Methionine sulphone

McLafferty rearrangement 133, 163 Meisenheimer complexes 699, 702 Metal-chelated intermediates 838 Metal-halogen exchange 781, 784 Methionine, oxidation of 852-855 Methionine sulphone 853 Methionine sulphoxide 851-869 reduction of 1063 residues of... 

S-Methyl-L-methionine chloride [1115-84-0] M 199.5, [a]Q +33 (0.2M HCl). Likely impurities are methionine, methionine sulphoxide and methionine sulphone. Crystd from water by adding a large excess of EtOH. Stored in a cool, dry place, protected from light. 

Figure 6.8 Experimental variation of the retention of 23 phenylthiohydantoin (PTH) derivatives of amino acids with mobile phase composition in RPLC. Mobile phase mixtures of acetonitrile and 0.05M aqueous sodium nitrate buffer (pH — 5.81). All mobile phases contain 3% THF. Stationary phase ODS silica. Solutes D = aspartic acid C-OH = cysteic acid E = glutamic acid N = asparagine S = serine T = threonine G = glycine H = histidine Q = glutamine R = arginine A = alanine METS = methionine sulphone ABA = a-aminobutyric acid Y = tyrosine P = proline V = valine M = methionine NV = norvaline I = isoleucine F = phenylalanine L = leucine W = tryptophan K = lysine. Figure taken from ref. [610]. Reprinted with permission.

Fig. 11.2.9. Amino acid analysis using a conventional analyser. Chromatographic conditions colunm, Dionex DC-6A (300x4.6 mm I.D.) mobile phase, sodium citrate, three-buffer programme detection, post-column reagent ninhydrin (absorbance 1 full scale). Peaks 1, cysteic acid 2, aspartic acid 3, methionine sulphone 4, threonine 5, serine 6, glutamic acid 7, proline 8, glycine 9, alanine 10, half cystine 11, valine 12, methionine 13, isoleucine 14, leucine 15, Y-leucine 16, tyrosine 17, phenylalanine 18, ammonia 19, lysine 20, histidine 21, arginine. Reproduced from Beckman information catalogue, with permission.

Cysteine Methionine Disulphide bridges Methionine sulphoxide, methionine sulphone Hydroxytrypt(mhan, kynorenine, hydroxy- and formyl-l orenine... 

Since biological value is dependent primarily upon essential amino acid constitution, it would seem logical to assess the nutritive value of a protein by determining its essential amino acid constitution and then comparing this with the known amino acid requirements of a particular class of animal. Application of modern chromatographic techniques coupled with automated procedures allows relatively quick and convenient resolution of mixtures of amino acids. However, the acid hydrolysis used to produce such mixtures from protein destroys practically all the tryptophan and a considerable proportion of the cystine and methionine. Tryptophan has to be released by a separate alkaline hydrolysis, and cystine and methionine have to be oxidised to cysteic acid and methionine sulphone to ensure their quantitative recovery. Losses of amino acids and the production of artefacts, which are greater with foods of high carbohydrate content, are reduced if the hydrolysis is carried out in vacuo. Evaluations of proteins in terms of each individual amino acid would be laborious and inconvenient, and several attempts have been made to state the results of amino acid analyses in a more useful and convenient form. 

The action of performic acid may be taken as an indication that sulphur containing amino-acids are present (it has previously been shown that thioglycollate does not affect the activity therefore cystine is not directly involved ). Examination of an acid hydrolysate of oxidised LRF showed that methionine sulphone was present but cysteic acid was only present in trace amounts. Previous figures for the amino acid content of LRF preparations have not included methionine, and the aromatic amino-acids were reported in trace amounts. 

L(or D)-Methionine sulphone are reversible inhibitors of glutamine synthetase. Incubation of L(or D)-[methyl- C]methionine sulphone with glutamine synthetase in the presence of ATP yields a C-containing product that is tentatively formulated as the isothiazole derivative (74). The assigned... 

Cytochrome c has 4 methionine residues, two of which are covalently linked to the haem moiety One of the other two methionine residues is coordinated to the iron in the axial position The major S 2 p band of the crystalline compound appears at 162.6 eV attributable to the methionine residues. Prolongued irradiation causes an increase of the RSOJ or the sulphate band from 28% to 40% (Table 2). When aqueous cytochrome c is recorded, the amount of oxidised sulphur rises to 63% of the methionine sulphur band. The possible extraneously bound redox active transition metals, probably, have created a metal driven Haber Weiss reaction which led to the marked amount of oxidised sulphur observed. Splitting of the iron-sulphur bonding by cyanide results in dramatic increase of the 167.7 band and the additional appearance of a S 2p signal at 164.3, probably due to RS=0 species. This oxidation is believed to be catalyzed by the haem iron. Hydrogen peroxide alone converts the methionine sulphur completly to sulphonic acid. 

