A fundamental understanding of anomalous redox mechanisms in hexacyanometallate compounds, compared with conventional NaMO2 systems (M: transition metals), is presented based on first-principles calculations and experimental validations. From theoretical calculations, we identified low-spin and high-spin states of Fe ions coordinated by the cyanide group (-CN) with the same oxidation state (Fe2...

BACKGROUND Ring-hydroxylating dioxygenases are multicomponent systems that initiate biodegradation of aromatic compounds. Many dioxygenase systems include Rieske-type ferredoxins with amino acid sequences and redox properties remarkably different from the Rieske proteins of proton-translocating respiratory and photosynthetic complexes. In the latter, the [Fe2S2] clusters lie near the protein su...

The Corg:P ratios of organic-rich facies (TOCN1%) exhibit considerable variation through the Phanerozoic, from b10:1 in the Permian Phosphoria Formation to N1000:1 in some Devonian black shales. Relative to the composition of phytoplankton (C:P ∼106:1), which provide the bulk of organic C and P to organic-rich marine sediments, the range of Phanerozoic sedimentary Corg:P ratios largely reflects...

By mutating the target residue of covalent flavinylation in vanillyl-alcohol oxidase, the functional role of the histidyl-FAD bond was studied. Three His(422) mutants (H422A, H422T, and H422C) were purified, which all contained tightly but noncovalently bound FAD. Steady state kinetics revealed that the mutants have retained enzyme activity, although the turnover rates have decreased by 1 order...

A series of tetranuclear oxo/hydroxo clusters comprised of three Fe centers and a redox-inactive metal (M) of various charge is reported. Crystallographic studies show an unprecedented Fe3M(μ4-O)(μ2-OH) core that remains intact upon changing M or the oxidation state of iron. Electrochemical studies reveal that the reduction potentials (E1/2) span a window of 500 mV and depend upon the Lewis aci...

8 ABSTRACT: The thermodynamic and structural factors that influence the redox properties of 9 an extensive set of tungsten−alkylidyne complexes W(CR)L4X are analyzed by combining 10 synthesis, electrochemistry, and computational modeling based on free energy calculations of 11 oxidation potentials at the density functional theory level. The observed linear correlations 12 among oxidation potent...

The role of pyridinium cations in electrochemistry has been believed known for decades, and their radical forms have been proposed as key intermediates in modern photoelectrocatalytic CO(2) reduction processes. Using first-principles density functional theory and continuum solvation models, we have calculated acidity constants for pyridinium cations and their corresponding pyridinyl radicals, a...

The electrochemical grafting process of 4-nitrobenzene and 4-methoxybenzene (anisole) from diazonium salt solutions has been investigated in situ by monitoring the current density, the band bending, and the nonradiative surface recombination during grafting at different potentials and different concentrations of the diazonium salt in the solution. Ex situ infrared spectroscopic ellipsometry has...

The trinuclear complexes [{(R2bipy)2Ru}3(mu3-HHTP)](PF6)3 [1(PF6)3, R = H; 2(PF6)3, R = 4-tBu] contain three {Ru(R2bipy)2}2+ fragments connected to the triangular tris-chelating ligand hexahydroxytriphenylene (H6HHTP). This bridging ligand contains three dioxolene-type binding sites, each of which can reversibly convert between dianionic catecholate (cat), monoanionic semiquinone (sq) or neutra...

A module for fast determination of reduction potentials, E°, of redox-active proteins has been implemented in the CHARMM INterface and Graphics (CHARMMing) web portal (www.charmming.org). The free energy of reduction, which is proportional to E°, is composed of an intrinsic contribution due to the redox site and an environmental contribution due to the protein and solvent. Here, the intrinsic c...