- Kinetic characterisation of o-aminophenols and aromatic o-diamines as suicide substrates of tyrosinase
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We study the suicide inactivation of tyrosinase acting on o-aminophenols and aromatic o-diamines and compare the results with those obtained for the corresponding o-diphenols. The catalytic constants follow the order aromatic o-diamines max/KmS, follows this order: o-diphenols > o-aminophenols > aromatic o-diamines.
- Munoz-Munoz, Jose Luis,Garcia-Molina, Francisco,Berna, Jose,Garcia-Ruiz, Pedro Antonio,Varon, Ramon,Tudela, Jose,Rodriguez-Lopez, Jose N.,Garcia-Canovas, Francisco
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experimental part
p. 647 - 655
(2012/08/08)
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- A green method for the electroorganic synthesis of new 1,3-indandione derivatives
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This is an environmentally friendly method in the field of electroorganic reactions under controlled potential electrolysis, without toxic reagents at a carbon electrode in an undivided cell which involves the (EC) mechanism reaction and comprises two ste
- Moghaddam, Abdolmajid Bayandori,Ganjali, Mohammad Reza,Norouzi, Parviz,Latifi, Maryam
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p. 1391 - 1396
(2007/10/03)
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- Bridged fluorescent dyes, their preparation and their use in assays
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Bridged fluorescent dyes of the cyanine and squaraine families are disclosed. The dyes are useful as markers in assay techniques and offer advantages of undergoing excitation at a common wavelength but emitting at structure dependent different wavelengths.
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- Oxidation of benzenediols by hexabromoiridate(IV): Kinetics at ambient and elevated pressures
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The kinetics of oxidation of several benzenediols by the hexabromoiridate(IV) ion have been studied spectrophotometrically by the stopped-flow method. In 0.010 mol dm-3 HClO4 and an ionic strength of 0.10 mol dm-3 (NaClO4) at 25.0°C the second-order rate constants (the reaction is first order in each reactant concentration), vary from 1.26 × 102 to 9.3 × 104 dm3 mol-1 s-1. The enthalpies of activation range from about 44 kJ mol-1 for the slowest reacting substrate to about 20 kJ mol-1 for the faster reactions. The ΔS? values do not vary over a wide range; the reaction rates are governed more by the enthalpy barrier. Application of pressure (up to 125 MPa) causes significant rate accelerations, giving rise to ΔV? values in the -17 to -26 cm3 mol-1 range, consistent with the large, negative ΔS? values. This indicates that the rate limiting step is largely characterised by an increase in species ordering and electrostriction, and in the present case slightly less than for the corresponding reactions with the less bulky hexachloroiridate(IV) ion.
- Ciosto, Cornelia,Bajaj, Hari C.,Van Eldik, Rudi,Hubbard, Colin D.
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p. 1503 - 1507
(2007/10/03)
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- Kinetics of the Oxidation of Ascorbic Acid and Substituted 1,2- and 1,4-Dihydroxybenzenes by the Hexacyanoruthenate(III) Ion in Acidic Perchlorate Media
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The kinetics of oxidation of ascorbic acid and a series of substituted 1,2- and 1,4-dihydroxybenzene compounds (H2Q) by 3- have been investigated in acidic perchlorate media.The inverse dependences of the rate constants on acid concentrations for 2,3-dicyano-1,4-dihydroxybenzene, 4,5-dihydroxybenzene-1,3-disulphonate, and ascorbic acid have been attributed to concurrent rate-determining pathways involving the one-electron oxidations of H2Q or HQ(-) by 3- to the corresponding semiquinone or ascorbate radical intermediate.The cross-reaction rate constants have been correlated with the semiquinone or ascorbate reduction potentials in terms of the Marcus relationship to yield a 3--4- electron self-exchange rate constant of (1.0 +/- 0.8) . 105 dm3mol-1s-1.This is compared with those for other low-spin d5-d6 transition-metal complex couples and discussed in terms of the inner-sphere and solvent reorganization energies.
- Hoddenbagh, J. Mark A.,Macartney, Donal H.
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p. 615 - 620
(2007/10/02)
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- Kinetics and mechanism of the oxidation of 2,3-dihydroxybenzoic acid by iron(III)
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The kinetics of the oxidation of 2,-3-dihydroxybenzoic acid (DHB) by aqueous iron(III) have been studied in aqueous acid with [Fe(III)] ? [DHB]. The initial complexation reaction of Fe(OH2)63+ and DHB was studied previously. The iron(III)-DHB complex is oxidized by iron(III) with a rate law that is first order in iron(III) and has terms that are inverse first order in [H+] and inverse second order in [Fe(OH2)62+]. It is shown that the oxidation does not proceed by simple intramolecular electron transfer within the iron(III)-DHB complex. A mechanism is proposed in which the latter complex reacts first by substitution on free iron(III) followed by two reversible electron-transfer steps to give the quinone product.
- Xu, Jinhuang,Jordan
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p. 4563 - 4566
(2008/10/08)
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- Mechanisms of Reduction of trans-Cyclohexane-1,2-diamine-NNN'N'-tetra-acetatomanganate(III) by Hydrazine, Hydroxylamine, and Substituted Benzene-1,2-diols
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The kinetics and mechanism of reduction of trans-cyclohexane-1,2-diamine-NNN'N'-tetra-acetatomanganate(III), III(cdta)(H2O)>-, by hydrazine hydroxylamine, and a series of substituted benzene-1,2-diols C6H3(OH)2R (R=H, 4-Me, 4-CO2H, or 3-CO2H) have been investigated by the stopped-flow technique.Simple first-order dependence on MnIII complex and reductant concentrations has been observed for hydrazine, which shows a rate with +>-1 dependence.For hydroxylamine, complex kinetic dependences on reductant and hydrogen-ion concentration suggest a composite inner-sphere mechanism.Also, in the case of the diols an inner-sphere mechanism, through intermediate association, is proposed; for these substrates experimental rates, higher than those computed with the Marcus cross relation, and limiting kinetics are in agreement with the lability of the oxidizing complex.
- Arselli, Patrizia,Mentasti, Edoardo
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p. 689 - 696
(2007/10/02)
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