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Two cationic ruthenium(II) 1,4,7-trithiacyclononane ([9]aneS 3 ) complexes of curcumin (curcH) and bisdemethoxycurcumin (bdcurcH), namely [Ru(curc)(dmso-S)([9]aneS 3 )]Cl (1) and [Ru(bdcurc)(dmso-S)([9]aneS 3 )]Cl (2) were prepared from the [RuCl 2 (dmso-S)([9]-aneS 3 )] precursor and structurally characterized, both in solution and in the solid state by X-ray crystallography. The corresponding PTA complexes [Ru(curc)(PTA)([9]aneS 3 )]Cl (3) and [Ru(bdcurc)(PTA)([9]aneS 3 )]Cl (4) have been also synthesized and characterized (PTA = 1,3,5-triaza-7-phosphaadamantane). Bioinorganic studies relying on mass spectrometry were performed on complexes 1-4 to assess their interactions with the model protein lysozyme. Overall, a rather limited reactivity with lysozyme was highlighted accompanied by a modest cytotoxic potency against three representative cancer cell lines. The moderate pharmacological activity is likely connected to the relatively high stability of these complexes., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Soft metal ions can inactivate urease, a Ni(II)-dependent enzyme whose hydrolytic activity has significant implications in agro-environmental science and human health. Kinetic and structural studies of the reaction of Canavalia ensiformis urease (JBU) and Sporosarcina pasteurii urease (SPU) with Ag(I) compounds of general formula [Ag(PEt 3 )X] 4 (X = Cl, Br, I), and with the ionic species [Ag(PEt 3 ) 2 ]NO 3 , revealed the role of the Ag(I) ion and its ligands in modulating the metal-enzyme interaction. The activity of JBU is obliterated by the [Ag(PEt 3 )X] 4 complexes, with IC 50 values in the nanomolar range; the efficiency of the inhibition increases in the Cl - < Br - < I - order. The activity of JBU upon [Ag(PEt 3 ) 2 ]NO 3 addition decreases to a plateau corresponding to ca. 60% of the original activity and decreases with time at a reduced rate. Synchrotron X-ray crystallography on single crystals obtained after the incubation of SPU with the Ag(I) complexes yielded high-resolution (1.63-1.97 Å) structures. The metal-protein adducts entail a dinuclear Ag(I) cluster bound to the conserved residues αCys322, αHis323, and αMet367, with a bridging cysteine thiolate atom, a weak Ag … Ag bond, and a quasi-linear Ag(I) coordination geometry. These observations suggest a mechanism that involves the initial substitution of the phosphine ligand, followed by a structural rearrangement to yield the dinuclear Ag(I) cluster. These findings indicate that urease, in addition to the active site dinuclear Ni(II) cluster, possesses a secondary metal binding site, located on the mobile flap domain, capable of recognizing pairs of soft metal ions and controlling catalysis., (Copyright © 2021. Published by Elsevier Inc.)

Arsenoplatin-1 (AP-1), the prototype of a novel class of metallodrugs containing a PtAs(OH) 2 core, was encapsulated within the apoferritin (AFt) nanocage. UV-Vis absorption spectroscopy and inductively coupled plasma-atomic emission spectroscopy measurements confirmed metallodrug encapsulation and allowed us to determine the average amount of AP-1 trapped inside the cage. The X-ray structure of AP-1-encapsulated AFt was solved at 1.50 Å. Diffraction data revealed that an AP-1 fragment coordinates the side chain of a His residue. The biological activity of AP-1-loaded AFt was comparatively tested on a few representative cancer and non-cancer cell lines. Even though the presence of the cage reduces the overall cytotoxicity of AP-1, it improves its selectivity towards cancer cells.

Arsenoplatin-1 (AP-1) is an innovative dual-action anticancer agent that contains a platinum(ii) center coordinated to an arsenous acid moiety. We found that AP-1 spontaneously aggregates in aqueous solutions generating oligomeric species of increasing length. Afterward, we succeeded in solving the crystal structure of the adduct formed between the model protein lysozyme and an early AP-1 oligomer that turned out to be a trimer. Remarkably, this crystal structure traps an early stage of AP-1 aggregation offering detailed insight into the molecular process of the oligomer's growth.

Introduction: The COVID-19 pandemic poses an unprecedented challenge for the rapid discovery of drugs against this life-threatening disease. Owing to the peculiar features of the metal centers that are currently used in medicinal chemistry, metallodrugs might offer an excellent opportunity to achieve this goal., Areas Covered: Two main strategies for developing metal-based drugs against the SARS-CoV-2 are herein illustrated. Firstly, a few clinically approved metallodrugs could be evaluated in patients according to a 'drug repurposing' approach. To this respect, the gold drug auranofin seems a promising candidate, but some other clinically established metal compounds are worthy of a careful evaluation as well. On the other hand, libraries of inorganic compounds, featuring a large chemical diversity, should be screened to identify the most effective molecules. This second strategy might be assisted by a pathway-driven discovery approach arising from a preliminary knowledge of the mode of action, exploitable to inhibit the functional activities of the key viral proteins. Also, attention must be paid to selectivity and toxicity issues., Expert Opinion: The medicinal inorganic chemistry community may offer a valuable contribution against COVID-19. The screening of metallodrugs' libraries can expand the explored 'chemical space' and increase the chance of finding effective anti-COVID agents.

Gold and silver N-heterocyclic carbenes (NHCs) are emerging for therapeutic applications. Multiple techniques are here used to unveil the mechanistic details of the binding to different biosubstrates of bis(1-(anthracen-9-ylmethyl)-3-ethylimidazol-2-ylidene) silver chloride [Ag(EIA) 2 ]Cl and bis(1-(anthracen-9-ylmethyl)-3-ethylimidazol-2-ylidene) gold chloride [Au(EIA) 2 ]Cl. As the biosubstrates, we tested natural double-stranded DNA, synthetic RNA polynucleotides (single-poly(A), double-poly(A)poly(U) and triple-stranded poly(A)2poly(U)), DNA G-quadruplex structures (G4s), and bovine serum albumin (BSA) protein. Absorbance and fluorescence titrations, mass spectrometry together with melting and viscometry tests show significant differences in the binding features between silver and gold compounds. [Au(EIA) 2 ]Cl covalently binds BSA. It is here evidenced that the selectivity is high: low affinity and external binding for all polynucleotides and G4s are found. Conversely, in the case of [Ag(EIA) 2 ]Cl, the binding to BSA is weak and relies on electrostatic interactions. [Ag(EIA) 2 ]Cl strongly/selectively interacts only with double strands by a mechanism where intercalation plays the major role, but groove binding is also operative. The absence of an interaction with triplexes indicates the major role played by the geometrical constraints to drive the binding mode.

