Kinetics and mechanism of the formation of FeII(edta)NO in the system FeII(edta)/NO/HONO/NO2- in aqueous solutions

Zang, V.; Kotowski, M.; Eldik, Rudi van

doi:10.1021/ic00292a007

Cited by 51 publications

(26 citation statements)

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“…For example, the oxidation kinetics of [Fe II (edta)] with molecular oxygen showed the same pH dependence. [21,22] But, moreover, kinetic studies of the reaction of [Fe II (edta)] with HONO or NO 2 Ϫ also showed the same pH dependence, [35,36] which supports our suggestion that the observed bell-shaped curves are due to the distribution of species in solution and not due to an acid-catalyzed process, as suggested in an earlier study. [21] [Fe II (cdta)] fitted with three exponential functions.…”

Section: Kinetic Measurementssupporting

confidence: 88%

Multistep Oxidation Kinetics of [FeII(cdta)] [cdta =N,N′,N′′,N′′′-(1,2-Cyclohexanediamine)tetraacetate] with Molecular Oxygen

Seibig¹,

Eldik²

1999

Eur. J. Inorg. Chem.

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The complicated oxidation kinetics of the reaction of [FeII(cdta)] [cdta = 1,2‐(N,N′‐ cyclohexanediamine)tetraacetate] with molecular oxygen was investigated as a function of [FeII], [O2], pH, temperature and pressure. In the presence of an excess of [FeII(cdta)] three steps could be observed, for which the following rate constants were found at 25°C; k1 = 1080 ± 16 M−1 s−1, k2 = 103 ± 4 M−1 s−1 and k3 = 59 ± 5 M−1 s−1. These reaction steps can be accounted for in terms of the following mechanism: (1) [FeII(cdta)H2O]2– reacts with O2 by a substitution process to form [FeII(cdta)O2]2–; (2) electron‐transfer to form an FeIII‐superoxo species; (3) subsequent bridge formation followed by electron‐transfer to give [(cdta)FeIII‐O22–‐FeIII(cdta)]4–; and (4) a fast decomposition of the peroxide intermediate yielding the monomeric [FeIII(cdta)] and H2O2. Rate and activation parameters for these steps are reported and discussed in terms of the postulated mechanism and in reference to available literature data.

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Section: Kinetic Measurementssupporting

confidence: 88%

Multistep Oxidation Kinetics of [FeII(cdta)] [cdta =N,N′,N′′,N′′′-(1,2-Cyclohexanediamine)tetraacetate] with Molecular Oxygen

Seibig¹,

Eldik²

1999

Eur. J. Inorg. Chem.

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“…As Zang et al . () showed that reaction rates increased at lower pH, similar experiments were carried out at pH 6.5 and 7.5. In experiments with ca.…”

Section: Resultssupporting

confidence: 59%

“…Zang et al . () showed that the reaction of Fe(II)‐EDTA under anoxic conditions with an excess of nitrite produces Fe(III)‐EDTA and Fe(II)‐EDTA‐NO in a 1:1 ratio (equation ).

\begin{matrix} 2 {[Fe(II)‐EDTA]}^{2 -} + {NO}_{2}^{-} + 2 {normalH}^{+} \to {[Fe(II)‐EDTA‐NO]}^{2 -} \\ + {Fe(III)‐EDTA}^{-} + {normalH}_{2} O \end{matrix}

…”

Section: Discussionmentioning

confidence: 99%

“…As part of their studies, they presented evidence that Fe(II)‐EDTA is not oxidized abiotically by nitrite and therefore concluded that all oxidized Fe(II) must originate from direct enzymatic activity. However, the absence of Fe(II)‐EDTA oxidation by nitrite in their work differed from the results of other studies that have shown chemical oxidation of Fe(II)‐EDTA by nitrite and NO (Zang et al ., ; Van Der Maas et al ., ; Kumaraswamy et al ., ). It should be noted that some of these other studies measured Fe(II) concentrations with ferrozine as the colorimetric agent (Stookey, ) to follow Fe(II)‐EDTA oxidation, while others used phenanthroline as the colorimetric complexant (Tamura et al ., ).…”

