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Several gold(I) complexes with cysteine-containing dipeptides have been prepared starting from cystine by coupling different amino acids and using several orthogonal protections. The first step is the reaction of cystine, where the sulfur centre is protected as disulfide, with Boc2 O in order to protect the amino group, followed by coupling of an amino acid ester; finally the disulfide bridge is broken with mercaptoethanol to afford the dipeptide derivative. Further reaction with [AuCl(PPh3 )] gives the gold-dipeptide-phosphine species. Starting from these formally gold(I) thiolate-dipeptide phosphine complexes with the general formula [Au(SR)(PR3 )] different structural modifications, such as change in the type of the amino protecting group, the type of phosphine, the number of gold(I) atoms per molecule, or the use of a non-proteinogenic conformationally restricted amino acid ester, were introduced in order to evaluate their influence in the biological activity of the final complexes. The cytotoxic activity, in vitro, of these complexes was evaluated against different tumour human cell lines (A549, MiaPaca2 and Jurkat). The complexes show an outstanding cytotoxic activity with IC50 values in the very low micromolar range. Structure-activity relationship studies from the complexes open the possibility of designing more potent and promising gold(I) anticancer agents.

Several gold(I) complexes containing a thiolate ligand functionalised with several amino acid or peptide moieties of the type [Au(SPyCOR)(PPh2R')] (where R = OH, amino acid or dipeptide and R' = Ph or Py) were prepared. These thiolate gold complexes bearing biological molecules possess potential use as antitumor agents. Cytotoxicity assays in different tumour cell lines such as A549 (lung carcinoma), Jurkat (T-cell leukaemia) and MiaPaca2 (pancreatic carcinoma) revealed that the complexes exhibit good antiproliferative activity, with IC50 values in the low micromolar range. Several structural modifications such as in the type of phosphine, number of metal atoms and amino acid (type, stereochemistry and functionalisation) were carried out in order to establish the structure-activity relationship in this family of complexes, which has led to the design of new and more potent cytotoxic complexes. Observations of different cellular events after addition of the complexes indicated the possible mechanism of action or the biological targets of this type of new gold(I) drug.

Thiazolium salts 2a-b derived from a dipeptide Boc-Gly-(Thz-Ala)-OMe (1b) containing the nonproteinogenic amino acid L-thiazolylalanine (Thz-Ala) can be used to generate the corresponding N,S-heterocyclic carbene (NSHC) gold(I) (3ab) and silver(I) (4) complexes. Reaction of the NSHC-gold(I) iodide 3b with Boc-Cys-Gly-OMe gives access to the peptide bioconjugate 5, which contains a NSHC-Au-(S-Cys) unit. Compounds 3-5 constitute the first coin metal NSHC-peptide complexes. All new compounds were comprehensively characterized by 1 H, 13 C and 2D-NMR spectroscopy, IR spec-[a] 2517 (B) (C β,ThzAla H 2 ), 41.3 (A) and 40.9 (B) [C α,Gly (dip)H 2 ], 36.8 (B) and 30.3 (A) (C β,Cys H 2 ), 28.3 (C Boc H 3 ) and 16.4 (NCH 2 CH 3 ) ppm. HRMS (ESI + ): m/z calcd. for [M + H] + 860.2268; found: 860.2292.Cell Culture: Jurkat (leukaemia) and MiaPaca2 (pancreatic carcinoma) cell lines were maintained in RPMI 1640, whereas A549 (lung carcinoma) cells were grown in DMEM (Dulbecco's Modified Eagle's Medium). Both media were supplemented with 5 % fetal bovine serum (FBS), 200 U/mL penicillin, 100 μg/mL streptomycin, and 2 mm l-glutamine. Media for A549 cells were also supplemented with 2.2 g/l Na 2 CO 3 , 100 μg/mL pyruvate, and 5 mL nonessential amino acids (Invitrogen). Cell cultures were maintained in a humidified atmosphere of 95 % air/5 % CO 2 at 37°C. Cytotoxicity Assay by MTT:The MTT assay was used to determine the cell viability as an indicator for the sensitivity of the cells to the complexes. [44] Exponentially growing cells were seeded at a density of approximately 1 ϫ 10 5 cells/mL (A549, MiaPaca2) or 3 ϫ 10 5 cells/mL (Jurkat), in a 96-well flat-bottomed microplate and, after 24 h, they were incubated with the compounds. The complexes were dissolved in DMSO and tested in concentrations ranging from 0.5 to 100 μm and in quadriplicate. Cells were incubated with the test compounds for 24 h at 37°C, then, 10 μL/well of MTT (5 mg/ mL) was added and plates were incubated for 1-3 h at 37°C. Finally, 100 μL/well iPrOH (0.05 m HCl) was added. The optical density was measured at 570 nm using a 96-well multiscanner autoreader (ELISA). The IC 50 was calculated by nonlinear regression analysis using Origin software (Origin Software, Electronic Arts, Redwood City, California, USA).

Hydroxyl radicals easily oxidize biomolecules such as proteins and DNA. The most abundant oxidative product of DNA is 8-hydroxy 2'-deoxyguanosine (8-OHdG) and this is considered a biomarker of oxidative DNA damage. This work studies the electrochemical behavior of 8-OHdG on electrodes modified with carbon nanotubes dispersed in polyethylenimine. The technique of differential pulse anodic stripping voltammetry (DPASV) enables quantification of 8-OHdG in the presence of its major interferents, such as ascorbic acid and uric acid. We obtained linear calibration plots in the range from 5.0 10 À7 M to 3.0 10 À5 M, with detection limit (DL) of 1.0 10 À7 M and the quantification limit (QL) of 3.0 10 À7 M.

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The reaction of the gold(I) complex [Au(SpyCOOH)(PPh3)], which contains nicotinic acid thiolate, with several amino acid esters such as glycine methyl ester or the enantiomerically pure L isomers of alanine methyl ester, phenylalanine methyl ester, valine methyl ester, methionine methyl ester, and proline methyl ester produces the gold(I) derivatives with the new thiolate containing amino acid ester ligands [Au{SpyCONHCH(R)COOMe}(PPh3)]. The reaction of these amino acid ester derivatives with LiOH in methanol and acidification with KHSO4 until pH 3-4 afford the corresponding acids, which are water-soluble species. These amino acid compounds can be further coupled with other amines, such as, for example, isopropylamine, to give the corresponding amide derivatives. The species with glycine methyl ester and valine methyl ester have been characterized by X-ray crystallography, showing, in the second case, only one of the enantiomers, which proves that retention of the configuration after reaction occurs.

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