Electrospray ionization mass spectrometry (ESI MS) is a powerful investigative tool to analyze the reactions of metallodrugs with proteins and peptides and characterize the resulting adducts. Here, we have applied this type of approach to four experimental anticancer gold(III) compounds for which extensive biological and mechanistic data had previously been gathered, namely, Auoxo6, Au 2 phen, AuL12, and Aubipyc. These gold(III) compounds were reacted with two representative proteins, i.e., human serum albumin (HSA) and human carbonic anhydrase I (hCA I), and with the C-terminal dodecapeptide of thioredoxin reductase. ESI MS analysis allowed us to elucidate the nature of the resulting metal-protein adducts from which the main features of the occurring metallodrug-protein reactions can be inferred. In selected cases, MS data were integrated and supported by independent 1 HNMR and UV-Vis absorption measurements to gain an overall description of the occurring processes. From data analysis, it emerges that most of the investigated gold(III) complexes, endowed with an appreciable oxidizing character, undergo quite facile reduction to gold(I); the resulting gold(I) species tightly associate with the above proteins/peptides with a remarkable selectivity for free cysteine residues. In contrast, in the case of the less-oxidizing Aubipyc complex, the gold(III) oxidation state is conserved, and a gold(III) fragment still containing the original ligand is found to be associated with the target proteins. It is notable that the C-terminal dodecapeptide of thioredoxin reductase containing the characteristic -Gly-Cys-Sec-Gly metal-binding motif is able in all cases to trigger gold(III)-to-gold(I) reduction. Our investigation allowed us to identify in detail the nature of the gold fragments that ultimately bind the protein targets and determine the exact binding stoichiometry; some insight on the reaction kinetics was also gained. Notably, a few clear correlations could be established between the structure of the metal complexes and the nature of the resulting protein adducts. The mechanistic implications of these findings are analyzed and thoroughly discussed. Overall, the present results set the stage to better understand the real target biomolecules of these gold compounds and elucidate at the atomic level their interaction modes with proteins and peptides., (Copyright © 2020 Massai, Zoppi, Cirri, Pratesi and Messori.)

Native mass spectrometry is a potent technique to study and characterize biomacromolecules in their native state. Here, we have applied this method to explore the solution chemistry of human carbonic anhydrase I (hCA I) and its interactions with four different inhibitors, namely three sulfonamide inhibitors (AAZ, MZA, SLC-0111) and the dithiocarbamate derivative of morpholine (DTC). Through high-resolution ESI-Q-TOF measurements, the native state of hCA I and the binding of the above inhibitors were characterized in the molecular detail. Native mass spectrometry was also exploited to assess the direct competition in solution among the various inhibitors in relation to their affinity constants. Additional studies were conducted on the interaction of hCA I with the metallodrug auranofin, under various solution and instrumental conditions. Auranofin is a selective reagent for solvent-accessible free cysteine residues, and its reactivity was analyzed also in the presence of CA inhibitors. Overall, our investigation reveals that native mass spectrometry represents an excellent tool to characterize the solution behavior of carbonic anhydrase.

A group of triethylphosphine gold(I) and silver(I) complexes, structurally related to auranofin, were prepared and investigated as potential anticancer drug candidates. The antiproliferative properties of these metal compounds were assessed against two leukemia cell lines, i.e., CCRF-CEM and its multidrug-resistant counterpart, CEM/ADR5000. Interestingly, potent cytotoxic effects were disclosed for both series of compounds against leukemia cells, with IC 50 values generally falling in the low-micromolar range, the gold derivatives being on the whole more effective than the silver analogues. Some initial structure-function relationships were drawn. Subsequently, the ability of the study compounds to inhibit the three main catalytic activities of the proteasome was investigated. Different patterns of enzyme inhibition emerged for the various metal complexes. Notably, gold compounds were able to inhibit effectively both the trypsin-like and chymotrypsin-like proteasome activities, being less effective toward the caspase-like catalytic activity. In most cases, a significant selectivity of the study compounds toward the proteasome proteolytic activities was detected when compared to other proteases. The implications of the obtained results are discussed.

Au(PEt 3 )I (AF-I hereafter), the iodide analog of the FDA-approved drug auranofin (AF hereafter), is a promising anticancer agent that produces its pharmacological effects through interaction with non-genomic targets such as the thioredoxin reductase system. AF-I is endowed with a very favorable biochemical profile showing potent in vitro cytotoxic activity against several cancer types including ovarian and colorectal cancer. Remarkably, in a recent publication, some of us reported that AF-I induces an almost complete and rapid remission in an orthotopic in vivo mouse model of ovarian cancer. The cytotoxic potency does not bring about highly severe side effects, making AF-I very well-tolerated even for higher doses, even more so than the pharmacologically active ones. All these promising features led us to expand our studies on the mechanistic aspects underlying the antitumor activity of AF-I. We report here on an integrated experimental and theoretical study on the reactivity of AF-I, in comparison with auranofin, toward relevant aminoacidic residues or their molecular models. Results point out that the replacement of the thiosugar moiety with iodide significantly affects the overall reactivity toward the amino acid residues histidine, cysteine, methionine, and selenocysteine. Altogether, the obtained results contribute to shed light into the enhanced antitumoral activity of AF-I compared with AF., (Copyright © 2020 Tolbatov, Cirri, Marchetti, Marrone, Coletti, Re, La Mendola, Messori, Marzo, Gabbiani and Pratesi.)

