Terminal molecular oxygen

No clear picture of the primary radical intermediate(s) in the HO2 photooxidation of water has appeared. The nature of the observed radical species depends on the origin and pretreatment of the HO2 sample, on the conditions and extent of its reduction, on the extent of surface hydroxylation, and on the presence of adventitious electron acceptors such as molecular oxygen (41). The hole is trapped on the terminal OH group (54). 

As we have seen, the metabolic energy from oxidation of food materials—sugars, fats, and amino acids—is funneled into formation of reduced coenzymes (NADH) and reduced flavoproteins ([FADHg]). The electron transport chain reoxidizes the coenzymes, and channels the free energy obtained from these reactions into the synthesis of ATP. This reoxidation process involves the removal of both protons and electrons from the coenzymes. Electrons move from NADH and [FADHg] to molecular oxygen, Og, which is the terminal acceptor of electrons in the chain. The reoxidation of NADH,... 

Mechanism and sulphur oxidation Apart from its intrinsic interest the economic importance of acid corrosion and more lately interest in ore leaching, has stimulated considerable work on the oxidation of sulphur, Fe and Mn. It must be stressed that the Thiobacilli are obligate aerobes, i.e. that depend on molecular oxygen as a terminal electron acceptor. Possible reactions for the oxidation of sulphur are... 

There are several available terminal oxidants for the transition metal-catalyzed epoxidation of olefins (Table 6.1). Typical oxidants compatible with most metal-based epoxidation systems are various alkyl hydroperoxides, hypochlorite, or iodo-sylbenzene. A problem associated with these oxidants is their low active oxygen content (Table 6.1), while there are further drawbacks with these oxidants from the point of view of the nature of the waste produced. Thus, from an environmental and economical perspective, molecular oxygen should be the preferred oxidant, because of its high active oxygen content and since no waste (or only water) is formed as a byproduct. One of the major limitations of the use of molecular oxygen as terminal oxidant for the formation of epoxides, however, is the poor product selectivity obtained in these processes [6]. Aerobic oxidations are often difficult to control and can sometimes result in combustion or in substrate overoxidation. In... 

Fig. 3-4 Electron transport process schematic, showing coupled series of oxidation-reduction reactions that terminate with the reduction of molecular oxygen to water. The three molecules of ATP shown are generated by an enzyme called ATPase which is located in the cell membrane and forms ATP from a proton gradient created across the membrane.

We saw previously that a major factor in inhibiting the bimolecular termination reaction was the presence of sufficiently bulky ligands so that a monomeric dioxygen adduct could be isolated 135). A number of synthetic metal porphyrins 239) have been prepared recently which satisfy the above requirement, and bind molecular oxygen we shall now proceed to discuss these. 

Bacteria can grow in two main environments, aerobic and anaerobic. In aerobic treatment, aerobic and facultative bacteria use molecular oxygen as their terminal electron acceptor. The treatment occurs in the presence of a molecular oxygen supply. In anaerobic treatment, anaerobic and... 

More than 90% of commercially available enzyme-based biosensors and analytical kits contain oxidases as terminal enzymes responsible for generation of analytical signal. These enzymes catalyze oxidation of specific analyte with molecular oxygen producing hydrogen peroxide according to the reaction ... 

Cytochrome c and ubiquinol oxidases are part of an enzyme superfamily coupling oxidation of ferrocytochrome c (in eukaryotes) and ubiquinol (in prokaryotes) to the 4 e /4 reduction of molecular oxygen to H2O. After this introduction, we will concentrate on the cytochrome c oxidase enzyme. The two enzymes, cytochrome c oxidase (CcO) and ubiquinol oxidase, are usually defined by two criteria (1) The largest protein subunit (subunit I) possesses a high degree of primary sequence similarity across many species (2) members possess a unique bimetallic center composed of a high-spin Fe(II)/(III) heme in close proximity to a copper ion. Cytochrome c oxidase (CcO) is the terminal... 

This section will cover aspects of monohydride terminal surface reactions that were carried out under free-radical conditions. The description will be circumscribed to the reactions with molecular oxygen and monounsaturated compounds. Mechanistic information for these reactions is scarce mainly due to the complexity of the system, and mechanistic schemes are often proposed in analogy with radical chemistry of organosilane molecules. H—Si(lll) has a band gap of about 1.1 eV while the HOMO LUMO gap in (Me3Si)3SiH is within 8-11 eV and, therefore, has very important consequences for the reactions with nucleophilic and electrophilic species where frontier orbital inter-... 

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