Sulfhydryl group, analysis

RG Hiskey. Sulfhydryl group protection in peptide synthesis, in The Peptides Analysis, Synthesis, Biology, Vol. 3, pp 137-167, Academic Press, New York, 1981. 

Covalent protein adducts of quinones are formed through Mchael-type addihon reachon with protein sulfhydryl groups or glutathione. Metabolic activahon of several toxins (e.g., naphthalene, pentachlorophenol, and benzene) into quinones has been shown to result in protein quinone adducts (Lin et al, 1997 Rappaport et al, 1996 Zheng et al., 1997). Conversion of substituted hydroquinones such as p-aminophenol-hydroquinone and 2-bromo-hydroquinone to their respective glutathione S-conjugates must occur to allow bioactivation into nephrotoxic metabolites (Dekant, 1993). Western blot analysis of proteins from the kidneys of rats treated with 2-bromo-hydroquinone has revealed three distinct protein adducts conjugated to quinone-thioethers (Kleiner et al, 1998). 

Weiner, I. M., and O. H. Muller Interference of Sulfhydryl Groups in Analysis of Urinary Mercury and its Elimination. Anal. Chem. 27, 149 (1955). 

Crystallographic studies of native cysteine proteinases and enzyme-inhibitor complexes have been used to interpret much or the kinetic data for cysteine protemsse-caUlyzed hydrolysis of amide bonds. Analysis of the crystal structures of papain [16]. caricain [38], actinidain [56], etc. shows that these structures are closely related. The active site of all these cysteine proteinases contains the Cys-25 sulfhydryl group in close proximity to the His-159 imidazole ring nitrogens, where the latter can abstract the sulfhydryl proton to facilitate attack on the substrate amide carbonyl group [17]. 

Sulfhydryl groups/disulfide bridges Glycan analysis Peptide mapping (under reducing and nonreducing conditions)... 

According to Kagi and Vallee (1961), at least 95% of all of the sulfur of this protein is present in the form of sulfhydryl groups of cysteine further, the cysteine content of this protein is of the order of 30%. By chemical analysis, practically no aromatic amino acids are found in this protein, and this is clearly reflected in the spectrum. It is worth noting that Cd bound to this protein effects a substantial and specific increase in absorptivity around 2500 A. 

Under the above conditions, the modification is totally restricted to sulfhydryl groups (Heinrikson 1971).S-methylcysteine is quantitated by amino acid analysis after acid hydrolysis ( 2.5.5). 

Spectroscopic techniques as well have been used in demonstrating an interaction between CaD and CaT (Mani and Kay, 1990). For fluorescence studies, the sulfhydryl groups in CaD were labeled with acry-lodan. Addition of CaT to labeled CaD in the presence of Ca + produced nearly 50% increase in fluorescence intensity and the emission maximum shifted to 492 nm from 504 nm. Labeled CaD was titrated with CaT. Analysis of the titration curve by curve fitting showed that the best fit was obtained when the molar ratio of CaT to CaD in the complex at saturation was 1 1. A value of (9 2) X 10 M was obtained from the titration. However, there was no evidence of any interaction between CaT and CaD in the absence of Ca2+. 

Because an analysis for amino acids in an acid hydrolysate of a protein gives no information about the state of that particular amino acid in the original protein, chemical methods that do not distort the conformation of the protein can thus provide information on the state of the side chain of that particular amino acid in the protein in solution or in a crystal state. Thus, poorly reactive (sometimes called masked ) sulfhydryl groups of cysteine show different degrees of reactivity, depending upon the chemical agents used (Table III). 

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