Quite surprisingly, cisplatin and cis-[PtI 2 (NH 3 ) 2 ] were found to manifest significant differences in their reactions with the model protein lysozyme. We decided to explore whether these differences recur when reacting these two Pt compounds with other proteins. Notably, ESI-MS measurements carried out on cytochrome c nicely confirmed the reaction pattern observed for lysozyme. This prompted us to exploit a computational DFT approach to disclose the molecular basis of such behavior. We analyzed comparatively the reactions of cis-[PtCl 2 (NH 3 ) 2 ] and cis-[PtI 2 (NH 3 ) 2 ] with appropriate molecular models (Ls) of the sidechains of relevant aminoacids. We found that when Pt(II) complexes are reacted with sulfur ligands both quickly lose their halide ligands and then the resulting cis-[Pt(L) 2 (NH 3 ) 2 ] species loses ammonia upon reaction with a ligand excess. In the case of imidazole, again cis-[PtCl 2 (NH 3 ) 2 ] and cis-[PtI 2 (NH 3 ) 2 ] quickly lose their halide ligands but the resulting cis-[Pt(L) 2 (NH 3 ) 2 ] species does not lose ammonia by reaction with excess imidazole. These results imply that the two platinum complexes manifest a significantly different behavior in their reaction with representative small molecules in agreement with what observed in the case of model proteins. It follows that the protein itself must play a crucial role in triggering the peculiar reactivity of cis-[PtI 2 (NH 3 ) 2 ] and in governing the nature of the formed protein adducts. The probable reasons for the observed behavior are critically commented and discussed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The antiproliferative properties of a series of structurally-related gold(I) and silver(I) linear complexes inspired to the clinically established gold-based drug auranofin were investigated in A2780 ovarian cancer cells and in their auranofin (A2780/AF-R) and cisplatin (A2780/CDDP-R) resistant counterparts. In A2780 cells and in the cisplatin-resistant subline, gold-based analogues manifested a cytotoxicity profile comparable or superior to auranofin, while the silver-based analogues were less active; both gold and silver complexes overcame cisplatin resistance. Yet, a high degree of cross resistance toward gold analogues was noticed in A2780/AF-R cells. In the same cell line cross-resistance for silver analogues was also observed, though lower. All metal complexes were scrutinized for their ability to inhibit thioredoxin reductase (TrxR), the putative primary target for auranofin: overall, gold compounds were more potent TrxR inhibitors than the corresponding silver compounds, probably, as the consequence of the stronger binding of gold to the active site selenocysteine residue. These results highlight that the thiosugar ligand of auranofin is not essential for cytotoxicity while the nature of the metal center (gold/silver) plays a relevant role in its modulation. In addition, a rather clear correlation was found between cytotoxic potency of tested compounds and their ability to inhibit TrxR activity, being gold compounds more effective than silver analogues. However, the residual TrxR activity, measured in A2780 cells treated with the half-maximal inhibitory concentrations of various metal complexes, resulted far higher than expected. These results suggest that additional cytotoxic mechanisms must be operative. The implications of these results are discussed., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Studying metal-protein interactions is key for understanding the fate of metallodrugs in biological systems. When a metal complex is not emissive and too weakly bound for mass spectrometry analysis, however, it may become challenging to study such interactions. In this work a synthetic procedure was developed for the alkyne functionalization of a photolabile ruthenium polypyridyl complex, [Ru(tpy)(bpy)(Hmte)](PF 6 ) 2 , where tpy = 2,2':6',2''-terpyridine, bpy = 2,2'-bipyridine, and Hmte = 2-(methylthio)ethanol. In the functionalized complex [Ru(HCC-tpy)(bpy)(Hmte)](PF 6 ) 2 , where HCC-tpy = 4'-ethynyl-2,2':6',2''-terpyridine, the alkyne group can be used for bioorthogonal ligation to an azide-labeled fluorophore using copper-catalyzed "click" chemistry. We developed a gel-based click chemistry method to study the interaction between this ruthenium complex and bovine serum albumin (BSA). Our results demonstrate that visualization of the interaction between the metal complex and the protein is possible, even when this interaction is too weak to be studied by conventional means such as UV-vis spectroscopy or ESI mass spectrometry. In addition, the weak metal complex-protein interaction is controlled by visible light irradiation, i.e ., the complex and the protein do not interact in the dark, but they do interact via weak van der Waals interactions after light activation of the complex, which triggers photosubstitution of the Hmte ligand.

The clinically established gold drug Auranofin was reacted individually with a group of representative proteins, namely ubiquitin, ribonuclease A, carbonic anhydrase, haemoglobin and superoxide dismutase, and adduct formation was monitored in the various cases by ESI-MS analysis. We found that the reaction is highly selective for solvent exposed free cysteines that are modified through coordination of the AuPEt 3 + fragment. Indeed, ESI-Q-TOF MS spectra carried out on protein samples incubated with a three fold molar excess of Auranofin allowed direct detection of the native proteins bearing bound AuPEt 3 + fragments in the cases of carbonic anhydrase and haemoglobin. At variance, the two proteins that do not possess any free cysteine residue, i.e. ubiquitin and ribonuclease A, were unable to bind the gold fragment. In the case of superoxide dismutase, adduct formation is hindered by the scarce solvent accessibility of the free cysteine residue. These findings were further confirmed by a series of competition binding experiments with ebselen, a potent and selective cysteine-modifying reagent; we observed that pre-treatment with ebselen prevents the binding of the AuPEt 3 + fragment to both carbonic anhydrase and haemoglobin.

The interactions between the cytotoxic paddlewheel dirhodium complex [Rh2(μ-O2CCH3)4] and the model protein bovine pancreatic ribonuclease (RNase A) were investigated by high-resolution mass spectrometry and X-ray crystallography. The results indicate that [Rh2(μ-O2CCH3)4] extensively reacts with RNase A. The metal compound binds the protein via coordination of the imidazole ring of a His side chain to one of its axial sites, while the dirhodium center and the acetato ligands remain unmodified. Data provide valuable information for the design of artificial dirhodium-containing metalloenzymes.

