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Superoxide reductase is a nonheme iron metalloenzyme that detoxifies superoxide anion radicals O(2)(•-) in some microorganisms. Its catalytic mechanism was previously proposed to involve a single ferric iron (hydro)peroxo intermediate, which is protonated to form the reaction product H(2)O(2). Here, we show by pulse radiolysis that the mutation of the well-conserved lysine 48 into isoleucine in the SOR from Desulfoarculus baarsii dramatically affects its reaction with O(2)(•-). Although the first reaction intermediate and its decay are not affected by the mutation, H(2)O(2) is no longer the reaction product. In addition, in contrast to the wild-type SOR, the lysine mutant catalyzes a two-electron oxidation of an olefin into epoxide in the presence of H(2)O(2), suggesting the formation of iron-oxo intermediate species in this mutant. In agreement with the recent X-ray structures of the peroxide intermediates trapped in a SOR crystal, these data support the involvement of lysine 48 in the specific protonation of the proximal oxygen of the peroxide intermediate to generate H(2)O(2), thus avoiding formation of iron-oxo species, as is observed in cytochrome P450. In addition, we proposed that the first reaction intermediate observed by pulse radiolysis is a ferrous-iron superoxo species, in agreement with TD-DFT calculations of the absorption spectrum of this intermediate. A new reaction scheme for the catalytical mechanism of SOR with O(2)(•-) is presented in which ferrous iron-superoxo and ferric hydroperoxide species are reaction intermediates, and the lysine 48 plays a key role in the control of the evolution of iron peroxide intermediate to form H(2)O(2).
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http://dx.doi.org/10.1021/ja209297n | DOI Listing |
Adv Sci (Weinh)
December 2024
Soochow Institute for Energy and Materials InnovationS (SIEMIS), Soochow University, Suzhou, 215006, China.
Hydrogen peroxide (HO) is an important chemical in synthetic chemistry with huge demands. Photocatalytic synthesis of HO via oxygen reduction and water oxidation reactions (ORR and WOR) is considered as a promising and desirable solution for on-site applications. However, the efficiency of such a process is low due to the poor solubility of molecular oxygen and the rapid reverse reaction of hydroxyl radicals (OH) with hydrogen atoms (H).
View Article and Find Full Text PDFSci Bull (Beijing)
December 2024
School of Chemistry and Chemical Engineering/Institute of Clean Energy and Materials/Guangzhou Key Laboratory for Clean Energy and Materials/Huangpu Hydrogen Innovation Center, Guangzhou University, Guangzhou 510006, China. Electronic address:
Photocatalytic hydrogen peroxide (HO) generation is largely subject to the sluggish conversion kinetics of the superoxide radical (O) intermediate, which has relatively low reactivity and requires high energy. Here, we present a lattice-strain strategy to accelerate the conversion of O to highly active singlet oxygen(O) by optimizing the distance between two adjacent active sites, thereby stimulating HO generation via low-barrier oxygen-oxygen coupling. As the initial demonstration, the defect-induced strain in ZnInS nanosheet optimizes the distance of two adjacent Zn sites from 3.
View Article and Find Full Text PDFPol Merkur Lekarski
December 2024
I. HORBACHEVSKY TERNOPIL NATIONAL MEDICAL UNIVERSITY, TERNOPIL, UKRAINE.
Objective: . Aim: To investigate changes in oxidative stress indicators in rats under conditions of long-term ethanol exposure.
Patients And Methods: Materials and Methods: We studied the effect of prolonged exposure to ethanol on the activity of free radical processes in the gonads of rats of both sexes.
Adv Sci (Weinh)
December 2024
Key Laboratory of Materials Physics, Centre for Environmental and Energy Nanomaterials, Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, HFIPS, Chinese Academy of Sciences, Hefei, 230031, China.
Cyclohexanone oxime, a critical precursor for nylon-6 production, is traditionally synthesized via the hydroxylamine method under industrial harsh conditions. Here is present a one-step electrochemical integrated approach for the efficient production of cyclohexanone oxime under ambient conditions. This approach employed the coupling of in situ electro-synthesized HO over a cobalt (Co)-based electrocatalyst with the titanium silicate-1 (TS-1) heterogeneous catalyst to achieve the cyclohexanone ammoximation process.
View Article and Find Full Text PDFJ Med Chem
December 2024
Key Laboratory of Medicinal Chemistry and Molecular Diagnosis of Ministry of Education, Key Laboratory of Pharmaceutical Quality Control of Hebei Province, College of Pharmacy, Hebei University, Baoding 071002, Hebei, P. R. China.
The emerged apoptosis/ferroptosis synergistic platinum-based therapy has attracted a lot of attention but is far from clinic use due to high systemic toxicity. Herein, a series of novel precise carrier-free self-assembled platinum(IV) nanoparticles with lipid regulation effect named FSPNPs (NPs-NPs) were constructed via connecting fenofibrate acid (FA) to cisplatin or oxaliplatin-derived platinum(IV)-intermediates with disulfide bonds. FSPNPs can be stimulated by high-glutathione/ascorbic acid and acidity environment to produce an "explosion-like" cascade release process.
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