligand, the bridging μ-acetate, and revealed both five- and six-coordinate Mn ions; the latter arising from a butanol solvent molecule. This contrasts with the six-coordinate Mn ions observed for the μ-Cl and μ-OH derivatives, LMn2Cl3 and LMn2(OH)Br2 (Mathur et al. J. Am. Chem. Soc. 1987, 109, 5227-5232). Like the enzyme, three electrons can be removed from these complexes to form four oxidation states ranging from Mn2 II,II to Mn2 III,IV. Three of these have been characterized by EPR and found to possess electronic ground states, MnIII electron orbital configurations, 55Mn hyperfine parameters, and Heisenberg exchange interactions analogous to those observed in the enzyme. For the μ-carboxylate derivatives electrochemistry reveals the initial oxidation process involves loss of two electrons at 0.81-0.86 V, forming Mn2 III,III, followed by dismutation to yield a Mn2 II,III and Mn2 III,IV species. By contrast, the μ-Cl and μ-OH derivatives oxidize by an initial one-electron process (0.49-0.54 V). For the μ-carboxylate derivatives chemical oxidation with Pb(OAc)4 also reveals an initial two-electron oxidation to a Mn2 III,III species, which dismutates to form both Mn2 II,III and Mn2 III,IV species. The two Mn2 II,III species formed by these methods exhibit 55Mn hyperfine fields differing in magnitude by 9% (150 G), implying different Mn coordination environments induced by the electrolyte. The different ligand coordination observed in the enzyme (predominantly oxo and carboxylato) appears to be responsible for stabilization of the MnCatIII,III oxidation state as the resting state.
| Original language | English |
|---|---|
| Pages (from-to) | 891-897 |
| Number of pages | 7 |
| Journal | Journal of the American Chemical Society |
| Volume | 116 |
| Issue number | 3 |
| Publication status | Published - Feb 9 1994 |
Fingerprint
Keywords
- Catalase
- Electrochemical
- Enzyme
- EPR
- Hydrogen peroxide
- Manganese
- X-ray synthesis
ASJC Scopus subject areas
- Chemistry(all)
Cite this
Structural and functional models of the dimanganese catalase enzymes. 2. Structure, electrochemical, redox, and EPR properties. / Pessiki, P. J.; Khangulov, S. V.; Ho, D. M.; Dismukes, G Charles.
In: Journal of the American Chemical Society, Vol. 116, No. 3, 09.02.1994, p. 891-897.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Structural and functional models of the dimanganese catalase enzymes. 2. Structure, electrochemical, redox, and EPR properties
AU - Pessiki, P. J.
AU - Khangulov, S. V.
AU - Ho, D. M.
AU - Dismukes, G Charles
PY - 1994/2/9
Y1 - 1994/2/9
N2 - Catalysts which functionally mimic the bacterial dimanganese catalase enzymes have been synthesized and their structure, electrochemical, redox, and EPR spectra have been compared to the enzyme. These compounds are formulated as [LMn2 II,IIX]Y2, μ-X = CH3CO2, ClCH2CO2; Y = ClO4, BPh4, CH3CO2, possessing a bridging μ-alkoxide from the ligand, HL = N,N,N',N'-tetrakis(2-methylenebenzimidazole)-1,3-diaminopropan-2-ol. An X-ray diffraction structure of [LMn2(CH3CO2)(butanol)] (C1O4)2·H2O, in the monoclinic space group P2(1)/c, confirmed the anticipated N6O septadentate coordination of the HL ligand, the bridging μ-acetate, and revealed both five- and six-coordinate Mn ions; the latter arising from a butanol solvent molecule. This contrasts with the six-coordinate Mn ions observed for the μ-Cl and μ-OH derivatives, LMn2Cl3 and LMn2(OH)Br2 (Mathur et al. J. Am. Chem. Soc. 1987, 109, 5227-5232). Like the enzyme, three electrons can be removed from these complexes to form four oxidation states ranging from Mn2 II,II to Mn2 III,IV. Three of these have been characterized by EPR and found to possess electronic ground states, MnIII electron orbital configurations, 55Mn hyperfine parameters, and Heisenberg exchange interactions analogous to those observed in the enzyme. For the μ-carboxylate derivatives electrochemistry reveals the initial oxidation process involves loss of two electrons at 0.81-0.86 V, forming Mn2 III,III, followed by dismutation to yield a Mn2 II,III and Mn2 III,IV species. By contrast, the μ-Cl and μ-OH derivatives oxidize by an initial one-electron process (0.49-0.54 V). For the μ-carboxylate derivatives chemical oxidation with Pb(OAc)4 also reveals an initial two-electron oxidation to a Mn2 III,III species, which dismutates to form both Mn2 II,III and Mn2 III,IV species. The two Mn2 II,III species formed by these methods exhibit 55Mn hyperfine fields differing in magnitude by 9% (150 G), implying different Mn coordination environments induced by the electrolyte. The different ligand coordination observed in the enzyme (predominantly oxo and carboxylato) appears to be responsible for stabilization of the MnCatIII,III oxidation state as the resting state.