An artificial alanine-based amino acid {(S)-2-amino-3-[4-propyl-3-(thiophen-2-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]propanoic acid, here named TioxAla}, bearing a substituted triazolyl-thione group on the side chain and able to bind RNA biomedical targets, was here chosen as a valuable scaffold for the synthesis of new platinum complexes with potential dual action owing to the concomitant presence of the metal centre and the amino acid moiety. Three new platinum complexes, obtained from the reaction of TioxAla with K 2 PtCl 4 , were characterized by mass spectrometry, nuclear magnetic resonance and UV-vis spectroscopy: one compound (Pt1, bis-{(S)-2-amino-3-[4-propyl-3-(thiophen-2-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]propanoate-O,S} platinum(II)) consisted of two amino acid units coordinating the Pt(II) ion; the other two, Pt2 [potassium dichloro-{(S)-2-amino-3-[4-propyl-3-(thiophen-2-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]propanoate (O,S)} platinum(II)] and Pt3 [potassium dichloro-{(S)-2-amino-3-[4-propyl-3-(thiophen-2-yl)-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-1-yl]propanoate (O,N)} platinum(II)], were isomers bearing one TioxAla unit, and two chlorides as Pt-ligands. Pt coordination involved preferentially the amino, carboxylic and thione functions of TioxAla. By preliminary antiproliferative assays, a moderate cytotoxic activity on cancer cells was observed only for Pt2 and Pt3, while no anticancer activity was found for both the chloride-free complex (Pt1) and TioxAla. This cytotoxicity, however lower than that of cisplatin, well correlated with the marked ability, here found only for Pt2 and Pt3 complexes, to bind DNA sequences either in random coil or in structured forms (duplex and G-quadruplex), as verified by spectroscopic and spectrometric analysis., (Copyright © 2019. Published by Elsevier Inc.)

Citrate-capped gold nanoparticles (AuNPs) were functionalized with three distinct antitumor gold(III) complexes, e.g., [Au(N,N)(OH) 2 ][PF 6 ], where (N,N)=2,2'-bipyridine; [Au(C,N)(AcO) 2 ], where (C,N)=deprotonated 6-(1,1-dimethylbenzyl)-pyridine; [Au(C,N,N)(OH)][PF 6 ], where (C,N,N)=deprotonated 6-(1,1-dimethylbenzyl)-2,2'-bipyridine, to assess the chance of tracking their subcellular distribution by atomic force microscopy (AFM), and surface enhanced Raman spectroscopy (SERS) techniques. An extensive physicochemical characterization of the formed conjugates was, thus, carried out by applying a variety of methods (density functional theory-DFT, UV/Vis spectrophotometry, AFM, Raman spectroscopy, and SERS). The resulting gold(III) complexes/AuNPs conjugates turned out to be pretty stable. Interestingly, they exhibited a dramatically increased resonance intensity in the Raman spectra induced by AuNPs. For testing the use of the functionalized AuNPs for biosensing, their distribution in the nuclear, cytosolic, and membrane cell fractions obtained from human lymphocytes was investigated by AFM and SERS. The conjugates were detected in the membrane and nuclear cell fractions but not in the cytosol. The AFM method confirmed that conjugates induced changes in the morphology and nanostructure of the membrane and nuclear fractions. The obtained results point out that the conjugates formed between AuNPs and gold(III) complexes may be used as a tool for tracking metallodrug distribution in the different cell fractions.

Three pseudohalide analogues of the established gold drug auranofin (AF hereafter), of general formula Au(PEt 3 )X, i.e. Au(PEt 3 )CN, Au(PEt 3 )SCN and Au(PEt 3 )N 3 (respectively denoted as AFCN, AFSCN and AFN 3 ), were prepared and characterized. The crystal structure was solved for Au(PEt 3 )SCN highlighting the classical linear geometry of the 2-coordinate gold(I) center. The solution behaviour of the compounds was then comparatively analysed through 31 PNMR providing evidence for an acceptable stability under physiological-like conditions. Afterward, the reaction of these gold compounds with bovine serum albumin (BSA) and consequent adduct formation was investigated by 31 PNMR. For all the studied gold compounds, the [Au(PEt 3 )] + moiety was identified as the reactive species in metal/protein adducts formation. The cytotoxic effects of the complexes were subsequently measured in comparison to AF against a representative colorectal cancer cell line and found to be still relevant and roughly similar in the three cases though far weaker than those of AF. These results show that the nature of the anionic ligand can modulate importantly the pharmacological action of the gold-triethylphosphine moiety, affecting the cytotoxic potency. These aspects may be further explored to improve the pharmacological profiles of this family of metal complexes.

The study of metal-based drugs represents an important branch of modern bioinorganic chemistry. The growing importance of this field is linked to the large success in medicine of a few metal based drugs, either in clinical use or still experimental. Moreover, these metal-based drugs are frequently used as reference compounds to assess comparatively the behavior of newly synthesized metallodrugs. For the convenience of researchers working in this area we report here a compilation of the relevant analytical and spectroscopic data of ten representative metallodrugs based on Platinum, Ruthenium, Gold and Mercury. The selected compounds, namely Cisplatin, Oxaliplatin, Carboplatin, Auranofin, Sodium Aurothiomalate, NAMI-A, KP1019, Thimerosal, Merbromin and Phenylmercury Acetate, were chosen owing to their importance in the field. We believe that this compilation may turn very helpful to researchers as these data are difficult to find and generally scattered over a large number of (old) publications.

A micro-electrochemical reaction cell was coupled to an electrospray mass spectrometer in order to track redox transformations for two representative medicinal gold compounds - i.e. [(2,3,4,6-tetra-O-acetyl-1-thio-β-D-glucopyranosato-S)(triethylphosphine)gold(I)] and [Au(bipy dmb -H)(OH)][PF 6 ] (where bipy dmb -H is deprotonated 6-(1,1-dimethylbenzyl)-2,2'-bipyridine), known as Auranofin and Aubipy c respectively - in parallel to square wave voltammetry (SWV) measurements. Irreversible oxidation of thio-glucose tetraacetate was the dominant reaction for the gold(I) compound Auranofin; oxidation was accompanied by hydrolysis leading to progressive deacetylation. Two main active forms were identified for this prodrug: the triethylphosphinegold(I) cation and a gold(I) thioglucose species, with a variable number of acetyl groups. For the gold(III) complex Aubipy c irreversible reduction of the gold(III) center was highlighted, accompanied by a ligand exchange process. The free gold(I) ion is proposed to be the final species that subsequently binds transport proteins in the bloodstream. Molecule specific mass spectrometry determinations provide complementary data to square wave voltammetry helping to understand the nature of the electrochemical conversions of complex or unstable compounds. Finally, it was possible to establish that oxidizing conditions during drug preparation and administration should be avoided in the case of Auranofin; conversely, reduction conditions typical for the blood or the cytosol environment are suitable to obtain the active gold(I) species from the gold(III) complex Aubipy c ., (Copyright © 2019 Elsevier Inc. All rights reserved.)

