Aggregation of uroporphyrin I and its metal derivatives in aqueous solution: Raman difference spectroscopy and absorption spectroscopy

Shelnutt, John A.; Dobry, M. M.; Satterlee, James D.

doi:10.1021/j150665a038

Cited by 55 publications

(38 citation statements)

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“…60 The kinetics of oxidation of methyl phenyl sulfide by CDNAcMP-11 ( 0 = 3.3 x 10 -7 M s -1 ) yield results similar to those obtained with MP-11 indicating that the CD group does not play a role in the catalytic mechanism. Confirmation of this was obtained from the enantioselectivity data which showed that the sulfoxide 65 product which formed was essentially racemic (Table 3). It is possible that the sulfide does form an inclusion complex with the CD cavity but that the exposed nature of the haem group allows other non-bound sulfide molecules to react with the peroxide generated Compound I species of microperoxidase.…”

Section: Kinetics Of Sulphide Oxidationmentioning

confidence: 53%

“…The volumes of ethylene glycol and glycerol were measured gravimetrically due to the viscosity of the solvents. In cases where 65 high organic solvent concentrations caused buffer precipitation, the precipitate was removed by centrifugation prior to spectroscopic measurement. The extinction coefficients of the sulfide and sulfoxide compounds were measured in the each solvent mixture and used in the calculations.…”

Section: Equationmentioning

confidence: 99%

“…mM MgSO 4 using a 3 mm diameter glassy carbon (GC) electrode 65 (CH-Instruments). The electrode was rinsed with methanol and water before polishing with a 0.05 m -alumina slurry (CHInstruments).…”

Section: Electrochemical Measurementsmentioning

confidence: 99%

“…The effect of ionic strength on the initial rate of sulfoxidation of 65 methyl phenyl sulfide was investigated. Increased levels of dimerisation of metalloporphyrins have been reported at higher ionic strength due to shielding of the anionic charges on the monomers which can cause electrostatic repulsion 65 .…”

Section: Increase In  0 At Low Alcohol Concentrationsmentioning

confidence: 99%

“…Increased levels of dimerisation of metalloporphyrins have been reported at higher ionic strength due to shielding of the anionic charges on the monomers which can cause electrostatic repulsion 65 . A similar trend was observed for NAcMP-8 44 .…”

Section: Increase In  0 At Low Alcohol Concentrationsmentioning

confidence: 99%

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The effect of solvent on the catalytic properties of microperoxidase-11

O’Reilly

Magner

2011

Phys. Chem. Chem. Phys.

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The effect of a range of solvents on the catalytic oxidation of methyl phenyl sulfide to methyl phenyl sulfoxide by MP-11 and by a cyclodextrin derivative of MP-11 was examined. The addition of low concentrations of alcohols enhanced the initial rate of sulfoxidation rate, most likely due to dispersion of MP-11 aggregates. Higher alcohol concentrations resulted in a decrease in activity arising from solvation of the hydrophobic sulfide, disrupting binding to the catalyst. In alcohols 10 the yield of product was decreased arising from increased rates of MP-11 deactivation via the formation of aldehydes (for primary alcohols) or by peroxide deactivation. The catalytic activity of cyclodextrin modified MP-11 was similar to that of MP-11 itself, demonstrating that it is the Ntermianal side of MP-11 which is the determinant of catalytic activity. Introduction 15The function of enzymes and proteins in non-aqueous solvents has been well established and, in some cases, commercialised [1][2][3][4][5] . Enzyme catalysis and biosensing in organic solvents offers many advantages over aqueous-based processes including increased substrate/analyte solubility, enhanced thermal stability, more 20 favourable reaction thermodynamics, ease of product / biocatalyst recovery and modified selectivity 1,2,[6][7][8][9][10] . The peroxidases are an important group of enzymes which catalyse a wide variety of synthetically useful oxidation reactions using peroxides as oxidants. In spite of this, their potential in non-aqueous catalytic 25 systems has yet to be realised. This may, in part, be attributed to deactivation of the enzymes by the peroxide oxidant at the concentrations required for such reactions [10][11][12] . Strategies to overcome this problem have been developed, including the slow addition 13 or in-situ generation 14 of the peroxide. Alternatively, 30 studies have shown that a high concentration of substrate relative to the peroxide aids the regeneration of the native enzyme and prevents the formation of the peroxidase intermediates which result in enzyme deactivation [15][16][17] . Microperoxidases (MPs) are the products of the proteolytic 35 digestion of cytochrome c. MP-11 contains residues 11 -21 of the parent protein and is prepared by the action of pepsin on cytochrome c. The haem group is covalently attached to the Cys14 and Cys17 residues via sulfide bonds and is coordinated on the proximal side by the imidazole nitrogen of His18. The 6th axial 40 ligand position is either unoccupied or loosely coordinated by water 18 . In this respect the haem configuration is analogous to that of the peroxidase enzymes and MP-11 displays typical peroxidase activity.The array of reactions catalysed by MPs is extensive. The 45 oxidation of phenolic substrates 17,19,20 , peroxide decomposition 21 , sulfide oxidation 22 , Mn 2+ oxidation 23 , the nitration of phenol in the presence of NO 2 -24 , the oxidation of N-methylcarbazole 25 and the dehalogenation of halophenols 26 have all been reported. Thus MPs display activity similar not on...

