Cysteine compounds

Cysteine reduces vanadium(V) 803 the kinetics have been studied.804 V02+-cysteine compounds form in the reduction of vanadium(V) with an excess of cysteine805 and a Chinese publication reports K[V0(HCys0)(H20)]S04 and cis- and frans-K2[VO(CysO)2] (H2CysO = cysteine), and ESR as a function of pH. A purple complex from a 5 1 mixture of cysteine... 

Vanadium compounds have an inhibitory effect against induced rat hepatocar-cinogenesis by limiting cell proliferation and chromosomal aberrations in the pre-neoplastic stages of the development of this cancer [169], These antineoplastic effects of vanadium could be related to the induction of apoptosis and selective DNA damage in tumor cells [170], Vanadate has also proven effective against induction of colon carcinomas [171]. A vanadium(III) cysteine compound has been shown to... 

Papaioannou, A., M. Manos, S. Karkabounas, R. Liasko, A.M. Evangelou, I. Correia, V. Kalfakakou, J.C. Pessoa, and T. Kabanos. 2004. Sobd state and solution studies of a vanadium(III)-L-cysteine compound and demonstration of its antimetastatic, antioxidant and inhibition of neutral endopeptidase activities. J. Inorg. Biochem. 98 959-68. 

Values of specific rotation are expressed as in equation (3) for the amino acid cysteine (compound 30 in the Problems section of this chapter) ... 

Unlike sulfenyl iodides or sulfenyl thiocyanates derived from cysteine compounds, which react readily with cysteine, as well as with its thioethers, hemithioacetals, and 5-acetamidomethyl derivatives, the 5 carbomethoxysulfenyl derivatives generate unsymmetrical disulfides only when treated with free thiols, thus are more selective in their reactivity towards sulfur nuclophiles. With respect to solvents, chloroform is a frequent choice (especially in the presence of free carboxyl groups, see above). When esterification is not a concern, methanol is frequently used. Good results (79% yield) are obtained with a mixture of chloroform/methanol (1 1) for the reaction described in eq 5. For the same reaction, using 7V,7V-dimethylacetamide as a solvent dramatically slows down the reaction, whereas the use of dimethylformamide not only drastically reduces the product yield... 

Patchornik and coworkers studied the elimination reactions of S-2,4-dinitrophenyl-cysteine compounds 390, 391). The method proved suitable for the conversion of cysteine peptides into dehydroalanine peptides, in which the double bond can then be exploited as the site of attack in the specific (hydrolytic or oxidative) cleavage of the peptide 298—300). 

Sulfur. Sulfur is present in every cell in the body, primarily in proteins containing the amino acids methionine, cystine, and cysteine. Inorganic sulfates and sulfides occur in small amounts relative to total body sulfur, but the compounds that contain them are important to metaboHsm (45,46). Sulfur intake is thought to be adequate if protein intake is adequate and sulfur deficiency has not been reported. Common food sources rich in sulfur are Hsted in Table 6. 

Although molybdenum is an essential element, excess levels can have deleterious effects. The LD q and TLV values of the most common Mo compounds are Hsted in Table 3 (63,64). In general the toxicity of Mo compounds is considered to be low. For example, M0S2 has been found to be virtually nontoxic even at high levels. Certain Mo compounds such as MoCl and Mo(CO), have higher toxicity because of the chemical nature and reactivity of these compounds rather than the Mo content. Supplementary dietary Cu ", thiosulfate, methionine, and cysteine have been shown to be effective in alleviating Mo toxicity in animals. 

Organosulfur Adsorbates on Metal and Semiconductor Surfaces. Sulfur compounds (qv) and selenium compounds (qv) have a strong affinity for transition metal surfaces (206—211). The number of reported surface-active organosulfur compounds that form monolayers on gold includes di- -alkyl sulfide (212,213), di- -alkyl disulfides (108), thiophenols (214,215), mercaptopyridines (216), mercaptoanilines (217), thiophenes (217), cysteines (218,219), xanthates (220), thiocarbaminates (220), thiocarbamates (221), thioureas (222), mercaptoimidazoles (223—225), and alkaneselenoles (226) (Fig. 11). However, the most studied, and probably most understood, SAM is that of alkanethiolates on Au(lll) surfaces. 

Several mucolytics reduce the viscosity of mucus by cleaving the disulfide bonds that maintain the gel stmcture. AJ-Acet l-L-cysteine [616-91 -1] (19), introduced in 1963, and mesna [19677-45-5] (20), developed in Europe in the early 1970s (20,21), are effective compounds in this class. Whereas most mucolytics must be adrninistered by aerosol, carbocysteine [638-23-6] (21), which contains a derivatized sulfhydryl group, has shown activity by the oral route (22,23). However, carbocysteine does not reduce mucus viscosity, as does acetylcysteine, but appears to have a direct action on mucus glycoprotein production (24). 

This S-nitroso group is in equilibrium with other S-nitroso compounds formed by reaction of NO with small-molecule thiols such as free cysteine or glutathione (an isoglutamylcysteinylglycine tripeptide) ... 

In the rosary pea Abrus precatorius L. Trigollenine as well as its gallic acid ester Precatorine (209) is found (71P195) (Scheme 69). 1-Carboxymethyl-nicotinic acid (210) was isolated as a colorless solid from the marine sponge Anthosigmella cf. raromicrosclera as a cysteine protease inhibitor (98JNP671). This compound was first synthesized in 1991. The sodium... 

The mixture of free amino acids is reacted with OPA (Fig. 7-8) and a thiol compound. When an achiral thiol compound is used, a racemic isoindole derivative results. These derivatives from different amino acids can be used to enhance the sensitivity of fluorescence detection. Figure 7-9 shows the separation of 15 amino acids after derivatization with OPA and mercaptothiol the racemic amino acids may be separated on a reversed-phase column. If the thiol compound is unichiral, the amino acid enantiomers may be separated as the resultant diastereomeric isoindole compound in the same system. Figure 7-10 shows the separation of the same set of amino acids after derivatization with the unichiral thiol compound Wisobutyryl-L-cysteine (IBLC). 

Oxytocin is a cyclic compound containing a disulfide bridge between two cysteine residues. 

S-adenosyl-L-methionine (AdoMet, SAM) is a cofactor and the most important donor of the methyl (CH3-) group for methyltransferases, including COMT. When the methyl-group has been transferred, the remaining demethylated compound is called S-adenosyl-L-homo-cysteine. 

Rhinoviruses, which represent the single major cause of common cold, belong to the family of picornavimses that harbors many medically relevant pathogens. Inhibitors of the 3C protease, a cysteine protease, have shown good antiviral potential. Several classes of compounds were designed based on the known substrate specificity of the enzyme. Mechanism-based, irreversible Michael-acceptors were shown to be both potent inhibitors of the purified enzyme and to have antiviral activity in infected cells. 

If reaction 49 is responsible for the high decomposition yield of ASCO, it can be understood why it does not occur for PSCO, since the C—H bond strength in the allyl compound is weaker than in the propyl derivative due to the resonance stabilization of the radical60. However, the yield of alanine was found to be 1.97 in the case of radiolysis of PCSO and almost zero for ACSO. Thus reaction 49 does not occur for the case of ACSO. Since only the yields of cysteine (0.98 for ACSO and 0 for PCSO) are given, no explanation can be proposed for the high decomposition yield of ACSO. 

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