The medicinal gold(III) dithiocarbamato complex AuL 12 forms a stable adduct with bovine serum albumin. The crystal structure reveals that a single gold(I) center is bound to Cys34, with the dithiocarbamato ligand being released. To the best of our knowledge, this is the first structure for a gold adduct of serum albumin.

Malaria treatment and control have become increasingly difficult because of the spread of drug-resistant strains of Plasmodium falciparum and Plasmodium vivax . Thus, there is a continuous need to develop new combination therapies such as artemisinin-based combination therapies (ACTs) to contrast the emergence of resistant Plasmodium strains. Despite ACT has been recommended by the World Health Organization since 2001, its overall deployment in poor endemic areas is very slow, principally due to its high cost. In the malaria endemic areas, plant remedies are still widely used mostly without assurance of their efficacy and/or safety. A variety of widespread herbal drugs or natural products were already reported for their possible plasmodicidal activities, but the studies concerning their activity in combination with artemisinins are very scarce. The antimalarial activity of papaya is mostly anecdotal, and the present study is aimed at investigating the antiplasmodial activity of a decoction obtained by traditional recipe from the mature leaves of Carica papaya . The decoction was analyzed by HPLC-DAD-MS (high performance liquid chromatography coupled with diodoarray detector and mass spectrometry) showing the presence of caffeoyl derivatives and di- and triglycosides of flavonols. The extract was found to be active against P. falciparum 3D7 strains with a synergism in the presence of artemisinin. In vivo activity against the murine malaria model of Plasmodium berghei was disclosed both for the dried extract alone (250, 500, and 750 mg/kg/d) and for its combination with artesunate (250 mg/kg/d papaya plus 10 mg/kg/d artesunate). This combination displayed the greatest antimalarial activity in terms of reduction of parasitemia and prevention of recrudescence in animals recovered from the infection., Competing Interests: The authors declare that they have no conflict of interest., (Georg Thieme Verlag KG Stuttgart · New York.)

Competing Interests: Disclosure The authors report no conflicts of interest in this work.

Four-way junctions (4WJs) are supramolecular DNA assemblies comprising four interacting DNA strands that in biology are involved in DNA-damage repair. In this study, a new mononuclear platinum(II) complex 1 was prepared that is capable of driving the crystallization of the DNA oligomer 5'-d(CGTACG)-3' specifically into a 4WJ-like motif. In the crystal structure of the 1-CGTACG adduct, the distorted-square-planar platinum complex binds to the core of the 4WJ-like motif through π-π stacking and hydrogen bonding, without forming any platinum-nitrogen coordination bonds. Our observations suggest that the specific molecular properties of the metal complex are crucially responsible for triggering the selective assembly of this peculiar DNA superstructure., (© 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

NAMI-A ((ImH)[ trans -RuCl 4 (dmso-S)(Im)], Im = imidazole) and KP1019/1339 (KP1019 = (IndH)[ trans -RuCl 4 (Ind) 2 ], Ind = indazole; KP1339 = Na[ trans -RuCl 4 (Ind) 2 ]) are two structurally related ruthenium(III) coordination compounds that have attracted a lot of attention in the medicinal inorganic chemistry scientific community as promising anticancer drug candidates. This has led to a considerable amount of studies on their respective chemico-biological features and to the eventual admission of both to clinical trials. The encouraging pharmacological performances qualified KP1019 mainly as a cytotoxic agent for the treatment of platinum-resistant colorectal cancers, whereas the non-cytotoxic NAMI-A has gained the reputation of being a very effective antimetastatic drug. A critical and strictly comparative analysis of the studies conducted so far on NAMI-A and KP1019 allows us to define the state of the art of these experimental ruthenium drugs in terms of the respective pharmacological profiles and potential clinical applications, and to gain some insight into the inherent molecular mechanisms. Despite their evident structural relatedness, deeply distinct biological and pharmacological profiles do emerge. Overall, these two iconic ruthenium complexes form an exemplary and unique case in the field of medicinal inorganic chemistry.

Arsenoplatins are adducts of two chemically important anticancer drugs, cisplatin and arsenic trioxide, that have a Pt(II) bond to an As(III) hydroxide center. Screens of the NCI-60 human tumor cell lines reveal that arsenoplatin-1 (AP-1), [Pt(μ-NHC(CH 3 )O) 2 ClAs(OH) 2 ], the first representative of this novel class of anticancer agents, displays a superior activity profile relative to the parent drugs As 2 O 3 or cisplatin in a majority of cancer cell lines tested. These activity profiles are important because the success of arsenic trioxide in blood cancers (such as APL) has not been seen in solid tumors due to the rapid clearance of arsenous acid from the body. To understand the biological chemistry of these compounds, we evaluated interactions of AP-1 with the two important classes of biomolecules-proteins and DNA. The first structural studies of AP-1 bound to model proteins reveal that platinum(II) binds the Nε of His in a manner that preserves the Pt-As bond. We find that AP-1 readily enters cells and binds to DNA with an intact Pt-As bond (Pt:As ratio of 1). At longer incubation times, however, the Pt:As ratio in DNA samples increases, suggesting that the Pt-As bond breaks and releases the As(OH) 2 moiety. We conclude that arsenoplatin-1 has the potential to deliver both Pt and As species to a variety of hematological and solid cancers.

