Correction: Morales et al. Characterizing Biogenic MnOx Produced by MnB1 and Its Catalytic Activity towards Water Oxidation. 2024, , 171.

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Characterizing Biogenic MnOx Produced by MnB1 and Its Catalytic Activity towards Water Oxidation.

Mn-oxidizing microorganisms oxidize environmental Mn(II), producing Mn(IV) oxides. MnB1 is a widely studied organism for the oxidation of manganese(II) to manganese(IV) by a multi-copper oxidase. The biogenic manganese oxides (BMOs) produced by MnB1 and similar organisms have unique properties compared to non-biological manganese oxides.

Buffer Effects in Zirconium-Based UiO Metal-Organic Frameworks (MOFs) That Influence Enzyme Immobilization and Catalytic Activity in Enzyme/MOF Biocatalysts.

Novel biocatalysts that feature enzymes immobilized onto solid supports have recently become a major research focus in an effort to create more sustainable and greener chemistries in catalysis. Many of these novel biocatalyst systems feature enzymes immobilized onto metal-organic frameworks (MOFs), which have been shown to increase enzyme activity, stability, and recyclability in industrial processes. While the strategies used for immobilizing enzymes onto MOFs can vary, the conditions always require a buffer to maintain the functionality of the enzymes during immobilization.

Preparation and Properties of an MnHydroxide Complex: Proton and Electron Transfer at a Mononuclear Manganese Site and its Relationship to the Oxygen Evolving Complex within Photosystem II.

Photosynthetic water oxidation is catalyzed by a MnOCa cluster with an unprecedented arrangement of metal ions in which a single manganese center is bonded to a distorted MnOCa cubane-like structure. Several mechanistic proposals describe the unique manganese center as a site for water binding and subsequent formation of a high valent Mn-oxo center that reacts with a M-OH unit (M = Mn or Ca) to form the O-O bond. The conversion of low valent Mn-OH (n = 1,2) to a Mn-oxo species requires that a single manganese site be able to accommodate several oxidation states as the water ligand is deprotonated.

Formation, structure, and EPR detection of a high spin Fe(IV)-oxo species derived from either an Fe(III)-oxo or Fe(III)-OH complex.

High spin oxoiron(IV) complexes have been proposed to be a key intermediate in numerous nonheme metalloenzymes. The successful detection of similar complexes has been reported for only two synthetic systems. A new synthetic high spin oxoiron(IV) complex is now reported that can be prepared from a well-characterized oxoiron(III) species.

Lessons from nature: unraveling biological CH bond activation.

The cleavage of unactivated CH bonds is one of the most challenging reactions in chemical biology. Metalloenzymes have evolved that efficiently perform these transformations with exquisite control of selectivity; however, a proposed requirement is the generation of highly reactive intermediates that could be lethal. A thermodynamic argument involving the putative reactive species is outlined, whereby the interplay between two tunable parameters, redox potential and pK(a), may be the key to sustainable function.

Reaction of cytochrome P450BM3 and peroxynitrite yields nitrosyl complex.

Peroxynitrite has come into the spotlight in recent years. Its effects on proteins have been implicated in several diseases such as acute lung injury, rheumatoid arthritis, implant rejection, artherosclerosis, Parkinson's disease, and Alzheimer's disease. Peroxynitrite is thought to inactivate a variety of proteins including thiolate-ligated heme proteins such as cytochrome P450 2B1 and PGI2 synthase, through the nitration of tyrosine residues.

Evidence for basic ferryls in cytochromes P450.

Using a combination of Mössbauer spectroscopy and density functional calculations, we have determined that the ferryl forms of P450(BM3) and P450cam are protonated at physiological pH. Density functional calculations were performed on large active-site models of these enzymes to determine the theoretical Mössbauer parameters for the ferryl and protonated ferryl (Fe(IV)OH) species. These calculations revealed a significant enlargement of the quadrupole splitting parameter upon protonation of the ferryl unit.

Resonance Raman spectroscopy of chloroperoxidase compound II provides direct evidence for the existence of an iron(IV)-hydroxide.

We report direct evidence for the existence of an iron(IV)-hydroxide. Resonance Raman measurements on chloroperoxidase compound II (CPO-II) reveal an isotope ((18)O and (2)H)-sensitive band at nu(Fe-O) = 565 cm(-1). Preparation of CPO-II in H(2)O using H(2)(18)O(2) results in a red-shift of 22 cm(-1), while preparation of CPO-II in (2)H(2)O using H(2)O(2) results in a red-shift of 13 cm(-1).

Evidence for two ferryl species in chloroperoxidase compound II.

Using a combination of density functional calculations and Mössbauer spectroscopy, we have examined chloroperoxidase compound II (CPO-II). The Mössbauer spectrum of CPO-II suggests the presence of two distinct ferryl species in an approximately 70:30 ratio. Density functional calculations and cryogenic reduction and annealing experiments allow us to assign the major species as an Fe(IV)OH intermediate.

X-ray absorption spectroscopy of chloroperoxidase compound I: Insight into the reactive intermediate of P450 chemistry.

We report the structural characterization of a thiolate-ligated ferryl radical. Using x-ray absorption spectroscopy, we examined chloroperoxidase (CPO) compound I (CPO-I). Our results indicate that CPO-I is an authentic ferryl species with an Fe-O bond of 1.