Section: Introductionmentioning

confidence: 97%

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Oxidation of Fe(II)‐EDTA by nitrite and by two nitrate‐reducing Fe(II)‐oxidizing Acidovorax strains

et al. 2015

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The enzymatic oxidation of Fe(II) by nitrate-reducing bacteria was first suggested about two decades ago. It has since been found that most strains are mixotrophic and need an additional organic co-substrate for complete and prolonged Fe(II) oxidation. Research during the last few years has tried to determine to what extent the observed Fe(II) oxidation is driven enzymatically, or abiotically by nitrite produced during heterotrophic denitrification. A recent study reported that nitrite was not able to oxidize Fe(II)-EDTA abiotically, but the addition of the mixotrophic nitrate-reducing Fe(II)-oxidizer, Acidovorax sp. strain 2AN, led to Fe(II) oxidation (Chakraborty & Picardal, 2013). This, along with other results of that study, was used to argue that Fe(II) oxidation in strain 2AN was enzymatically catalyzed. However, the absence of abiotic Fe(II)-EDTA oxidation by nitrite reported in that study contrasts with previously published data. We have repeated the abiotic and biotic experiments and observed rapid abiotic oxidation of Fe(II)-EDTA by nitrite, resulting in the formation of Fe(III)-EDTA and the green Fe(II)-EDTA-NO complex. Additionally, we found that cultivating the Acidovorax strains BoFeN1 and 2AN with 10 mM nitrate, 5 mm acetate, and approximately 10 mM Fe(II)-EDTA resulted only in incomplete Fe(II)-EDTA oxidation of 47-71%. Cultures of strain BoFeN1 turned green (due to the presence of Fe(II)-EDTA-NO) and the green color persisted over the course of the experiments, whereas strain 2AN was able to further oxidize the Fe(II)-EDTA-NO complex. Our work shows that the two used Acidovorax strains behave very differently in their ability to deal with toxic effects of Fe-EDTA species and the further reduction of the Fe(II)-EDTA-NO nitrosyl complex. Although the enzymatic oxidation of Fe(II) cannot be ruled out, this study underlines the importance of nitrite in nitrate-reducing Fe(II)- and Fe(II)-EDTA-oxidizing cultures and demonstrates that Fe(II)-EDTA cannot be used to demonstrate unequivocally the enzymatic oxidation of Fe(II) by mixotrophic Fe(II)-oxidizers.

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“…Known intracellular targets include enzymes containing haem and Fe-S centres, such as guanylate cyclase [33] and lipoxygenase [34]. NO' also forms stable complexes with inorganic iron [35], and relatively stable nitrosothiols and nitrosamines on proteins [36, 371. Any of these events might influence oxidative events either in the medium or within the cells. We are presently investigating these possibilities.…”

Section: +Pmamentioning

confidence: 99%

Cellular modification of low-density lipoproteins

Jessup

1993

Biochemical Society Transactions

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Kinetics and mechanism of the formation of FeII(edta)NO in the system FeII(edta)/NO/HONO/NO2- in aqueous solutions

Cited by 51 publications

References 1 publication

Multistep Oxidation Kinetics of [FeII(cdta)] [cdta =N,N′,N′′,N′′′-(1,2-Cyclohexanediamine)tetraacetate] with Molecular Oxygen

Multistep Oxidation Kinetics of [FeII(cdta)] [cdta =N,N′,N′′,N′′′-(1,2-Cyclohexanediamine)tetraacetate] with Molecular Oxygen

Oxidation of Fe(II)‐EDTA by nitrite and by two nitrate‐reducing Fe(II)‐oxidizing Acidovorax strains

Cellular modification of low-density lipoproteins

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