Gold complexes with cysteine

Chernyak, A. S. and Shestopalova, L.F. (1976) Study of complexes of gold(I) with cysteine in an alkaline medium. Russian Journal of Inorganic Chemistry, English Translation, 21, 464—465. 

Possible metabolites previously suggested include gold complexes of cysteine and glutathione ( ). We have examined solid samples of each of these and find them to fit satisfactorily to a model in which gold is coordinated to two bridging sulfur atoms with bond lengths identical to those found in the chronic sodium gold(I)thiomalate aurosomes. 

The anticq>ated sur ce structure of the L-cysteine SAM on gold and its conq>lex witii Cu is shown in Figure 8. Electrochemical and XPS data suggest one Cu per two cysteine ligands (23). Literature reports indicate that the best complexation performance for tiie electrochemical sensors was at pH = S, the isoelectric point of L-cysteine. Similar optimal performance at pH = S was also observed for microcan ever deflection experiments. The deflection anq>litude caused by Cu complexation with the L-cysteine monolayer was much less for experiments performed at pH = 3 or pH = 7, than at pH = 5. 

Figure 8. Schematic representation of the molecular structure of the L cysteine self-assembled monolayer on the gold surface of the microcantilever and its complexation with Cu. ...

Nolan and coworkers reported the cytotoxicity of different neutral and cationic complexes. The first series of systems studied were Au-IPr derivatives bearing biocompatible moieties such as amino acids (L-proline or L-cysteine, Figure 7.16) [17]. In parallel, a second series of systems was selected, as it is well-known in the literature that cationic gold complexes can induce apoptosis of cancer cell lines. The IC50 were measured with LNCaP (prostate carcinoma) and MDA MB231 (breast carcinoma). 

The vast majority of intravascular gold is protein bound, and most of this (> 85%) is bound to albumin, with the remainder linked to globulin moieties. Gold complexes bind to many proteins with inhibition of activity, and the reactions have been extensively tabulated [10]. Studies on bovine serum albumin (BSA) confirmed, both for AuSTM and AF, that the binding site was the unique cysteine residue, Cys34 [31, 32, 33]. The PEt3 of AF is not lost [32, 33] and the reaction is best considered as a thiol displacement ... 

Cat B is an abundant and ubiquitously expressed cysteine peptidase of the papain family and makes up a major fraction of lysosomal enzymes that is capable of degrading components of the extracellular matrix in various diseases [30-32]. Cat B is also a prognostic marker for several types of cancer [33], and increased expression and secretion of cat B has been shown to be involved in the migration and invasion of various tumours [34—36], The precise role of cat B in solid tumours is not fully understood, but it has been proposed to participate, along with other cysteine cathepsins, in metastasis, angiogenesis, and tumour progression [37], Indeed, cat B inhibitors reduce both tumour cell motility and invasiveness in vitro [38], Recently, metal complexes based on rhenium, gold and palladium were shown to be effective inhibitors of cat B [39-44],... 

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