Cytochrome P450 monooxygenase and superoxide reductase (SOR) have the same first atom coordination shell at their iron active sites: an Fe[N(4)S] center in a square-pyramidal geometry with the sixth coordinate site open for the catalytic reaction. Furthermore, both pass through ferric hydroperoxo intermediates. Despite these similarities, the next step in their catalytic cycle is very different: distal oxygen protonation and O-O cleavage (P450) versus proximal oxygen protonation and H(2)O(2) release (SOR). One of the factors leading to this difference is the spin state of the intermediates. Density functional theory (DFT) applied to models for the ferric hydroperoxo, (SCH(3))(L)Fe(III)-OOH (L = porphyrin for P450 and four imidazoles for SOR), gives different ground spin states; the P450 model with the porphyrin, which contrains the Fe-N distances, prefers a low-spin ground state, whereas the SOR model with four histidines, in which Fe-N bonds are extendable, prefers a high-spin ground state. Their ground spin states lead to geometric and electronic structures that assist in (1) the protonation on distal oxygen for P450, which leads to O-O bond cleavage and formation of the oxo-ferryl, (SCH(3))(L)Fe(IV) horizontal lineO (Cpd I), and H(2)O, and (2) the protonation on proximal oxygen for SOR, which leads to the formation of the ferric hydrogen peroxide, (SCH(3))(L)Fe(III)-HOOH, intermediate before the Fe-O bond cleavage and H(2)O(2) production. Specifically, the quartet ground state of the water-bound oxo-ferryl, (SCH(3))(L)Fe(IV) horizontal lineO...H(2)O, is more stable than the sextet ground state of (SCH(3))(L)Fe(III)-HOOH by -14.29 kcal/mol for the P450 model. Another important factor is the differences in the location of the active site: P450's active site is embedded within the enzyme, whereas SOR's active site is exposed to the aqueous environment. In the latter location, water molecules can freely form hydrogen bonds with both proximal and distal oxygen to stabilize the (SCH(3))(L)Fe(III)-HOOH intermediate. When two explicit water molecules are included in the model, the sextet ground state of (SCH(3))(L)Fe(III)-HOOH...2H(2)O is more stable than the quartet ground state of (SCH(3))(L)Fe(IV) horizontal lineO...3H(2)O by -2.14 kcal/mol for the SOR model. Our calculations show that both the spin state, which is controlled by the differences between four N donors in porphyrin versus those in imidazoles, and the degree of solvent exposure of the active sites play important roles in the fate of the (SCH(3))(L)Fe(III)-OOH intermediate, leading to O-O cleavage in one situation (P450) and hydrogen peroxide production in the other (SOR).
Download full-text PDF |
Source |
---|---|
http://dx.doi.org/10.1021/ic9017272 | DOI Listing |
Front Microbiol
December 2024
Department of Earth Sciences, University of Southern California, Los Angeles, CA, United States.
Microbial activity in the deep continental subsurface is difficult to measure due to low cell densities, low energy fluxes, cryptic elemental cycles and enigmatic metabolisms. Nonetheless, direct access to rare sample sites and sensitive laboratory measurements can be used to better understand the variables that govern microbial life underground. In this study, we sampled fluids from six boreholes at depths ranging from 244 m to 1,478 m below ground at the Sanford Underground Research Facility (SURF), a former goldmine in South Dakota, United States.
View Article and Find Full Text PDFBMC Health Serv Res
January 2025
Reform Office, Strategy, Policy and Reform Division, Queensland Health, Floor 13, 33 Charlotte Street, Brisbane, QLD, 4000, Australia.
Background: Commissioning for health services has been implemented as one approach to improve the quality and access to healthcare for First Nations, regional and remote populations. This review systematically scoped the literature for studies that described or evaluated the governance, funding, implementation and outcomes from health service commissioning targeting these groups in Canada, Australia, Aotearoa/New Zealand and the United States (CANZUS nations).
Methods: Seventeen databases were searched for relevant peer reviewed and grey literature studies published in English from 2010 to 2023.
Environ Sci Pollut Res Int
January 2025
Department of Physics, Faculty of Science, King Abdulaziz University, 21589, Jeddah, Saudi Arabia.
A sustainable biosorbent, silver nanoparticles-decorated coffee-ground waste (CWAg), was synthesized through a simple in-situ reduction method. CWAg is extensively characterized via SEM-EDX, PZC, FTIR, XRD, HR-TEM, and XPS analyses. The biosorbent was tested to remove chromium (Cr(VI)) and methylene blue (MB) from wastewater, and its antibacterial properties was evaluated.
View Article and Find Full Text PDFNat Commun
January 2025
Antivortices have potential applications in future nano-functional devices, yet the formation of isolated antivortices traditionally requires nanoscale dimensions and near-zero magnetocrystalline anisotropy, limiting their broader application. Here, we propose an approach to forming antivortices in multiferroic ε-FeO with the coalescence of misaligned grains. By leveraging misaligned crystal domains, the large magnetocrystalline anisotropy energy is counterbalanced, thereby stabilizing the ground state of the antivortex.
View Article and Find Full Text PDFJ Am Chem Soc
January 2025
Department of Chemistry and the Manitoba Institute for Materials, University of Manitoba, 144 Dysart Road, Winnipeg, Manitoba R3T 2N2, Canada.
The ability to manipulate excited-state decay cascades using molecular structure is essential to the application of abundant-metal photosensitizers and chromophores. Ligand design has yielded some spectacular results elongating charge-transfer excited state lifetimes of Fe(II) coordination complexes, but triplet metal-centered (MC) excited states─recently demonstrated to be critical to the photoactivity of isoelectronic Co(III) polypyridyls─have to date remained elusive, with temporally isolable examples limited to the picosecond regime. With this report, we show how strong-field donors and intramolecular π-stacking can conspire to stabilize a long-lived MC excited state for a remarkable 4.
View Article and Find Full Text PDFEnter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!