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Reactions hydroxylation

Iron Absorption. A very important effect of ascorbic acid is the enhancement of absorption of nonheme iron from foods. Ascorbic acid also enhances the reduction of ferric iron to ferrous iron. This is important both in increasing iron absorption and in its function in many hydroxylation reactions (140,141). In addition, ascorbic acid is involved in iron metaboHsm. It serves to transfer iron to the Hver and to incorporate it into ferritin. [Pg.22]

A large proportion (30-90% in tropical waters) is absorbed by bacteria and oxidized to FfjS in order to allow the sulfur to be used by these organisms. Once in the atmosphere, DMS is oxidized by various free radicals such as hydroxyl and nitrate ions. In the presence of low concentrations of NO the hydroxyl reaction... [Pg.26]

Analogous side-chain oxidations occur in various biosynthetic pathways. The neurotransmitter norepinephrine, for instance, is biosynthesized from dopamine by a benzylic hydroxylation reaction. The process is catalyzed by the copper-containing enzyme dopamine /3-monooxygenase and occurs by a radical mechanism. A copper-oxygen species in the enzyme first abstracts the pro-R benzylic hydrogen to give a radical, and a hydroxyl is then transferred from copper to carbon. [Pg.577]

The hydroxylation reaction, whose stereochemical course is controlled by the strong inherent preference for the formation of a cis-fused 5,5 ring system, creates a molecule which would appear to be well suited for an intramolecular etherification reaction to give ring E of ginkgolide B (1). Indeed, when a solution of 11 in methylene chloride is exposed to camphorsulfonic acid (CSA), a smooth cycli-zation reaction takes place to give intermediate 10 in an overall yield of 75% from 12. The action of CSA on 11 produces a transient oxonium ion at C-12 which is intercepted intramolecularly by the proximal hydroxyl group at C 4. [Pg.461]

Another hydroxylation reaction is the Elbs reaction In this method, phenols can be oxidized to p-diphenols with K2S20g in alkaline solution. Primary, secondary, or tertiary aromatic amines give predominant or exclusive ortho substitution unless both ortho positions are blocked, in which case para substitution is found. The reaction with amines is called the Boyland-Sims oxidation. Yields are low with either phenols or amines, generally under 50%. The mechanisms are not clear, but for the Boyland-Sims oxidation there is evidence that the S20 ion attacks at the ipso position, and then a migration follows. ... [Pg.724]

Martin G, S Dijols, C Capeillere-Blandin, 1 Arnaud (1999) Hydroxylation reaction catalyzed by the Burk-holderia cepacia ACllOO bacterial strain. Involvement of the chlorophenol-4-monooxygenase. Eur J Bioichem 261 533-538. [Pg.444]

Although the structure of the hydroxylase is now reasonably well understood, less is known about the interactions among the three component proteins of MMO. Despite the fact that the physical properties of the M. capsulatus (Bath) and M. trichosporium OB3b hydroxylases are very similar, preliminary work with the other components indicates that significant differences exist. The manner in which the component proteins interact is quite complex, as manifested by the regulation of electron transfer to the hydroxylase, the product yields and regioselec-tivity of the hydroxylation reaction, and the detailed kinetic behavior of the systems. [Pg.272]

In the M. capsulatus (Bath) system, all three components are necessary to obtain turnover with NADH as the reductant (57). With the M. trichosporium OB3b system, protein B is apparently not required (27). Instead, in this latter system, protein B increases the initial rates of the catalytic hydroxylation reaction (27). Catalysis can be achieved by means of a shunt pathway with hydrogen peroxide and Hox alone from both organisms (58-60). The efficiency of the shunt pathway, however, varies significantly. With M. trichosporium OB3b, alcohol yields greater than those obtained with the completely reconstituted system have been observed (58). Furthermore, upon addition of protein... [Pg.272]

