Search results for "reduction"
showing 10 items of 2058 documents
Intramolecular electron transfer between molybdenum and iron mimicking bacterial sulphite dehydrogenase
2014
Diferrocenyl/diferrocenium substituted dioxido molybdenum(VI) complexes [Fe2MoO2] 2(Fc)/[2(FC)]²⁺ mimic the catalytic active site including the redox subunits as well as the catalytic function of bacterial sulphite oxidases.
Reduced Apo-Fumarate Nitrate Reductase Regulator (ApoFNR) as the Major Form of FNR in Aerobically Growing Escherichia coli▿
2008
ABSTRACT Under anoxic conditions, the Escherichia coli oxygen sensor FNR (fumarate nitrate reductase regulator) is in the active state and contains a [4Fe-4S] cluster. Oxygen converts [4Fe-4S]FNR to inactive [2Fe-2S]FNR. After prolonged exposure to air in vitro, apoFNR lacking a Fe-S cluster is formed. ApoFNR can be differentiated from Fe-S-containing forms by the accessibility of the five Cys thiol residues, four of which serve as ligands for the Fe-S cluster. The presence of apoFNR in aerobically and anaerobically grown E. coli was analyzed in situ using thiol reagents. In anaerobically and aerobically grown cells, the membrane-permeable monobromobimane labeled one to two and four Cys res…
O2 as the regulatory signal for FNR-dependent gene regulation in Escherichia coli
1996
With an oxystat, changes in the pattern of expression of FNR-dependent genes from Escherichia coli were studied as a function of the O2 tension (pO2) in the medium. Expression of all four tested genes was decreased by increasing O2. However, the pO2 values that gave rise to half-maximal repression (pO(0.5)) were dependent on the particular promoter and varied between 1 and 5 millibars (1 bar = 10(5) Pa). The pO(0.5) value for the ArcA-regulated succinate dehydrogenase genes was in the same range (pO(0.5) = 4.6 millibars). At these pO2 values, the cytoplasm can be calculated to be well supplied with O2 by diffusion. Therefore, intracellular O2 could provide the signal to FNR, suggesting that…
The oxidation of ubiquinol by the isolated rieske iron-sulfur protein in solution
1990
The pre-steady-state redox reactions of the Rieske iron-sulfur protein isolated from beef heart mitochondria have been characterized. The rates of oxidation by c-type cytochromes is much faster than the rate of reduction by ubiquinols. This enables the monitoring of the oxidation of ubiquinols by the Rieske protein through the steady-state electron transfer to cytochrome c in solution. The pH and ionic strength dependence of this reaction indicate that the ubiquinol anion is the direct reductant of the oxidized cluster of the iron-sulfur protein. The second electron from ubiquinol is diverted to oxygen by the isolated Rieske protein, and forms oxygen radicals that contribute to the steady-s…
Redox tuning and species distribution in Maya Blue-type materials: a reassessment.
2013
Maya Blue-type specimens prepared from indigo (1 wt %) plus kaolinite, montmorillonite, palygorskite, sepiolite, and silicalite are studied. Liquid chromatography with diode array detection, ultra-performance liquid chromatography coupled with mass spectrometry, and pyrolysis-silylation gas chromatography-mass spectrometry analyses of the extracts from these specimens combined with spectral and solid-state voltammetry, electrochemical impedance spectroscopy, and scanning electrochemical microscopy techniques provide evidence for the presence of a significant amount of dehydroindigo and isatin accompanying indigo and other minority organic compounds in all samples. Solid-state electrochemist…
Vectofocimetry: Dioptric power measurement in manual focimeters using power vectors
2021
Abstract Dioptric power measurement is classically achieved using manual focimeters. In this contribution, we present vectofocimetry as a novel methodology to be easily implemented in manual focimeters for improving their capabilities regarding dioptric power measurement. The new procedure is conceptually based on power vector formalism of dioptric power which represents the dioptric power as three values in the form of [M, J0, J45], it uses an iterative process of blur reduction, and it only requires a few modifications in the device that are easy-to-adapt and cost-effective. As a result, dioptric power measurements are easily and quickly obtained with comparable results to the reported on…
Privātskološana un vecāku satraukums par izglītību Ķīnas "dubultās samazināšanas" politikas kontekstā
2022
Privātskološanas izplatība politikas veidotājiem rada grūtības. Ķīnas “Dubultās samazināšanas” politika paredz samazināt privātskološanu, lai atvieglotu slodzi skolēniem. Šī darba mērķis ir atrast galvenos cēloņus, kāpēc vecākiem ir trauksme par savu bērnu izglītību, meklējot saistību starp privātskološanu un vecāku satraukumu par bērnu izglītību. Pētījums ir balstīts uz literatūras izpēti un anketu, kurā piedalījās 656 vecāki, kuru bērni ir 1. līdz 12. klases skolēni Ķīnā. Rezultāti liecina, ka vecākiem jau bija raksturīga konkurences psiholoģija, un vecāku trauksme par bērnu izglītību vairāk veicina privātskološanas uzplaukumu, nevis privātskološana rada vecāku trauksmi par bērnu izglītīb…
Éducation et formation a Madagascar :
2002
International audience; The prospects for educational development are excellent in Madagascar, in light of the increasingly favorable, policy environment for the sector. Public spending for education, relative to the gross domestic product declined in the 90s, coinciding with a five-fold rise in the country's interest payment for external debt. As the debt service burden began to ease in the late 90s, public spending on education began to recover, and can be expected to grow. A key challenge however, is to transform the sector's public spending into educational outcomes that would make significant contributions to poverty reduction. The report identifies challenges at all levels of formal e…
Oxidative DNA damage induced by visible light in mammalian cells: extent, inhibition by antioxidants and genotoxic effects
1998
The extent of the indirect DNA damage generated in mammalian cells by visible light because of the presence of endogenous photosensitizers was studied by means of repair endonucleases. In immortalized human keratinocytes (HaCaT cells) exposed to low doses of natural sunlight, the yield of oxidative DNA base modifications sensitive to the repair endonuclease formamidopyrimidine-DNA glycosylase (Fpg protein) generated by this indirect mechanism was 10% of that of pyrimidine dimers (generated by direct DNA excitation). A similar yield of Fpg-sensitive modifications, which include 8-hydroxyguanine, was observed in primary keratinocytes. The relative yield of oxidative base modifications decreas…
Fast Approximated Discriminative Common Vectors Using Rank-One SVD Updates
2013
An efficient incremental approach to the discriminative common vector (DCV) method for dimensionality reduction and classification is presented. The proposal consists of a rank-one update along with an adaptive restriction on the rank of the null space which leads to an approximate but convenient solution. The algorithm can be implemented very efficiently in terms of matrix operations and space complexity, which enables its use in large-scale dynamic application domains. Deep comparative experimentation using publicly available high dimensional image datasets has been carried out in order to properly assess the proposed algorithm against several recent incremental formulations.