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Section: Kinetics Of Sulphide Oxidationmentioning

confidence: 53%

Section: Equationmentioning

confidence: 99%

Section: Electrochemical Measurementsmentioning

confidence: 99%

Section: Increase In  0 At Low Alcohol Concentrationsmentioning

confidence: 99%

Section: Increase In  0 At Low Alcohol Concentrationsmentioning

confidence: 99%

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The effect of solvent on the catalytic properties of microperoxidase-11

O’Reilly

Magner

2011

Phys. Chem. Chem. Phys.

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Medium effects on the dimerization of coproporphyrin-I free base

Morales‐Rojas

Yatsimirsky

1999

J. Phys. Org. Chem.

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Kinetics of the Metallation of Coproporphyrin-I in Water with Cadmium(II) and Manganese(II)

Bartocci

Giovannetti

Carsetti

1998

J. Porphyrins Phthalocyanines

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The reaction of 3,8,13,18-tetramethyl-21H,23H-porphine-2,7,12,17-tetrapropionic acid or coproporphyrin-I ( CPI ) with cadmium(II) was studied spectrophotometrically and its kinetic and equilibrium constants were determined. The influence of temperature on the reaction rate was also studied. At different ratios of [ CPI ]/[ Cd(II) ] two types of complex were formed: CdII ( CPI ) and ( CdII )2( CPI ); an investigation of the solution properties and the mechanism of aggregation of ( CdII )2( CPI ) at different pH were performed. It is verified that cadmium(II) accelerates the reaction of the incorporation of manganese(II) into CPI by the substitution of cadmium(II) with manganese(II) in the CdII ( CPI ) complex; the kinetics and mechanism of this substitution reaction at alkaline pH were studied. A sensitive kinetic method for the determination of cadmium(II) at ppb levels has been established; the molar absorptivity and the Sandell's sensitivity (for A = 0.001) of the recommended procedure at 458 nm and 300 s after the start of the reaction are (6.175 ± 0.026) × 105 1 mol−1 cm−1 and (1.820 ± 0.008) × 10−4 μg cm−2 respectively.

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Aggregation of uroporphyrin I and its metal derivatives in aqueous solution: Raman difference spectroscopy and absorption spectroscopy

Cited by 55 publications

References 0 publications

The effect of solvent on the catalytic properties of microperoxidase-11

The effect of solvent on the catalytic properties of microperoxidase-11

Medium effects on the dimerization of coproporphyrin-I free base

Kinetics of the Metallation of Coproporphyrin-I in Water with Cadmium(II) and Manganese(II)

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