AB - Catalysts which functionally mimic the bacterial dimanganese catalase enzymes have been synthesized and their structure, electrochemical, redox, and EPR spectra have been compared to the enzyme. These compounds are formulated as [LMn2 II,IIX]Y2, μ-X = CH3CO2, ClCH2CO2; Y = ClO4, BPh4, CH3CO2, possessing a bridging μ-alkoxide from the ligand, HL = N,N,N',N'-tetrakis(2-methylenebenzimidazole)-1,3-diaminopropan-2-ol. An X-ray diffraction structure of [LMn2(CH3CO2)(butanol)] (C1O4)2·H2O, in the monoclinic space group P2(1)/c, confirmed the anticipated N6O septadentate coordination of the HL ligand, the bridging μ-acetate, and revealed both five- and six-coordinate Mn ions; the latter arising from a butanol solvent molecule. This contrasts with the six-coordinate Mn ions observed for the μ-Cl and μ-OH derivatives, LMn2Cl3 and LMn2(OH)Br2 (Mathur et al. J. Am. Chem. Soc. 1987, 109, 5227-5232). Like the enzyme, three electrons can be removed from these complexes to form four oxidation states ranging from Mn2 II,II to Mn2 III,IV. Three of these have been characterized by EPR and found to possess electronic ground states, MnIII electron orbital configurations, 55Mn hyperfine parameters, and Heisenberg exchange interactions analogous to those observed in the enzyme. For the μ-carboxylate derivatives electrochemistry reveals the initial oxidation process involves loss of two electrons at 0.81-0.86 V, forming Mn2 III,III, followed by dismutation to yield a Mn2 II,III and Mn2 III,IV species. By contrast, the μ-Cl and μ-OH derivatives oxidize by an initial one-electron process (0.49-0.54 V). For the μ-carboxylate derivatives chemical oxidation with Pb(OAc)4 also reveals an initial two-electron oxidation to a Mn2 III,III species, which dismutates to form both Mn2 II,III and Mn2 III,IV species. The two Mn2 II,III species formed by these methods exhibit 55Mn hyperfine fields differing in magnitude by 9% (150 G), implying different Mn coordination environments induced by the electrolyte. The different ligand coordination observed in the enzyme (predominantly oxo and carboxylato) appears to be responsible for stabilization of the MnCatIII,III oxidation state as the resting state.
KW - Catalase
KW - Electrochemical
KW - Enzyme
KW - EPR
KW - Hydrogen peroxide
KW - Manganese
KW - X-ray synthesis
UR - http://www.scopus.com/inward/record.url?scp=0027948056&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0027948056&partnerID=8YFLogxK
M3 - Article
AN - SCOPUS:0027948056
VL - 116
SP - 891
EP - 897
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 3
ER -