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Nitric oxide (NO) : a universal regulator of an organism’s vital processes at the cellular level

Pedrycz A., Siermontowski P., Ciechan A., Orłowski M., Zając G.

Polish Hyperbaric Research

2013

nr 2(43)

93--103

At the present time, seven types of nitrogen oxide have been discovered and defined: Nitrogen oxide (I) (N2O) – nitrous oxide, also known as a laughing gas, Nitric oxide (II) (NO) – nitrogen monoxide, Nitrogen oxide (III) (N2O3), Nitrogen oxide (IV) (NO2) – nitrogen dioxide which may produce a dimer – N2O4 – dinitrogen tetroxide, Nitrogen oxide (V) (N2O5) – dinitrogen pentoxide, Nitrogen oxide (VI) (NO3) nitrogen trioxide – nitrate radical of a strong oxidizing effect, Nitrogen oxide (VII) (N2O6) – dinitrogen hexoxide – an unstable compound with a peroxide bond O2N-O-ONO2. Of the above compounds the one that is of the greatest significance from the point of view of medicine is nitric oxide (NO), hence it is the main focus of this work.

Do chwili obecnej odkryto i opisano 7 tlenków azotu: Tlenek azotu (I) (N2O)- podtlenek azotu, tlenek di azotu, inaczej zwany gazem rozweselającym, Tlenek azotu (II) (NO) - monotlenek azotu, Tlenek azotu (III) (N2O3), Tlenek azotu IV (NO2) - dwutlenek azotu, który może tworzyć dimer- N2O 4 - czterotlenek azotu, Tlenek azotu (V) (N2O5) pięciotlenek di azotu, Tlenek azotu (VI) (NO3) trójtlenek azotu- rodnik azotanowy o silnym działaniu utleniającym, Tlenek azotu (VII) (N2O6)- sześciotlenek azotu - nietrwały związek z wiązaniem nadtlenkowym O2N-O-O-NO2. W medycynie największe znaczenie ma monotlenek azotu (NO) i jemu poświęcona jest niniejsza praca.

Nadtlenoazotyn - silny biologiczny utleniacz

Bijak M., Ponczek M. B., Saluk J., Chabielska M., Stępniak J., Nowak P.

Wiadomości Chemiczne

2012

[Z] 66, 7-8

623-635

As demonstrated in recent years, one of the major factors of oxidative stress, generated in the circulatory system, in both acute and chronic pathological conditions, is peroxynitrite (ONOO –) [4]. Peroxynitrite is a strong biological oxidant and nitrating compound, generated in vivo from a rapid reaction of two relatively less reactive, but commonly found, of free radicals: nitrogen monoxide (NO ) and superoxide (O2–) [8]. This reaction occurs spontaneously and is not catalyzed by any enzyme. A fundamental reaction of ONOO – in biological systems is its fast reaction with carbon dioxide (k = 5,7 ź 104 M–1 s–1) and yields a short-lived intermediate, nitrosoperoxycarbonate (ONOOCO 2 –), which homolyzes leads to the formation of carbonate (CO 3–) and nitrogen dioxide (NO 2) radicals (yield ~35%) [29, 30] (Fig. 1), which are one-electron oxidants. ONOO – is responsible for oxidative modifications in a wide variety of biomolecules and is capable to induce of nitrative changes in sulfur and aromatic amino acids, especially 3-nitrotyrosine and dityrosine formation [17] (Fig. 2). This article describes the formation, reactivity and biological action of peroxynitrite.

Oxidation of Hexacyanoferrate(II) by Peroxynitrite. A Mechanistic and Kinetic Study

Martinez E., Mucientes A., Poblete F., Rodriguez A.

Polish Journal of Chemistry

2004

Vol. 78 / nr 2

261-271

Akinetic study of the oxidation of hexacyanoferrate(II) by peroxynitrite has been carried out, using a stopped-flow technique. The variation of the experimental rate constant over a wide concentration range of Fe(CN)6 4 has been investigated under different experimental conditions in terms of pH, ionic strength and temperature. Acorrelation between kexp and the substrate concentration has been obtained and this shows first-order behavior in substrate at high concentrations of Fe(CN)6 4 .Areaction mechanism is proposed, in which the hexacyanoferrate(II) reacts in competitive pathways with the peroxynitrous acid (direct oxidation) and with HOź and źNO2 radicals formed in the homolysis of the peroxide bond ofHOONO(indirect oxidation). Moreover, two individual constants, kc (the formation constant of the germinated radical pair [HOź źNO2]) and k7 (direct oxidation constant), have been evaluated together with the thermodynamic parameters of these elementary steps.