Journal ArticleDOI
Theoretical study of the catalytic mechanism of catechol oxidase
Mireia Güell,Per E. M. Siegbahn +1 more
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The mechanism for the oxidation ofcatechol by catechol oxidase has been studied using B3LYP hybrid density functional theory and the quantitative potential energy profile of the reaction is discussed in connection with experimental data.Abstract:
The mechanism for the oxidation of catechol by catechol oxidase has been studied using B3LYP hybrid density functional theory. On the basis of the X-ray structure of the enzyme, the molecular system investigated includes the first-shell protein ligands of the two metal centers as well as the second-shell ligand Cys92. The cycle starts out with the oxidized, open-shell singlet complex with oxidation states Cu2(II,II) with a μ-η2:η2 bridging peroxide, as suggested experimentally, which is obtained from the oxidation of Cu2(I,I) by dioxygen. The substrate of each half-reaction is a catechol molecule approaching the dicopper complex: the first half-reaction involves Cu(I) oxidation by peroxide and the second one Cu(II) reduction. The quantitative potential energy profile of the reaction is discussed in connection with experimental data. Since no protons leave or enter the active site during the catalytic cycle, no external base is required. Unlike the previous density functional theory study, the dicopper complex has a charge of +2.read more
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Quantum chemical studies of mechanisms for metalloenzymes.
TL;DR: The most often encountered reaction of the Fe(III)−O2 species is an electrophilic attack on an electron-rich (co)substrate that yields an Fe(II) intermediate with a peroxide bridge between the ferrous ion and an organic molecule (Figure 57).
Journal ArticleDOI
The quantum chemical cluster approach for modeling enzyme reactions
Per E. M. Siegbahn,Fahmi Himo +1 more
TL;DR: In this paper, the general concepts behind the quantum chemical clusterapproach formodeling enzyme active sites and reaction mechanisms are described, as well as the underlying density functional electronic circuits.
Journal ArticleDOI
Bimetallic catalysis involving dipalladium(I) and diruthenium(I) complexes.
TL;DR: The mechanism for aldehyde olefination with ethyl diazoacetate and PPh(3), catalyzed by 2, has been fully elucidated and it is demonstrated that 2 catalyzes the formation of phosphorane utilizing EDA and P Ph, which subsequently reacts with alde Hyde to produce a new olefin and phosphine oxide.
Journal ArticleDOI
Small-molecule models of tyrosinase: From ligand hydroxylation to catalytic monooxygenation of external substrates
TL;DR: The influence of the ligand framework on the catalytic conversion of external substrates is investigated and new dicopper complexes exhibiting ligand hydroxylation reactions are investigated, with implications on the mechanism of tyrosinase and catechol oxidase.
Journal ArticleDOI
The synthesis, characterization and catecholase activity of dinuclear cobalt(II/III) complexes of an O-donor rich Schiff base ligand
Suman Kr Dey,Arindam Mukherjee +1 more
TL;DR: In this paper, three dinuclear CoIII/II complexes (CoIII2(H2L)2(OAc)2) with two CoIII centers were synthesized and characterized using single crystal X-ray diffraction and other analytical methods.
References
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Density‐functional thermochemistry. III. The role of exact exchange
TL;DR: In this article, a semi-empirical exchange correlation functional with local spin density, gradient, and exact exchange terms was proposed. But this functional performed significantly better than previous functionals with gradient corrections only, and fits experimental atomization energies with an impressively small average absolute deviation of 2.4 kcal/mol.
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Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density
TL;DR: Numerical calculations on a number of atoms, positive ions, and molecules, of both open- and closed-shell type, show that density-functional formulas for the correlation energy and correlation potential give correlation energies within a few percent.
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Density-functional exchange-energy approximation with correct asymptotic behavior.
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Journal ArticleDOI
A New Mixing of Hartree-Fock and Local Density-Functional Theories
TL;DR: In this article, a new coupling of Hartree-Fock theory with local density functional theory was proposed to improve the predictive power of the Hartree−Fock model for molecular bonding, and the results of tests on atomization energies, ionization potentials, and proton affinities were reported.
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Ab initio effective core potentials for molecular calculations. Potentials for K to Au including the outermost core orbitals
P. Jeffrey Hay,Willard R. Wadt +1 more
TL;DR: In this article, effective core potentials (ECP) have been derived to replace the innermost core electron for third row (K), fourth row (Rb-Ag), and fifth row (Cs-Au) atoms.