Fig. 4. Substrate first binds to the complete system containing all three protein components. Addition of NADH next effects two-electron reduction of the hydroxylase from the oxidized Fe(III)Fe(III) to the fully reduced Fe(II)Fe(II) form, bypassing the inactive Fe(II)Fe(III) state. The fully reduced hydroxylase then reacts with dioxygen in a two-electron step to form the first known intermediate, a diiron(III) peroxo complex. The possibility that this species itself is sufficiently activated to carry out the hydroxylation reaction for some substrates cannot be ruled out. The peroxo intermediate is then converted to Q as shown in Fig. 3. Substrate reacts with Q, and product is released with concomitant formation of the diiron(III) form of the hydroxylase, which enters another cycle in the catalysis. Fig. 4. Substrate first binds to the complete system containing all three protein components. Addition of NADH next effects two-electron reduction of the hydroxylase from the oxidized Fe(III)Fe(III) to the fully reduced Fe(II)Fe(II) form, bypassing the inactive Fe(II)Fe(III) state. The fully reduced hydroxylase then reacts with dioxygen in a two-electron step to form the first known intermediate, a diiron(III) peroxo complex. The possibility that this species itself is sufficiently activated to carry out the hydroxylation reaction for some substrates cannot be ruled out. The peroxo intermediate is then converted to Q as shown in Fig. 3. Substrate reacts with Q, and product is released with concomitant formation of the diiron(III) form of the hydroxylase, which enters another cycle in the catalysis.
Physical studies of the hydroxylase have established the structural nature of the diiron core in its three oxidation states, Hox, Hmv, and Hred. Although the active site structures of hydroxylase from M. tri-chosporium OB3b and M. capsulatus (Bath) are similar, some important differences are observed for other features of the two MMO systems. The interactions with the other components, protein B and reductase, vary substantially. More structural information is necessary to understand how each of the components affects the others with respect to its physical properties and role in the hydroxylation mechanism and to reconcile the different properties seen in the two MMO systems. The kinetic behavior of intermediates in the hydroxylation reaction cycle and the physical parameters of intermediate Q appear similar. The reaction of Q with substrate, however, varies. The participation of radical intermediates is better established with the M. triehosporium... [Pg.288]

Despite some of the melt fabrication problems, the organosiloxane systems produced by the silylamine-hydroxyl reaction ( ) produced interesting, perfectly alternating copolymers. [Pg.186]

Ullrich, V. Cytochrome P450 and Biological Hydroxylation Reactions. 83, 67-104 (1979). [Pg.168]

Compared with isolated enzymes, enzymes used in whole-cell biotransformations are often more stable due to the presence of their natural environment inside the cell. This is especially true for the enzymes involved in the oxidation and hydroxylation reactions that are labile once isolated from the cells. They are a convenient and stable source of enzymes that are often synthesized by cells in response to the presence of the substrate. [Pg.233]

Among the mononuclear non-haem iron enzymes catalysing hydroxylation reactions (Table 2.3) we can distinguish between intramolecular dioxygenases and external mononoxygenases. The former can be divided into those which are pterin-dependent and those which use a-ketoacids such as a-keto glutarate as obligatory... [Pg.83]

Keywords Biological degradation, Cytochrome P450, Hydroxylation reaction, Polybrominated diphenyl ether, Trametes versicolor... [Pg.242]

Regarding the degradation of PBDEs by white-rot fungi, the first evidence of their ability to degrade a PBDE compound corresponds to a study published by Hundt et al. [27], which studied the degradation of 4-bromo-BDE by Trametes versicolor. The degradation occurs initially by hydroxylation reaction with the possible formation of three different isomers of hydroxy-diphenyl ether followed... [Pg.247]

In summary, two general pathways are now accepted as the reaction basis of pyridine degradation by bacteria. One involves (i) hydroxylation reactions, followed by reduction, e.g., on Bacillus strain 4 and the other (ii) (aerobic) reductive pathway(s) not initiated by hydroxylations, e.g., on Nocardia strain Zl [348], Two review articles, one by Kaiser [320] and the other by Fetzner [326] gave the complete microbial metabolic pathways for several nitrogen compounds carried out in the presence of a variety of microorganisms, some of them previously studied by Professor Lingens [349], The complete degradation pathways of pyridine are shown in Fig. 29. [Pg.164]


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2 -deoxyguanosine reaction with hydroxyl radical