In recent years, a few successful attempts were made to repurpose the clinically approved antiarthritic gold drug, Auranofin ( AF ), as an anticancer agent. The present study shows that the iodido(triethylphosphine)gold(I) complex, ( Et 3 PAuI hereafter)-an AF analogue where the thiosugar ligand is simply replaced by one iodide ligand-manifests a solution chemistry resembling that of AF and exerts similar cytotoxic and proapoptotic effects on A2780 human ovarian cancer cells in vitro . However, when evaluated in a preclinical orthotopic model of ovarian cancer, Et 3 PAuI produces a far superior anticancer action than AF inducing a nearly complete tumor remission. The highly promising in vivo performances here documented for Et 3 PAuI warrant its further evaluation as a drug candidate for ovarian cancer treatment., Competing Interests: The authors declare no competing financial interest.

A series of palladium(II) (1-3) and platinum(II) chloride complexes (4 and 5) with 2,2':6',2″-terpyridine (terpy) derivatives substituted at the 4' position, was synthesized and fully characterized. Single crystal X-ray diffraction analysis of complexes 2, 3 and 5 showed tridentate coordination of the 4'-substituted terpyridine (terpy) ligands to the metal center. Moreover, in vitro cytotoxic activity of these complexes toward a panel of human cancer cell lines (lung cancer A549, colorectal cancer HCT116, ovarian cancer IGROV-1) and toward normal cell line HDF (dermal fibroblast) was determined by Trypan Blue exclusion assay. Overall, the tested compounds manifested a relevant cytotoxicity for the selected cancer cell lines with complex 4 also showing a modest cytotoxicity on the normal cell lines. To better understand the mode of action of these metal complexes, their reactivity with three model proteins, i.e. hen egg white lysozyme (HEWL), cytochrome c (cyt c) and ribonuclease A (RNase A) were comparatively investigated through ESI-MS analysis. The results highlighted a different behavior between the two series of complexes being platinum compounds more reactive toward RNase and cyt c than palladium compounds. Based on the obtained results, it is proposed that in presence of RNase A and cyt c, the platinum complexes undergo activation through release of labile ligands followed by binding to the protein. In contrast, palladium complexes revealed a far lower reactivity implying the likely occurrence of a different mechanism of action.

Stable five-coordinate Pt(II) complexes have been highlighted as a promising and original platform for the development of new cytotoxic drugs. Their interaction with proteins has been scarcely studied. Here, the reactivity of the five-coordinate Pt(II) compound [Pt(I)(Me) (dmphen)(olefin)] (Me = methyl, dmphen = 2,9-dimethyl-1,10-phenanthroline, olefin = dimethylfumarate) with the model proteins hen egg white lysozyme (HEWL) and bovine pancreatic ribonuclease (RNase A) has been investigated by X-ray crystallography and electrospray ionization mass spectrometry. The X-ray structures of the adducts of RNase A and HEWL with [Pt(I)(Me)(dmphen)(olefin)] are not of very high quality, but overall data indicate that, upon reaction with RNase A, the compound coordinates the side chain of His105 upon releasing the iodide ligand, but retains the pentacoordination. On the contrary, upon reaction with HEWL, the trigonal bi-pyramidal Pt geometry is lost, the iodide and the olefin ligands are released, and the metal center coordinates the side chain of His15 probably adopting a nearly square-planar geometry. This work underlines the importance of the combined use of crystallographic and mass spectrometry techniques to characterize, in detail, the protein⁻metallodrug recognition process. Our findings also suggest that five-coordinate Pt(II) complexes can act either retaining their uncommon structure or functioning as prodrugs, i.e., releasing square-planar platinum complexes as bioactive species.

The silver(I) N-heterocyclic carbene (NHC) complex bis(1-(anthracen-9-ylmethyl)-3-ethylimidazol-2-ylidene) silver chloride ([Ag(EIA) 2 ]Cl), bearing two anthracenyl fluorescent probes, has been synthesized and characterized. [Ag(EIA) 2 ]Cl is stable in organic solvents and under physiological conditions, and shows potent cytotoxic effects in vitro toward human SH-SY5Y neuroblastoma cells. The interactions of [Ag(EIA) 2 ]Cl with a few model biological targets have been studied as well as its ability to be internalized in cells. The in vitro anticancer activity is apparently related to the level of drug internalization. Notably, [Ag(EIA) 2 ]Cl does not react with a few model proteins, but is capable of binding the C-terminal dodecapeptide of thioredoxin reductase hTrxR(488-499) and to strongly inhibit the activity of this enzyme. Binding occurs through an unconventional process leading to covalent binding of one or two carbene ligands to the C-terminal dodecapeptide with concomitant release of the silver cation. To the best of our knowledge, this mode of interaction is reported here for the first time for Ag(NHC) 2 complexes., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The bis carbene gold(i) complex [Au(1-butyl-3-methyl-2-ylidene)2]PF6, ([Au(NHC)2]PF6 hereafter), holds remarkable interest as a perspective anticancer agent. The compound is stable under physiological like conditions: its original structure is retained even in the presence of excess glutathione (GSH). Previous studies revealed its high cytotoxicity in vitro that correlates with the impairment of crucial metabolic and enzymatic cellular processes (Magherini et al., Oncotarget, 2018, 9, 28042). Here, the interaction of [Au(NHC)2]PF6 with the human telomeric DNA G-quadruplex Tel23 has been investigated in solution by means of high resolution mass spectrometry. ESI MS experiments well document the formation of stable 1 : 1 adducts between the biscarbene gold complex - in its intact form - and the DNA G-quadruplex Tel23. Next, through independent biophysical methods, we show that [Au(NHC)2]PF6 binding does not significantly affect the G quadruplex melting temperature nor its conformation. The crystal structure for the [Au(NHC)2]+/Tel24 adduct was eventually determined by a joint X-ray diffraction and in silico simulation approach. Through the careful integration of solution and solid-state data, a quite clear picture emerges for the interaction of this gold complex with the Tel23 G-quadruplex.