Radiolabelling is often performed by oxidation of iodide by different agents for iodination of tyrosine and histidine residues in peptides. However, unfavourable oxidation reactions can occur simultaneously, e.g., cysteine and methionine can be oxidized to their corresponding sulphone or sulphonic acid, so that neutral amino acids are converted to highly acidic groups, thus changing the electrostatic distribution within the structme of the... 

Methionine also represents an important and early target for oxidation, where end products include the sulphoxide and the sulphone. In addition to the hydroxyl radical, hypochlorous acid, nitric oxide and singlet oxygen are all capable of eliciting this change. 

Chick embryo utilizes 35S-sulphate for the synthesis of 35S-taurine, but the amount of sulphate-sulphur present in the unincubated egg is insufficient to furnish S necessary for the taurine synthesized. Injection167 of L-methionine-35S or of L-cysteine HCl-35S into the egg white, and determination of the distribution of 35S in the chick hatched from the incubated egg revealed that with [35S]cysteine 10% of the administered 35S is located in the chick as taurine, 12% as sulphate, 1.3% as methionine and 49% as cystine. With methionine-35S 9.1% was recovered as taurine, 10% as sulphate, 43% as cystine and 35% as methionine. These findings indicate that methionine is converted to cystine during embryonic development, but significant amounts of cysteine-35S were incorporated also into methionine. Possibly, trans-sulphonation from methionine to cysteine is reversible to some extent in the chick embryo, similarly to what has been found in young rats168. 

As a photochemical oxidation product of DMS (Bentley et al., 1971) dimethyl sulphoxide may be detected in seawater which has been reported to inhibit photosynthesis in algae (Cheng et al., 1972). Methionine and biotin sulphoxides are oxidation products of methionine and biotin respectively, while microorganisms have been reported which reduce these compounds as well as DMDS (Zinder and Brock, 1978b). These authors also comment on the chemical stability of the sulphones. The methyl sulphones which have been identified in Baltic seal by Jensen and Jansson (1976) are, however, metabolically produced from PCB and DDE within the animal. 

The oxidative reactivities of silver(ii) and silver(m) have been compared. The first- and second-order terms in [Ag ] in various reactions have been assessed and an attempt has been made to resolve the apparent reverse of reactivity between the bi-and ter-valent silver ions, depending on the substrate. A reaction scheme for the oxidation of water has been presented and the data are consistent with a reactive dimeric form of Ag. The hydrolysis constant of Ag is also considered to be less than 31 mol . The properties of octaethylporphyrins show the Agi complex to be stable,and cyclic voltammetric studies show reversibility in the +3<- +2 redox steps. In the gold(m) (as AuCl4 ) oxidation of methionine, there is stereospecificity in the reaction, the product being the corresponding sulphoxide with no evidence for a sulphone. The reaction is biphasic, with an initial complex formation which is too rapid for study by conventional techniques followed by a slower intramolecular redox reaction leading to gold(i). The rate of this latter process is dependent on the methionine concentration. The oxidation also takes place when the substrate is part of a peptide chain. 

Hexane. 3500—1300 cm. Thin film 2-Methylpentane. 3500—1300 cm . Thin film Dec-l-ene. 3500—1300 cm. Thin film /rfl 5-Stilbene. 1300—400 cm". KBr disc Styrene. 3500—1300 cm". Thin film Styrene 1300—400 cm". Thin film Phenyl Acetylene. 3500—1300 cm". Thin film Phenyl Acetylene. 1300—400 cm". Thin film Aromatic substitution patterns. 2000—1600 cm" para-Cresol. 3500—1300 cm". I.M. CCI4 solution tert-Butyl methyl ketone. 4000—650 cm". Thin film -Heptaldehyde. 4000—650 cm". Thin film Di-/sopropyl ether. 4000—650 cm". Thin film Acetic Anhydride. 4000—650 cm". Thin film Propionic acid. 4000—650 cm". Thin film Propionic acid. 3500—2000 cm". Solution 0.005M CCI4 Methyl salicylate. 4000—650 cm . Thin film n-Butylamine. 4000—650 cm". Thin film Benzamide. 3500—1300 cm". KBr disc Methionine. 4000—650 cm". KBr disc Benzonitrile. 3500—1300 cm". Thin film Benzonitrile. 1300—400 cm". Thin film A-Methyl acetamide. 3500—650 cm". Thin film Methyl acrylate. 4000—650 cm". Thin film Benzoyl chloride. 4000—650 cm". Thin film Triphenyl phosphate. 3500—1300 cm". Melt Triphenyl phosphate. 1300—400 cm". Melt Di-wopropyl sulphone. 4000—650 cm". Melt Nitrobenzene. 4000—650 cm". Thin film Dimethyl sulphoxide. 4000—650 cm". Thin film Polymeric silicone. 4000—650 cm". Thin film Calcium sulphate Dihydrate. 4000—650 cm". KBr disc... 

Oxidation of sulphides with HjOz to sulphones is catalysed by ZrCU or Zr(N03)4, while trichloroisocyanuric acid converts methionine residues in peptides into the sulphone (though with some destruction of other readily oxidized amino-acid residues). ... 

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