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Twelve Pt(ii) complexes with cis-PtP2S2pharmacophores (where P2refers to two monodentate or one bidentate phosphane ligand and S2is a dithiolato ligand) were prepared, characterized and evaluated as potential antiproliferative agents. The various compounds were first studied from the structural point of view; afterward, their solubility properties as well as their solution behaviour were analyzed in detail. Antiproliferative properties were specifically evaluated against A2780 human ovarian carcinoma cells, either resistant or sensitive to cisplatin. For comparison purposes similar studies were carried out on four parent cis-dichloro bisphosphane Pt(ii)complexes. On the whole, the cis-PtP2S2compounds displayed significant antiproliferative properties while the cis-PtP2Cl2(cis-dichloro bisphosphane Pt(ii)) compounds revealed quite poor biological performances. To gain further insight into the molecular mechanisms of these bisphosphane Pt(ii) compounds, the reactions of selected complexes against the model protein cytochrome c were investigated by ESI-MS and their adduct formation explored. A relevant reactivity with cyt c was obtained only for cis-PtP2Cl2compounds, whereas cis-PtP2S2compounds turned out to be nearly unreactive. The obtained results are interpreted and discussed in the frame of the current knowledge of anticancer platinum compounds and their structure–activity-relationships. The observation of appreciable antiproliferative effects for the relatively inert cis-PtP2S2compounds strongly suggests that these compounds will undergo specific activation within the cellular environment. [ABSTRACT FROM AUTHOR]

A series of organometallic compounds of general formula [(arene)M(PTA)nXm]Y (arene = η6-C10H14, η-C5Me5); M = Ru(ii), Os(ii), Rh(iii) and Ir(iii); X = Cl, mPTA; Y = OTf, PF6) have been screened for their cytotoxicity and ability to inhibit cathepsin B in vitro, in comparison to the antimetastatic compound NAMI-A. The Ru and Os analogues and NAMI-A showed similar enzyme inhibition properties (with IC50values in the low μM range), whereas the Rh(iii) and Ir(iii) compounds were inactive. In order to build up a rational for the observed differences, DFT calculations of the metal complexes adducts with N-acetyl-l-cysteine-N′-methylamide, a mimic for the Cys residue in the cathepsin B active site, were performed to provide insights into binding thermodynamics in solution. Initial structure–activity relationships have been defined with the calculated binding energies of the M–S bonds correlating well with the observed inhibition properties of the compounds. [ABSTRACT FROM AUTHOR]

Cuprizone (oxalic acid bis(cyclohexylidene hydrazide)) is a potent neurotoxin that is known to induce the destruction of the myelinic sheath which covers the cells of the central nervous system (CNS). The mechanism of action has not yet been elucidated due to lack of structural information. We have performed an ab initio prediction of the molecular structure by high-level quantum chemical methods, leading to two possible conformers of a nearly identical energy: A, for which an analysis of the electron density distribution shows more propensity for intermolecular bonding, and B, with stronger intramolecular liaison. Having obtained suitable single crystals, we report a detailed study of the crystal and molecular structure, which reveals that the molecular and crystal centers of symmetry coincide, and that the actual conformer is A, as expected, and in agreement with the ab initio prediction. Further information is gained by optimization of the crystal structure by Car-Parrinello molecular dynamics, yielding good agreement with observation. Infrared and Raman spectra show mutual exclusion, suggesting a centrosymmetric molecule with carbonylic bonds in trans configuration; moreover, vibrational frequencies calculated ab initio also show excellent agreement with observations. We thus present a multi-technique approach to the prediction and interpretation of various aspects of the complex interplay between intra- and intermolecular forces. [ABSTRACT FROM AUTHOR]

The protein binding of anticancer metallodrugs is regarded as an important part in their mode of action both for delivering the active moiety into the tumor but also being responsible for deactivation and/or unwanted side effects. Characterization of protein binding and release may allow new drugs to be designed which are devoid of protein interactions or capable of binding selectively to protein targets. Herein, we report the comparison of different ionization techniques, i.e. matrix-assisted laser desorption/ionization (MALDI) and nanoelectrospray ionization mass spectrometry (nESI-MS), for the analysis of small protein–Pt anticancer drug interactions. For this purpose, cisplatin, transplatin and oxaliplatin were incubated with the model protein ubiquitin (Ub) at a molar ratio of 2 : 1 (Pt : Ub) followed by MS analysis. Cisplatin, transplatin and oxaliplatin formed mainly monoadducts with Ub, but of significantly different composition. As reported earlier, cisplatin forms mainly bifunctional Ub–[Pt(NH3)2] adducts, while with transplatin the most abundant adduct was found to be a monofunctional Ub–[Pt(NH3)2Cl] species. Oxaliplatin formed exclusively bifunctional species of the formula Ub–[Pt(chxn)] (chxn = cyclohexane-1,2-diamine). The applied analysis methods provide comparable results. However, the higher resolution of the nESI-quadrupole time-of-flight (QToF)-MS allowed unambiguous characterization of a series of mono- and bis-adducts including Ub–[Pt(NH3)2(H2O)] for both cisplatin and transplatin. Applying nESI-ion trap (IT)-MS showed the advantage of higher sensitivity than the ToF instruments, allowing the detection of bisadducts of oxaliplatin after one week of incubation. In contrast to the ESI mass spectra, MALDI showed a higher degree of fragmentation of the Ub–platinum conjugates. [ABSTRACT FROM AUTHOR]

The tetrapeptide Ac-Gly-[Cys-Sec]-Gly-NH2, reproducing the C-terminal motif of the selenoenzyme thioredoxin reductase, was designed and synthesized, and its reactions with a few medicinally relevant gold(i,iii) compounds investigated by ESI-MS. Remarkably, the main reaction products could be unambiguously identified providing valuable insight into the likely mechanisms of enzyme inhibition by gold compounds. [ABSTRACT FROM AUTHOR]

During the last 50 years, formation of the highly chromogenic copper cuprizone complex has been exploited for spectrophotometric determinations of copper although the precise chemical nature of the resulting species has never been ascertained; we eventually show here, in contrast to current opinion, that copper cuprizone is a copper(iii)complex. [ABSTRACT FROM AUTHOR]