Formation from sulfite oxidation

Addition of AMP to the sulfite-treated APS reductase resulted in further bleaching between 350 and 500 nm. Peck et al. (S8S, S8S) have shown by EPR spectroscopy near liquid helium temperature that addition of either sulfite or AMP alone does not result in the formation of an iron signal at g = 1.94. However, when AMP and sulfite are added together, a g = 1.94 signal is produced, which is approximately 80 of that obtained when the enzyme is reduced with dithionite. Thus, the authors suggested that APS reductase catalyzes an intramolecular electron transfer during sulfite oxidation as shown in Fig. 42 from Peck et al. iS8S). 

Synthesis of Sulfur Amino Acids. Of the many oxidation states of sulfur, only sulfite has been shown to be utilized by cell-free systems in the net synthesis of compounds with carbon-sulfur bonds, although mutant studies have indicated that more reduced forms can be incorporated. The formation of cysteinesulfinic acid from sulfite has been demonstrated in extracts of acetone-dried rabbit kidney it is possible that this reaction participates in the principal mechanism of sulfur incorporation. In many organisms that require preformed sulfur amino acids, cysteine may be formed from methionine. Only the sulfur of methionine is transferred to cysteine the carbon skeleton of cysteine is derived exclusively from serine. Transsulfuration appears to require the formation of homocysteine from methionine. Homocysteine and serine condense to form a thioether, cystathionine (V). Pyridoxal phosphate has been... 

Formic acid acts in a similar manner in stabilizing die pH however, it differs from other carboxylic acids used as buffering scents in several important respects (1) it is less expensive than other pure acids on a weight or molar equivalent basis, (2) it can be purchased, stored, and added as a neutral salt such as sodium formate, and (3) it has the unique ability to inhibit sulfite oxidation while improving sulfur dioxide absorption efficiency (Moser et al., 1990). 

Barium sulfide solutions undergo slow oxidation in air, forming elemental sulfur and a family of oxidized sulfur species including the sulfite, thiosulfate, polythionates, and sulfate. The elemental sulfur is retained in the dissolved bquor in the form of polysulfide ions, which are responsible for the yellow color of most BaS solutions. Some of the mote highly oxidized sulfur species also enter the solution. Sulfur compound formation should be minimized to prevent the compounds made from BaS, such as barium carbonate, from becoming contaminated with sulfur. 

The value of this method lies in the fact that formation of elemental selenium is unlikely to occur since the high-valency species such as Se(IV) that could oxidize the selenide ions are absent from solution. The SeSO and SOj ions (or their protonated forms) do not oxidize Se , while any free Se that may be formed would redissolve in sulfite giving selenosulfate again, since the latter is prepared by dissolving Se in excess sulfite. 

Taurine is generally prepared from ox bile1 or the large muscle of the abalone.2 It has been synthesized from isethionic add through chloroethanesulfonic acid followed by the action of aqueous ammonia 3 from ethyleneimine and sulfur dioxide 4 from 2-mercaptothiazoline by oxidation with bromine water 5 from bromoethylamine and ammonium sulfite 6 and from acetaldehyde by a complex set of reactions involving sulfonation, formation of the aldehyde ammonia and the imido sulfonic add and finally reduction.7 The method given in the procedure has recently appeared in the literature.8 9... 

If the snlfate anion-radical is bonnd to the snrface of a catalyst (sulfated zirconia), it is capable of generating the cation-radicals of benzene and tolnene (Timoshok et al. 1996). Conversion of benzene on snlfated zirconia was narrowly stndied in a batch reactor under mild conditions (100°C, 30 min contact) (Farcasiu et al. 1996, Ghencin and Farcasin 1996a, 1996b). The proven mechanism consists of a one-electron transfer from benzene to the catalyst, with the formation of the benzene cation-radical and the sulfate radical on the catalytic snrface. This ion-radical pair combines to give a snrface combination of sulfite phenyl ester with rednced snlfated zirconia. The ester eventually gives rise to phenol (Scheme 1.45). Coking is not essential for the reaction shown in Scheme 1.45. Oxidation completely resumes the activity of the worked-out catalyst. 

Assay procedures for dopamine which are superficially similar to the lutin procedure described above have been reported recently.266-268 The chemistry of the production of the fluorophore from dopamine is, however, somewhat different since the fluorophore is not a 5,6-dihydroxyindoxyl, it is incorrect to refer to the trihy-droxyindole fluorophore of dopamine (cf. ref. 252). Oxidation of the extracted catecholamine is usually carried out with iodine,266-268 presumably with the formation of 7-iodonorepinochrome. The aminochrome is subsequently rearranged to 5,6-dihydroxyindole (it is probable that deiodination accompanies the rearrangement in this case) by a solution of sodium sulfite in aqueous alkali the solution is acidified before measuring the fluorescence of the product (which is said to form relatively slowly and to be very stable).266-268 Irradiation of the reaction mixture with ultraviolet light accelerates the maximal development of fluorescence.266 Since acidification will produce sodium bisulfite in the reaction mixture, it is probable that the fluorophore is a 5,6-dihydroxyindole-sodium bisulfite addition complex. Complexes of this type are known to be both fluorescent and relatively stable in dilute acid solution.118 123,156 265 They also form relatively slowly.255... 

This purification process is quite sensitive to pH (Ref 23). As shown in Fig 6, yield loss rises sharply above pH 7.5, because of the formation of the water-soluble complex of 2,4,6-TNT with Na sulfite. In addition, at pH values above about 8 (see Fig 7 and Table 1), the formation of two by-products [hexanitrobibenzyl (HNBB), and methylpentanitrodiphenylme thane (MFDM)] increases strongly. (The chemical structures and modes of formation of these compds are given in the section on Chemical Reactions and Derivatives ). These compds have an adverse effect on the mode of crystn of TNT, resulting in the formation of cracks and voids in the finished cast expl (Ref 13). It is also apparent from Table 1 that meta TNT isomers are not completely removed, and that the amounts of all of the DNT Isomers and of five of the oxidation products remain unchanged... 

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