Due to the so-called "antibiotic resistance crisis" new antibacterial agents are urgently sought to treat multidrug-resistant pathogens. A group of gold- or silver-based complexes, of general formula [M(PEt 3 )X] (with M=Au or Ag, and X=Cl, Br or I), alongside with three complexes bearing a positive or negative charge-[Au(PEt 3 ) 2 ]Cl, K[Au(CN) 2 ] and [Ag(PEt 3 ) 2 ]NO 3 -were prepared and comparatively tested with auranofin on a representative panel of pathogens including Gram-positive, Gram-negative and Candida strains. Interestingly, all the gold and silver complexes tested were active on Gram-positive strains, with the gold complexes having greater efficacy. The effects of the gold compounds were potentiated to a larger extent than silver compounds when tested in combination with a permeabilizing agent. A number of relevant structure-activity relationships emerged from the comparative analysis of the observed antibacterial profiles, shedding new light on the underlying molecular mechanisms of the action of these compounds., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The reactions of auranofin and three pseudohalide derivatives with bovine serum albumin were explored by ESI-Q-TOF mass spectrometry; a detailed molecular description of the resulting adducts is achieved revealing even subtle differences in reactivity within this series of gold(I) complexes. Our study shows that this kind of investigative approach, formerly applied to the interactions of metal-based drugs with small model proteins of MW 10-15 kDa, e.g., cytochrome c and lysozyme, may now be extended with success to far larger proteins such as serum albumin (MW 66 kDa).

The reaction of the antimetastatic ruthenium(iii) drug NAMI A with human H-chain ferritin (HuHf) was investigated through a variety of biophysical methods. We observed that the addition of HuHf to NAMI A solutions significantly increases the rate of spontaneous NAMI A hydrolysis suggesting the occurrence of a direct metallodrug-protein interaction. The resulting hydrolyzed Ru species binds the protein mostly forming a relatively tight 1 : 1 ruthenium/ferritin (subunit) adduct that was then separated and characterized. Notably, this adduct shows a characteristic CD spectrum in the visible region, which is diagnostic of the existence of at least one protein bound ruthenium center. The crystal structure of this NAMI A/HuHf adduct was subsequently solved at 1.58 Å resolution; clear evidence is given for the selective binding of a single Ru ion to His105 of each subunit with concomitant release of all other original Ru ligands in agreement with previous observations. We also noted that NAMI A produces a partial inhibition of HuHf ferroxidase activity. The implications of the above results are discussed.

An antiproliferative platinum(ii)-terpyridine complex bearing two piperidine substituents at positions 2 and 2' (compound 1, hereafter) interacts non-covalently with DNA and induces cell death through necrosis, i.e. a mode of action that is distinct from that exhibited by cisplatin (Suntharalingam, et al., Metallomics, 2013, 5, 514). Here, the interaction between this Pt compound and the model protein hen egg white lysozyme (HEWL) was studied by both electrospray ionization mass spectrometry (ESI MS) and X-ray crystallography. The ESI MS data collected after 24 h protein incubation with compound 1 at two different pH values offer evidence that the metal complex degrades upon reaction with HEWL, forming adducts with 1 : 1, 2 : 1 and 3 : 1 Pt/protein ratios. Two different X-ray structures of Pt-protein adducts, obtained by the reaction of HEWL with the Pt compound under different experimental conditions and incubation times, are then reported. An unexpected extensive platination of the protein is clearly observed: Pt containing fragments bind close to the NZ atom of Lys1 and OE1 atom of Glu7, NE2 atom of His15 and NH1 atom of Arg14, ND1 atom of His15, NZ atom of Lys96, NZ atom of Lys97 and ND1 atom of Asn93, NZ atom of Lys13 and the C-terminal carboxylate, and the N-terminal amine. An additional binding site was observed close to the NZ atom of Lys33. These results suggest that both N- and C-terminal tails, as well as Lys side chains, have to be considered as potential binding sites of Pt-containing drugs. The peculiar reactivity of compound 1 with biological macromolecules could play a role in its mode of action.

Au(NHC) and Au(NHC) 2 , i.e. a monocarbene gold(I) complex and the corresponding bis(carbene) complex, are two structurally related compounds, endowed with cytotoxic properties against several cancer cell lines. Herein, we explore the molecular and cellular mechanisms at the basis of their cytotoxicity in A2780 human ovarian cancer cells. Through a comparative proteomic analysis, we demonstrated that the number of modulated proteins is far larger in Au(NHC) 2 -treated than in Au(NHC)-treated A2780 cells. Both gold compounds mainly affected proteins belonging to the following functional classes: protein synthesis, metabolism, cytoskeleton and stress response and chaperones. Particularly, Au(NHC) 2 gave rise to an evident upregulation of several glycolytic enzymes. Moreover, only Au(NHC) 2 triggered a net impairment of respiration and a metabolic shift towards glycolysis, suggesting that mitochondria are relevant cellular targets. We also found that both carbenes, similarly to the gold(I) compound auranofin, caused a strong inhibition of the seleno-enzyme thioredoxin reductase (TrxR). In conclusion, we highlighted that coordination of two carbene ligands to the same gold(I) center greatly enhances the antiproliferative effects of the resulting compound in comparison to the monocarbene derivative. Moreover, TrxR inhibition and metabolic impairment seem to play a major role in the Au(NHC) 2 cytotoxicity. Overall, these antiproliferative effects were also confirmed on other two human ovarian cancer cell lines ( i.e. SKOV3 and IGROV1)., Competing Interests: CONFLICTS OF INTEREST The authors have no conflicts to disclose.

The triplatinum complex of the 2,4,6-Tris(2-pyrimidyl)-1,3,5-triazine ligand, Pt 3 TPymT hereafter, has been prepared and characterized for the first time. NMR studies point out that the three platinum(II) centers possess an identical coordination environment. The interactions of Pt 3 TPymT with DNA were explored in comparison to the free ligand. Specifically, fluorescence, mass spectrometry, viscometry and melting measurements were carried out. In contrast to expectations, the obtained data reveal that no intercalative binding takes place; we propose that binding of Pt 3 TPymT to DNA mainly occurs through external/groove binding., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Correction for 'Reactions of metallodrugs with proteins: selective binding of phosphane-based platinum(ii) dichlorides to horse heart cytochrome c probed by ESI MS coupled to enzymatic cleavage' by Carolin Mügge et al., Metallomics, 2011, 3, 987-990.

