103384-30-1Relevant articles and documents
Nitrite reduction mediated by heme models. Routes to NO and HNO?
Heinecke, Julie L.,Khin, Chosu,Pereira, Jose Clayston Melo,Suárez, Sebastián A.,Iretskii, Alexei V.,Doctorovich, Fabio,Ford, Peter C.
, p. 4007 - 4017 (2013)
The water-soluble ferriheme model FeIII(TPPS) mediates oxygen atom transfer from inorganic nitrite to a water-soluble phosphine (tppts), dimethyl sulfide, and the biological thiols cysteine (CysSH) and glutathione (GSH). The products with the latter reductant are the respective sulfenic acids CysS(O)H and GS(O)H, although these reactive intermediates are rapidly trapped by reaction with excess thiol. The nitrosyl complex FeII(TPPS)(NO) is the dominant iron species while excess substrate is present. However, in slightly acidic media (pH ≈ 6), the system does not terminate at this very stable ferrous nitrosyl. Instead, it displays a matrix of redox transformations linking spontaneous regeneration of FeIII(TPPS) to the formation of both N2O and NO. Electrochemical sensor and trapping experiments demonstrate that HNO (nitroxyl) is formed, at least when tppts is the reductant. HNO is the likely predecessor of the N2O. A key pathway to NO formation is nitrite reduction by FeII(TPPS), and the kinetics of this iron-mediated transformation are described. Given that inorganic nitrite has protective roles during ischemia/reperfusion (I/R) injury to organs, attributed in part to NO formation, and that HNO may also reduce net damage from I/R, the present studies are relevant to potential mechanisms of such nitrite protection.
Water-Soluble Nitroxyl Porphyrin Complexes FeIITPPSHNO and FeIITPPSNO- Obtained from Isolated FeIITPPSNO·
Mazzeo, Agostina,Pellegrino, Juan,Doctorovich, Fabio
supporting information, p. 18521 - 18530 (2019/11/21)
The first biomimetic water-soluble FeII-porphyrin nitroxyl complexes were obtained and characterized by UV-vis in protonated and deprotonated forms by reduction of previously isolated and characterized FeIITPPSNO·. The pKa involved in the FeII-HNO → FeII-NO- + H+ equilibrium was estimated to be around 9.7. The FeIITPPSHNO complex spontaneously reoxidizes to the nitrosyl form following a first-order kinetic decay with a measured kinetic constant of k = 0.017 s-1. Experiments show that the HNO adduct undergoes unimolecular homolytic cleavage of the H-NO bond. DFT calculations suggest a phlorin radical intermediate for this reaction. The deprotonated NO- complex resulted to be more stable, with a half-life of about 10 min.
Photochemistry of nitric oxide adducts of water-soluble iron(III) porphyrin and ferrihemoproteins studied by nanosecond laser photolysis
Hoshino, Mikio,Ozawa, Koji,Seki, Hiroshi,Ford, Peter C.
, p. 9568 - 9575 (2007/10/02)
Water-soluble iron(III) porphyrin and ferrihemoproteins (methemoglobin, metmyoglobin, oxidized cytochrome c, and catalase) associate with NO to yield the nitric oxide adducts. The equilibrium constants for association of ferrihemoproteins and NO are 1 order of magnitude larger than that of the water-soluble iron(III) porphyrin which is free from protein, suggesting that the proteins offset the forward and backward reaction rates in the equilibrium reactions. Nanosecond laser photolysis studies of the nitric oxide adducts of metmyoglobin, oxidized cytochrome c, and catalase, (NO)MbIII, (NO)CytIII, and (NO)CatIII, have been carried out. The transient detected after laser flash photolysis of (NO)CatIII is identified as CatIII. However, the transients observed for (NO)MbIII and (NO)CytIII at 50 ns after laser pulsing are ascribed to MbIIItr and CytIIItr, respectively, with the absorption spectra different from those of uncomplexed MbIII and CytIII. In particular, the absorption spectrum of CytIIItr markedly differs from that of the uncomplexed CytIII. The species MbIIItr and CytIIItr are found to change to MbIII and CytIII, respectively, within a few microseconds. The quantum yields for the photodissociation of NO from nitric oxide adducts of ferrihemoproteins are 1 order of magnitude less than that from the NO adduct of the water-soluble iron(III) porphyrin, probably due to fast geminate recombination reaction of NO and ferrihemoprotein in a heme pocket. The photochemistry of the nitric oxide adducts of hemoproteins and water-soluble iron(II) porphyrin is also described on the basis of laser phosolysis studies.
