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Mechanism of peroxynitrite interaction with cytochrome c.

100%

Gębicka L., Didik J.

2003

vol. 50

issue 3

815-823

Kinetics of the reaction of peroxynitrite with ferric cytochrome c in the absence and presence of bicarbonate was studied. It was found that the heme iron in ferric cytochrome c does not react directly with peroxynitrite. The rates of the absorbance changes in the Soret region of cytochrome c spectrum caused by peroxynitrite or peroxynitrite/bicarbonate were the same as the rate of spontaneous isomerization of peroxynitrite or as the rate of the reaction of peroxynitrite with bicarbonate, respectively. This means that intermediate products of peroxynitrite decomposition, ·OH/·NO2 or, in the presence of bicarbonate, CO3-·/·NO2, are the species responsible for the absorbance changes in the Soret band of cytochrome c. Modifications of the heme center of cytochrome c by radiolytically produced radicals, ·OH, ·NO2 or CO3-·, were also studied. The absorbance changes in the Soret band caused by radiolytically produced ·OH or CO3-· were much more significant that those observed after peroxynitrite treatment, compared under similar concentrations of radicals. ·NO2 produced radiolytically did not interact with the heme center of cytochrome c. Cytochrome c exhibited an increased peroxidase-like activity after reaction with peroxynitrite as well as with radiolytically produced ·OH, ·NO2 or CO3-· radicals. This means that modification of protein structure: oxidation of amino acids and/or tyrosine nitration, facilitates reaction of H2O2 with the heme iron of cytochrome c, followed by reaction with the second substrate.

Physico chemical properties of irradiated i-SANEX diluents

75%

Mossini E., Macerata E., Giola M., Brambilla L., Castiglioni C., Mariani M.

issue 4

893-898

The development of effective processes to recover minor actinides from spent nuclear fuel cannot leave out of consideration the evaluation of the impact of ionizing radiations on safety, fluid dynamics and extraction efficiency. It is common knowledge from the literature that radiation damage mainly affects the diluents and, indirectly, the extractants [1], but a lack of knowledge remains regarding the radiolytic behavior of innovative selective actinide extraction (i-SANEX) diluents [2, 3]. As natural prosecution of the work already performed on diluted nitric acid solutions [4], 0.44 M nitric acid solutions were irradiated in contact with a mixture of kerosene + 5 vol.% 1-octanol by a Co-60 source at 2.5 kGy/h dose rate and up to 100 kGy absorbed dose, conditions of interest for the future industrial facility. Density, viscosity, acidity, nitrate anion concentration and phase transfers were systematically measured before and after γ-irradiation. This was performed because radiation-induced modifications of these parameters may induce alterations of both the fluid dynamics and the separation performances of the extracting system. The results suggest that the fluid-dynamics of the system should be unaltered. In fact, only slight alterations of the organic phase viscosity and of the aqueous phase acidity were measured after irradiation, suggesting the occurrence of limited phase transfers and of diluent by-products formation.

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1 Acta Biochimica Polonica

1 Nukleonika

1 2015

1 2003

1 Brambilla L.

1 Castiglioni C.

1 Didik J.

1 Giola M.

1 Gębicka L.

1 Macerata E.

1 Mariani M.

1 Mossini E.

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Mechanism of peroxynitrite interaction with cytochrome c.

Physico chemical properties of irradiated i-SANEX diluents