Proteins halogenation reaction

Although the primary utility of active halogen compounds is to modify sulfhydryl groups in proteins or other molecules, the reaction is not totally specific. Iodoacetyl (and bromoacetyl) derivatives can react with a number of functional groups within proteins the sulfhydryl group of cysteine, both imidazolyl side chain nitrogens of histidine, the thioether of methionine, and... 

This iron-sulfur oxygenase [EC 1.14.12.11] catalyzes the reaction of molecular oxygen with toluene and NADH to produce (15 ,27 )-3-methylcyclohexa-3,5-diene-l,2-diol and NAD. This reductase is an iron-sulfur flavo-protein (FAD) that contains ferredoxin. Ethylbenzene, 4-xylene, and some halogenated toluenes can likewise undergo conversion to the corresponding cw-dihydro-diols. 

Heinrikson et al. (161) have extended the study of the reaction at pH 5.5 to a series of halo acids, investigating the effect of chain length, d and l antipodes, and the position of the halogen substituent. All of the alkylated products showed enzymic activities of less than 0.5%. A summary of the rates of reaction of the various compounds with both His 12 and 119 and free histidine are shown in Table VII. All of the reagents react more rapidly with the protein than with free histidine. 

Bromoethylamine may undergo two reaction pathways in its modification of sulfhydryl groups in proteins (Fig. 84). In the first scheme, the thiolate anion of cysteine attacks the No. 2 carbon of 2-bromoethylamine to release the halogen and form a thioether bond (Lindley, 1956). This straightforward reaction mechanism is similar to the modification of sulfhydryls with iodoacetate (Section 4.2). In a two-step, secondary... 

The reaction of IODO-GEN with iodide ion in solution results in oxidation with subsequent formation of a reactive, mixed halogen species, IC1 (Fig. 266). Either 125I or 13 1 can be used in this reaction. The IC1 then rapidly reacts with any sites within target molecules that can undergo electrophilic substitution reactions. Within proteins, any tyrosine and histidine side-chain groups can be modified with iodine within... 

Industrial fluid-fluid reactors may broadly be divided into gas-liquid and liquid-liquid reactors. Gas-liquid reactors typically may be used for the manufacture of pure products (such as sulfuric acid, nitric acid, nitrates, phosphates, adipic acid, and other chemicals) where all the gas and liquid react. They are also used in processes where gas-phase reactants are sparged into the reactor and the reaction takes place in the liquid phase (such as hydrogenation, halogenation, oxidation, nitration, alkylation, fermentation, oxidation of sludges, production of proteins, biochemical oxidations, and so on). Gas purification (in which relatively small amounts of impurities such as C02, CO, COS, S02, H2S, NO, and... 

These kinetics data are consistent with a preequilibrium dissociation of dmf from the molybdenum center to form a reactive five-coordinate species that rapidly reduces the Fe(III) center via an inner sphere (halogen transfer) reaction. Other one-electron atom transfer reactions are known in oxo-molybdenum chemistry (262). An innersphere (atom transfer) mechanism is not a viable model for intramolecular transfer in sulfite oxidase because in the enzyme the Mo and Fe centers are almost certainly held too far apart by the protein framework. Moreover, the 65-type heme center of sulfite oxidase is six-coordinate with axial histidine ligands from the protein and hence cannot participate in atom transfer reactions. 

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