Kinetics and mechanism of the forward and reverse reactions between N,N′-dimethyl-4,4′-bipyridinium and hexacyanoferrate(II)

The kinetics of the hexacyanoferrate(III)-N,N′-dimethyl-4,4′-bipyridinium radical (MV+) reaction was studied by a laser flash photolysis technique. The radical was generated, in the presence of Fe(CN)6 3-, by quenching the excited state *Ru(bpy)3 2+ with MV2+. The second-order rate constant for the Fe(CN)6 3--MV+ reaction is (7.6 ± 0.5) × 109 M-1 s-1 at 23°C and ionic strength 0.10 M. Comparison with the rate constants calculated for the diffusion-controlled reaction (4.7 × 109 M-1 s-1) and the activation-controlled reaction (5.2 × 1012 M-1 s-1, on the basis of self-exchange rate constants of 8.0 × 105 M-1 s-1 and 1.9 × 104 M-1 s-1 for the MV2+/+ and Fe(CN)6 3-/4- couples, respectively) leads to the conclusion that the Fe(CN)6 3--MV+ reaction is diffusion controlled. The rate constant for the Fe(CN)6-MV2+ reaction, calculated from the rate constant for the Fe(CN)6 3--MV+ reaction and the appropriate equilibrium constant, is 2.4 × 10-5 M-1 s-1 at 23°C and ionic strength 0.10 M. Microscopic reversibility considerations require that the Fe(CN)6 4--MV2+ reaction be controlled by the dissociation of the successor complex Fe(CN)6 3-|MV+. The thermal and optical electron transfers in the ion pair Fe(CN)6 4-|MV2+ and in related systems are analyzed and discussed. © 1982 American Chemical Society.

The role of chemokines and chemokine receptors in eosinophil activation during inflammatory allergic reactions

Chemokines are important chemotactic cytokines that play a fundamental role in the trafficking of leukocytes to sites of inflammation. They are also potent cell-activating factors, inducing cytokine and histamine release and free radical production, a fact that makes them particularly important in the pathogenesis of allergic inflammation. The action of chemokines is regulated at the level of agonist production and processing as well as at the level of receptor expression and coupling. Therefore, an analysis of the ligands must necessarily consider receptors. Eosinophils are target cells involved in the allergic inflammatory response since they are able to release a wide variety of mediators including CC and CXC chemokines and express their receptors. These mediators could damage the airway epithelial cells and might be important to stimulate other cells inducing an amplification of the allergic response. This review focuses on recently emerging data pertaining to the importance of chemokines and chemokine receptors in promoting eosinophil activation and migration during the allergic inflammatory process. The analysis of the function of eosinophils and their chemokine receptors during allergic inflammation might be a good approach to understanding the determinants of asthma severity and to developing novel therapies.

Re-examination of the anion derivatives of isoflavones by radical fragmentation in negative electrospray ionization tandem mass spectrometry: experimental and computational studies

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Dinitrosyl iron complexes with cysteine. kinetics studies of the formation and reactions of dnics in aqueous solution

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)