A-hydroxylation reactions

Acetaldehyde hydroxyl radical reaction

Acetaldehyde reaction with hydroxyl radicals

Acetylene hydroxyl radical reaction

Acetylene, reaction with hydroxyl radicals

Acrylic acid isocyanate-hydroxyl reactions

Alcohols reaction with hydroxyl radical

Aldehydes hydroxyl radical reaction

Alkanes hydroxyl radical reaction

Alkenes Sharpless asymmetric hydroxylation reactions

Alkenes hydroxyl radical reactions

Alkenes reactions with hydroxyl radical

Alkyl nitrates hydroxyl radical reactions

Amines hydroxyl radical reaction

Ammonia hydroxyl radical reaction

Anilines hydroxylation reactions

Aqueous reactions pyridine hydroxylates

Aromatic amines reactions with hydroxyl radical

Aromatic hydrocarbons hydroxyl radical reactions

Bromination reactions, hydroxyl group conversion

Carbon disulfide hydroxyl radical reaction

Carbon monoxide hydroxyl radical reaction

Carbon monoxide, reaction with hydroxyl radicals

Carbon monoxide, tropospheric reaction with hydroxyl

Carbonates reaction with hydroxyl radical

Carbonyl sulfide hydroxyl radical reaction

Carboxylic acids hydroxyl radical reactions with

Catalysis isocyanate-hydroxyl reactions

Chiral ligands, Sharpless asymmetric hydroxylation reactions

Chlorination reactions, hydroxyl group conversion

Crosslinking reaction, pendant hydroxyl

Crosslinking reaction, pendant hydroxyl group

Diazomethane reaction with hydroxyl

Dimethyl sulfide hydroxyl radical reaction

Dimethyl sulfoxide hydroxyl radical, reaction with

Electrophilic aromatic substitution reactions hydroxylations

Energy of hydroxylation reaction

Epoxide hydroxyl reactions

Ethane reaction with hydroxyl

Ethyl acetate, reaction with hydroxyl ions

Ethylene reaction with hydroxyl

Exchange reactions between hydroxyl protons

Fenton reactions Hydroxylation)

