Cysteine -, selective

Butyl chloroformate reacts with cysteine to protect both the amine and thiol groups as with N,S-bis(benzyloxycarbonyl)cysteine, selective or simultaneous removal of the N- or S-protective groups can be effected.1... 

A specific P-globin adduct to Cys93 and Cysll2 was identified by the use of electrospray tandem mass spectrometry as well as by chemical transformation with the cysteine-selective reagent vinylpyridine and derivatization by S-carbamylation (Fidder et al, 2000). No method for quantification of this adduct was described. As of mid-2008, no specific adducts other than the above mentioned have been described in the literature. 

Sellke FW, Tomanek RJ, Harrison DG. L-cysteine selectively potentiates nitroglycerin-induced dilation of small coronary microvessels. J Pharmacol Exp Ther 1991 258(1) 365-9. 

Many proteins have been labeled with organometallic complexes, mostly for analytical purposes. Some of those are mentioned in Section 1.31.5 of this chapter, and the topic has been comprehensively reviewed by Salmain. Ryabov published an earlier review on the topic.The labeling techniques are mostly the same as for organic derivatives, that is, cysteine-selective reactions (maleiimides, acetic acid halogenides), activated acids, aldehydes, or thiocyanates that react with lysines, biotin-(strept)avidine labeling, and others. 

C-Sox was able to coordinate the phosphate-bound Mg without the predisposed P-turn-mediated conformational bias. Synthesis of both Fmoc-protected C-Sox (4) and Sox-Br (5) allowed for facile incorporation into peptides via either SPPS or cysteine-selective alkylation, respectively, (Figure 1.5) [20]. This increasingly versatile approach allowed recognition elements on both sides of the phos-phorylatable residue to be included in the peptidic sensor, generally resulting in superior kinase specificity and selectivity. 

The sulfhydiyl group in cysteine can be selectively protected in the presence of the amino group by reaction with 2,4-dinitrophenol at pH 5-6. ... 

When cysteine reacts with an alkyl or aiyl chloroformate, both the —SH and —NH groups are protected as a thiocarbonate and as a carbamate, respectively. Selective or simultaneous removal of the protective groups is possible. 

InHBr, AcOH, 25°, 30min. The5-Cbzgroup is removed slowly under these conditions, but the N-Cbz group is completely cleaved, thus providing some selectivity in the protection scheme for cysteine. 

It is now apparent that bacteria have developed resistance to heavy metals and the detoxifying process is initiated and controlled by metallo-regulatory proteins which are able selectively to recognize metal ions. MerR is a small DNA-binding protein which displays a remarkable sensitivity to Hg +. The metal apparently binds to S atoms of cysteine and this has been a major incentive to recent work on Hg-S chemistry. 

British investigators (Haddow and Timmis 1951) synthesized and studied esters of the methanesulfonic acid. The most active derivative was the dimethylsulfonic ester of 1,4-butanedione, known as busulfan. Busulfan interacts with the thiol groups of proteins and amino acids some of its metabolites can alkylate the thiols of cysteine, peptides and proteins. Busulfan exerts selective cytotoxic activity in hematopoietic bone marrow cells and inhibits the formation of granulocytes and platelets. It slightly affects the lymphoid tissue. 

The Strecker reaction has been performed on the aldehyde 182 prepared from L-cysteine [86] (Scheme 28). The imine was formed in situ by treatment with benzylamine, then TMS cyanide was added to afford prevalently in almost quantitative yield the syn-diamine 183, which is the precursor of (-l-)-biotin 184. The syn selectivity was largely affected by the solvent, toluene being the solvent of choice. Since the aldehyde 182 is chemically and configurationally unstable, a preferred protocol for the synthesis of 183 involved the prehminary formation of the water-soluble bisulfite adduct 185 and the subsequent treatment with sodium cyanide. Although in this case the syn selectivity was lower, both diastereomers could be transformed to (-l-)-biotin. 

It is not only the activity that can be altered by incorporation of noncoded amino acids. Introduction of structures possessing certain chemical functions leads to the possibility of highly regioselective modification of enzymes. For example, selective enzymatic modification of cystein residues with compounds containing azide groups has led to the preparation of enzymes that could be selectively immobilized using click chemistry methods [99]. 

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