Fascinating inorganic/bioinorganic reaction mechanisms

Eldik, Rudi van

doi:10.1016/j.ccr.2007.02.004

Cited by 62 publications

(16 citation statements)

References 22 publications

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“…The very high reactivity of the latter was confirmed in numerous biomimetic and enzyme studies with application of synthetic iron(III) porphyrins and thermophilic P450 isolated from Sulfolobus acidocaldarius, respectively. [1][2][3] However, the transient character and high instability of the reactive intermediates in the catalytic cycle of P450 enzymes hamper their trapping and direct characterisation under physiological conditions. Therefore, there is still a debate on the nature of the reactive intermediate(s) responsible for substrate oxidation.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Insight into Peroxo‐Shunt Formation of Biomimetic Models for Compound II, Their Reactivity toward Organic Substrates, and the Influence of N‐Methylimidazole Axial Ligation

Oszajca¹,

Drzewiecka-Matuszek²,

Franke³

et al. 2014

Chemistry A European J

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High-valent iron-oxo species have been invoked as reactive intermediates in catalytic cycles of heme and nonheme enzymes. The studies presented herein are devoted to the formation of compound II model complexes, with the application of a water soluble (TMPS)Fe(III)(OH) porphyrin ([meso-tetrakis(2,4,6-trimethyl-3-sulfonatophenyl)porphinato]iron(III) hydroxide) and hydrogen peroxide as oxidant, and their reactivity toward selected organic substrates. The kinetics of the reaction of H2O2 with (TMPS)Fe(III)(OH) was studied as a function of temperature and pressure. The negative values of the activation entropy and activation volume for the formation of (TMPS)Fe(IV)=O(OH) point to the overall associative nature of the process. A pH-dependence study on the formation of (TMPS)Fe(IV)=O(OH) revealed a very high reactivity of OOH(-) toward (TMPS)Fe(III)(OH) in comparison to H2O2. The influence of N-methylimidazole (N-MeIm) ligation on both the formation of iron(IV)-oxo species and their oxidising properties in the reactions with 4-methoxybenzyl alcohol or 4-methoxybenzaldehyde, was investigated in detail. Combined experimental and theoretical studies revealed that among the studied complexes, (TMPS)Fe(III)(H2O)(N-MeIm) is highly reactive toward H2O2 to form the iron(IV)-oxo species, (TMPS)Fe(IV)=O(N-MeIm). The latter species can also be formed in the reaction of (TMPS)Fe(III)(N-MeIm)2 with H2O2 or in the direct reaction of (TMPS)Fe(IV)=O(OH) with N-MeIm. Interestingly, the kinetic studies involving substrate oxidation by (TMPS)Fe(IV)=O(OH) and (TMPS)Fe(IV)=O(N-MeIm) do not display a pronounced effect of the N-MeIm axial ligand on the reactivity of the compound II mimic in comparison to the OH(-) substituted analogue. Similarly, DFT computations revealed that the presence of an axial ligand (OH(-) or N-MeIm) in the trans position to the oxo group in the iron(IV)-oxo species does not significantly affect the activation barriers calculated for C-H dehydrogenation of the selected organic substrates.

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Section: Introductionmentioning

confidence: 99%

Mechanistic Insight into Peroxo‐Shunt Formation of Biomimetic Models for Compound II, Their Reactivity toward Organic Substrates, and the Influence of N‐Methylimidazole Axial Ligation

Oszajca¹,

Drzewiecka-Matuszek²,

Franke³

et al. 2014

Chemistry A European J

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“…Only the intrinsic component that arises from changes in bond lengths and angles contributes to the volume of activation, which can be considered as a direct measure for the degree of bond formation or breakage in the transition state. [22,24,25] The values for the activation volume were extracted by analyzing the data of the variable pressure 17 O NMR measurements with Eqn (5), where the pressure dependence of k ex was expressed according to Eqn (6).…”

Section: Resultsmentioning

confidence: 99%

The impact of tripodal chelates on water exchange kinetics and mechanisms: A variable temperature and pressure 17O NMR study to clarify the structure-reactivity relationship in [FeII(L)(H2O)2]− complexes

et al. 2008

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The effect of temperature and pressure on the water exchange reaction of [Fe(II)(NTA)(H2O)2](-) and [Fe(II)(BADA)(H2O)2](-) (NTA = nitrilotriacetate; BADA = beta-alanindiacetate) was studied by 17O NMR spectroscopy. The [Fe(II)(NTA)(H2O)2](-) complex showed a water exchange rate constant, k(ex), of (3.1 +/- 0.4) x 10(6) s(-1) at 298.2 K and ambient pressure. The activation parameters DeltaH( not equal), DeltaS( not equal) and DeltaV( not equal) for the observed reaction are 43.4 +/- 2.6 kJ mol(-1), + 25 +/- 9 J K(-1) mol(-1) and + 13.2 +/- 0.6 cm(3) mol(-1), respectively. For [Fe(II)(BADA)(H2O)2](-), the water exchange reaction is faster than for the [Fe(II)(NTA)(H2O)2](-) complex with k(ex) = (7.4 +/- 0.4) x 10(6) s(-1) at 298.2 K and ambient pressure. The activation parameters DeltaH( not equal), DeltaS( not equal) and DeltaV( not equal) for the water exchange reaction are 40.3 +/- 2.5 kJ mol(-1), + 22 +/- 9 J K(-1) mol(-1) and + 13.3 +/- 0.8 cm(3) mol(-1), respectively. The effect of pressure on the exchange rate constant is large and very similar for both systems, and the numerical values for DeltaV( not equal) suggest in both cases a limiting dissociative (D) mechanism for the water exchange process.