Fluorination reactions, hydroxyl group conversion

Formaldehyde hydroxyl radical reaction

Formaldehyde reaction with hydroxyl radicals

Hydrated electron hydroxyl radical reactions

Hydrazines hydroxyl radical reaction

Hydrogen sulfide, hydroxyl radical reaction

Hydrogen, reaction with hydroxyl

Hydrogen, reaction with hydroxyl radicals

Hydrogen, tropospheric reaction with hydroxyl

Hydroxy group from hydroxylation reaction

Hydroxyl Radical-Mediated 2-Deoxyribose Oxidation Reactions

Hydroxyl addition reactions

Hydroxyl from Fenton reaction

Hydroxyl group reactions amine

Hydroxyl group reactions architecture

Hydroxyl group reactions catalysts

Hydroxyl group reactions ester formation

Hydroxyl group reactions halogens

Hydroxyl group reactions ring-opening polymerization

Hydroxyl group reactions ureas

Hydroxyl group reactions urethanes

Hydroxyl groups reaction with

Hydroxyl groups reactions

Hydroxyl groups removal, deoxygenation reactions

Hydroxyl groups, reaction with benzyl

Hydroxyl ions, from hydrated electron reactions

Hydroxyl radical Fenton reaction

Hydroxyl radical alcohol reactions

Hydroxyl radical amino acid reactions

Hydroxyl radical carboxylic acid reactions

Hydroxyl radical naphthalene, reaction, products

Hydroxyl radical nitric acid reaction

Hydroxyl radical nitric oxide reaction

Hydroxyl radical nitrogen dioxide reaction

Hydroxyl radical production from reaction

Hydroxyl radical reaction rate

Hydroxyl radical reaction rate atmosphere

Hydroxyl radical reaction rates, 245, Table

Hydroxyl radical reaction with

Hydroxyl radical reaction with alkanes

Hydroxyl radical reaction with bromide

Hydroxyl radical reaction with nitric oxide

Hydroxyl radical reaction with nucleic acids

Hydroxyl radical reaction with nucleobases

Hydroxyl radical reactions with aromatic compounds

Hydroxyl radical reactions with nitrogen oxides

Hydroxyl radical sulfur dioxide reaction

Hydroxyl radical with hydrogen peroxide, reaction

Hydroxyl radicals atom reaction with

Hydroxyl radicals chemical reactions

Hydroxyl radicals reaction with gaseous

Hydroxyl radicals reactions with hydrocarbons

Hydroxyl radicals, abstraction reactions

Hydroxyl radicals, reaction with methane

Hydroxyl radicals, reactions

Hydroxyl reaction +EtOH

Hydroxyl reaction types

Hydroxyl reaction with

Hydroxyl reaction with HCHO

Hydroxyl reaction with acetylene

Hydroxyl reaction with alcohols

Hydroxyl reaction with alkane

Hydroxyl reaction with amine

Hydroxyl reaction with carbonate

Hydroxyl reaction with chloride

Hydroxyl reaction with dimethyl formamide

Hydroxyl reaction with elemental carbon

Hydroxyl reaction with ethanol, aqueous

Hydroxyl reaction with formate

Hydroxyl reaction with inorganic anions

Hydroxyl reaction with iodide

Hydroxyl reaction with metal ions

Hydroxyl reaction with nitrite

Hydroxyl reaction with organic molecules

Hydroxyl reaction with sulfate radical

Hydroxyl reaction with sulfite

Hydroxyl reactions, effect

Hydroxyl solution reactions

Hydroxyl, reactions

Hydroxyl, reactions

Hydroxyl-Radical-Induced Reactions

Hydroxyl-Reactive Chemical Reactions

Hydroxyl-directed Diels-Alder reaction

Hydroxylated polyesters reactions

Hydroxylation and related reactions

Hydroxylation enantioselective reactions with alkenes

Hydroxylation reaction mechanism

Hydroxylation reaction, P450 monooxygenase

Hydroxylation reactions phenylalanine

Hydroxylation, Boyland-Sims Elbs reaction

Hydroxylation, Sandmeyer reaction

Hydroxylations reactions catalyzed

Indirect Photolysis in the Atmosphere (Troposphere)— Reactions with Hydroxyl Radical (HO)

Isocyanate reaction with hydroxyls

Isocyanates reaction with hydroxyl groups

Isoprene hydroxyl radical reaction

Lactams, reaction with enzymes, hydroxylation

Ligand reaction with surface hydroxyl group

Methane, tropospheric reaction with hydroxyl

Methanol hydroxyl radical reaction

Methyl radical reaction with hydroxyl

Microsomes hydroxylation reactions

Monosaccharides hydroxyl groups, reaction with benzyl

Nitro compounds reaction with hydroxyl radical

Nitroalkenes 3-hydroxylation reactions

Nitrous acid hydroxyl radical reaction

Nokami hydroxylative Knoevenagel reaction

Nonhydrolytic hydroxylation reaction

Oxidative reactions alkyl hydroxylation

Oxidative reactions aryl hydroxylation

Oxygen hydroxylation reactions

Oxygen-containing compounds hydroxyl radical reaction

Peracetic acid, trifluoroanti hydroxylation Baeyer-Villiger reaction

Petroleum reactions with hydroxyl radical

Phenol hydroxylation reaction pathway

Phenolic hydroxyl group Reaction

Polyols, hydroxyl groups, reaction with

Prdvost reaction hydroxylation

Prolines 3-hydroxylation reactions

Propane reaction with hydroxyl radicals

Pyrolysis hydroxyl reaction with

Rate constants hydroxyl radical reactions

Reaction LXXII.—Replacement of the Diazonium Group by Hydroxyl

Reaction Replacement of Halogen Atoms by Alcoholic Hydroxyl Groups

Reaction, methane + hydroxyl

Reactions in Hydroxylic Solvents

Reactions of Hydroxyl Containing Polymers with Amino I Formaldehyde Resins

Reactions of the Hydroxyl Group

Replacement, aldehyde group by hydroxyl diazo reaction)

Replacement, aldehyde group by hydroxyl reaction)

Stereoselective hydroxylation reactions

Stereoselective hydroxylation reactions dihydroxylation

Stereoselective hydroxylation reactions isolated enzymes

Stereospecific reactions hydroxylation of alkenes

Sulfuric acid reaction with hydroxyl radicals

Swern oxidation hydroxylation reactions

The Reaction Between Methane and Hydroxyl Radical

Triphenylmethyl chloride reaction with hydroxyl groups

Unexpected Hydroxylation Reactions

Urethane-forming hydroxyl-amino coupling reactions

Wittig reaction hydroxyl directed

Xanthine oxidoreductase hydroxylation reactions

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