The Kinetics of the Interaction Between Iron(III)-Ethylenediaminetetraacetate and Peroxynitrite

Abstract

The kinetics of the formation of the purple-colored species between Fe III -EDTA and peroxynitrite were studied as a function of pH (10.4-12.3) at 22°C in aqueous solutions using a stopped-flow technique. A purple-colored species was immediately formed upon mixing, which had an absorbance maximum at 520 nm. The increase in absorbance with time could be fit empirically by a power function with two parameters a and b. The power equation determined was absorbance = a*t b , where a increased linearly with pH and the concentration of peroxynitrite, while b almost remained constant with a value of *0.25. The molar extinction coefficient e 520 nm for the colored species was determined as 13 M -1 cm -1 , which is much lower than e 520 nm = 520 M -1 cm -1 for the [Fe III (EDTA)O 2 ] 3-, a purple species observed in the Fe III -EDTA-H 2 O 2 system. The results of kinetics and spectral measurements of the present study are briefly discussed and compared with those of the reaction between Fe(III)-EDTA and hydrogen peroxide.

Reactive Inorganic Oxy‐Species of C, N, S, and P

“…The reaction between Fe(III)EdTA and peroxynitrite immediately formed a purple-colored species with an absorption maximum at 520 nm, similar to species obtained in the Fe(III)EdTA/H 2 O 2 system in an alkaline medium [257][258][259][260]. This species may be an end-on peroxynitrite complex because of much lower absorptivity compared to the peroxo-complex species [257]. The rate of the reaction between Fe(III)EdTA and peroxynitrite increased rapidly and slowed down with increasing concentration of peroxynitrite.…”

“…Recently, the kinetics and spectral measurements on the Fe(III)EdTA/ peroxynitrite system as a function of pH (10.4-12.3) at 25°C in aqueous solution were made [257]. The reaction between Fe(III)EdTA and peroxynitrite immediately formed a purple-colored species with an absorption maximum at 520 nm, similar to species obtained in the Fe(III)EdTA/H 2 O 2 system in an alkaline medium [257][258][259][260].…”

Pro-oxidative effect of peroxynitrite regarding biological systems: a special focus on high-molar-mass hyaluronan degradation

“…As reported (Ducrocq et al 1999), transition metals including Fe(III)-EDTA and Cu/Zn-SOD can catalyze peroxynitrite-mediated nitration of phenolic compounds. The kinetic study of Fe(III)-EDTA-ONOO -and Fe(III)-EDTA-H 2 O 2 model systems formation, as a function of pH, was used with the aim to elucidate the iron speciation in natural waters as well as to understand the mechanism of oxygen activation by iron containing proteins (Sharma et al 2010). …”

Mössbauer study of peroxynitrito complex formation with FeIII-chelates

“…It was observed that the UV-visible spectrum of this reaction product is the same as that of the dihapto-peroxo complex [(EDTA)Fe III (η 2 -O 2 )] 3− , while the molar extinction coefficients significantly differ [2].…”