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“…Os metais tendem a perder elétrons facilmente formando íons com cargas positivas, solúveis em fluidos biológicos. É na forma catiônica que os metais desempenham suas principais funções biológicas (van Eldik, 2007). Enquanto íons metálicos apresentam-se deficientes de elétrons, biomoléculas como proteínas e DNA são ricas em elétrons e a atração entre estas cargas opostas garante a interação entre íons metálicos e moléculas biológicas.…”

Section: Discussionunclassified

Efeito Mutagênico do Edetato de Cobre ([Cu(EDTA)]-2) Livre e Nanoencapsulado em Camundongos e Peixes

Jacacobowski¹,

Zobiole²,

Padilha³

et al. 2013

Ecotoxicol. Environ. Contam.

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ResumoEstudos recentes demonstram que o cobre complexado com o ácido etilenodiaminotetracético, ([Cu(EDTA)] -2 ), apresenta letalidade sobre larvas de Aedes aegypti. Este composto pode ter uma liberação lenta e gradativa quando complexado em nanocápsulas de goma/gelatina/quitosana, o que pode limitar sua toxicidade para o ambiente. No entanto, a genotoxicidade do [Cu(EDTA)] -2 ainda não está totalmente elucidada. Para avaliar o potencial mutagênico do [Cu(EDTA)] -2 , analisamos a frequência de micronúcleos no sangue periférico de camundongos e peixes submetidos a [Cu(EDTA)] -2 livre e nanoencapsulado. A carcaça dos peixes foi avaliada por espectrometria de massa para quantificar o cobre tecidual. Em camundongos a frequência de micronúcleos nos animais expostos ao [Cu(EDTA)] -2 na forma livre foi significativamente maior em relação aos animais submetidos à forma nanoencapsulada. Em peixes, somente o [Cu(EDTA)] -2 livre foi capaz de induzir aumento na frequência de micronúcleos. A análise espectrométrica demonstrou acúmulo de íons cobre no fígado nos grupos de peixes estudados, com diferença significativa em relação ao grupo controle. Nas brânquias dos peixes não foram observadas diferenças na concentração de cobre entre os grupos e ainda, o conteúdo de cobre foi significativamente menor em relação ao encontrado no fígado. Os resultados sugerem que o [Cu(EDTA)] -2 livre pode induzir efeitos mutagênicos em mamíferos, porém o nanoencapsulamento parece conferir maior segurança ao produto devido a sua liberação mais lenta.Palavras-chave: Camundongos; Edetato de Cobre; Mutagenicidade; Nanocápsulas; Peixes; Teste do Micronúcleo. The mutagenic effect of the free and nanoencapsulated Cooper edetate in mice and fish AbstractRecent studies show that copper complexes with ethylenediaminetetraacetic acid ([Cu(EDTA)] -2 ), is lethal for Aedes aegypti larvae. This compound may have a controlled release when nanocapsules complex in gum/gelatin/chitosan, which may limit their toxicity to the environment. However, the genotoxicity of [Cu(EDTA)] -2 is not fully elucidated. To assess the mutagenic potential of [Cu(EDTA)] -2 , we analyzed the frequency of micronuclei in peripheral blood of mice and fish subjected to free and nanoencapsulated [Cu(EDTA)] -2 . The carcass of the fish was assessed by mass spectrometry to measure tissue copper. In mice, the frequency of micronuclei in animals exposed to free [Cu(EDTA)] -2 was significantly higher in the animals submitted to the nanoencapsulated form. In fish, only the free [Cu(EDTA)] -2 was able to induce increased frequency of micronuclei. Mass spectrometric analysis showed copper accumulation in the fish's liver studied, with significant difference in the control. In the gills of fish were not observed differences in copper concentration between the groups and the copper content was significantly lower than that found in the liver. The results suggest that free [Cu(EDTA)] -2 can induce mutagenic effects in mammals, but the nanoencapsulated seems to give more security to the product due ...

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Fascinating inorganic/bioinorganic reaction mechanisms

Cited by 62 publications

References 22 publications

Mechanistic Insight into Peroxo‐Shunt Formation of Biomimetic Models for Compound II, Their Reactivity toward Organic Substrates, and the Influence of N‐Methylimidazole Axial Ligation

Mechanistic Insight into Peroxo‐Shunt Formation of Biomimetic Models for Compound II, Their Reactivity toward Organic Substrates, and the Influence of N‐Methylimidazole Axial Ligation

The impact of tripodal chelates on water exchange kinetics and mechanisms: A variable temperature and pressure 17O NMR study to clarify the structure-reactivity relationship in [FeII(L)(H2O)2]− complexes

Efeito Mutagênico do Edetato de Cobre ([Cu(EDTA)]-2) Livre e Nanoencapsulado em Camundongos e Peixes

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