The tetranuclear Pt complex (PtL) 4 (where L 2- is the anion derived from para-isopropyl thiosemicarbazone) was first described in A.G. Quiroga et al., J. Med. Chem. 41, 1998, 1399-1408. (PtL) 4 manifests antiproliferative properties toward various cancer cell lines being a promising anticancer drug candidate. Yet, details of its reactivity with biomolecules have not been elucidated. To this end, we investigated the reactions of (PtL) 4 with a few model proteins, i.e. bovine pancreatic ribonuclease (RNase A), cytochrome c (Cyt c) and hen egg white lysozyme (Lysozyme), through electrospray ionization mass spectrometry and other biophysical methods. A rich reactivity of (PtL) 4 with the above-mentioned model proteins is observed, leading to the formation of numerous metallodrug-protein adducts. The tetranuclear complex breaks down and various fragments bind proteins up to high metal/protein ratios; this typically results into very complicated mass spectral patterns. However, some of the main mass peaks could be assigned in the case of the Lysozyme adduct. In addition, crystallographic data were obtained for the (PtL) 4 /Lysozyme and (PtL) 4 /RNase A adducts pointing at His side chains as the primary binding sites for monometallic Pt fragments. Notably, a few selected features of the interactions observed in the (PtL) 4 /protein adducts were reproduced by reacting (PtL) 4 with a small molecule, i.e. N-methylimidazole. In conclusion, the present study confirms the prodrug nature of the tetraplatinum complex, clarifies one possible pathway for its activation through cluster disassembly and allows initial identification of adducts formed with a representative protein., (Copyright © 2018 Elsevier Inc. All rights reserved.)

The general interest in anticancer metal-based drugs and some encouraging pharmacological results obtained at the beginning of the investigations on innovative Ru-based drugs triggered a lot of attention on NAMI-A and KP1019, the two Ru(III) coordination compounds that are the subject of this review. This great attention led to a considerable amount of scientific results and, more importantly, to their eventual admission into clinical trials. Both complexes share a relatively low systemic toxicity that allows reaching rather high dosages, comparable to those of carboplatin. Soon it became evident that NAMI-A and KP1019, in spite of their structural similarity, manifest very distinct chemical and biological properties. The pharmacological performances qualified KP1019 mainly as a cytotoxic drug for the treatment of platinum-resistant colorectal cancers, whereas NAMI-A gained the reputation of a potential anticancer drug with negligible effects on the primary tumor but a pronounced ability to affect metastases. We believe that a strictly comparative exam of NAMI-A and KP1019, based on the substantial body of studies accomplished since their discovery almost 30 years ago, might be an useful exercise, both for assessing the state of the art in terms of biological and clinical profiles, and of the inherent mechanisms, and for envisaging possible future developments in the light of past achievements.

Three new trans-ruthenium(ii) complexes coordinated to tetrapyridyl ligands, namely [Ru(bapbpy)(dmso)Cl]Cl ([2]Cl), [Ru(bapbpy)(Hmte) 2 ](PF 6 ) 2 ([3](PF 6 ) 2 ), and [Ru(biqbpy)(Hmte) 2 ](PF 6 ) 2 ([4](PF 6 ) 2 ), were prepared as analogues of [Ru(biqbpy)(dmso)Cl]Cl ([1]Cl), a recently described photoactivated chemotherapy agent. The new complexes were characterized, and their crystal structures showed the distorted coordination octahedron typical of this family of complexes. Their photoreactivity in solution was analyzed by spectrophotometry and mass spectrometry, which showed that the sulfur ligand was substituted upon blue light irradiation. The binding of the ruthenium complexes to a reference single-stranded oligonucleotide (s( 5' CTACGGTTTCAC 3' )) was explored both in the dark and under light irradiation by gel electrophoresis and high-resolution mass spectrometry. While adduct formation in the dark was negligible for the four complexes, light irradiation led to the formation of adducts with one or two ruthenium centers per oligonucleotide. The absence of interactions in the dark and the presence of complex-oligonucleotide adducts demonstrate that visible light controls the interaction of these ruthenium complexes with nucleic acids.

Background: Platinum-based drugs such as Cisplatin are commonly employed for cancer treatment. Despite an initial therapeutic response, Cisplatin treatment often results in the development of chemoresistance. To identify novel approaches to overcome Cisplatin resistance, we tested Cisplatin in combination with K + channel modulators on colorectal cancer (CRC) cells., Methods: The functional expression of Ca 2+ -activated (K Ca 3.1, also known as KCNN4) and voltage-dependent (K v 11.1, also known as KCNH2 or hERG1) K + channels was determined in two CRC cell lines (HCT-116 and HCT-8) by molecular and electrophysiological techniques. Cisplatin and several K + channel modulators were tested in vitro for their action on K + currents, cell vitality, apoptosis, cell cycle, proliferation, intracellular signalling and Platinum uptake. These effects were also analysed in a mouse model mimicking Cisplatin resistance., Results: Cisplatin-resistant CRC cells expressed higher levels of K Ca 3.1 and K v 11.1 channels, compared with Cisplatin-sensitive CRC cells. In resistant cells, K Ca 3.1 activators (SKA-31) and K v 11.1 inhibitors (E4031) had a synergistic action with Cisplatin in triggering apoptosis and inhibiting proliferation. The effect was maximal when K Ca 3.1 activation and K v 11.1 inhibition were combined. In fact, similar results were produced by Riluzole, which is able to both activate K Ca 3.1 and inhibit K v 11.1. Cisplatin uptake into resistant cells depended on K Ca 3.1 channel activity, as it was potentiated by K Ca 3.1 activators. K v 11.1 blockade led to increased K Ca 3.1 expression and thereby stimulated Cisplatin uptake. Finally, the combined administration of a K Ca 3.1 activator and a K v 11.1 inhibitor also overcame Cisplatin resistance in vivo., Conclusions: As Riluzole, an activator of K Ca 3.1 and inhibitor of K v 11.1 channels, is in clinical use, our results suggest that this compound may be useful in the clinic to improve Cisplatin efficacy and overcome Cisplatin resistance in CRC.

The anti-arthritic drug auranofin exerts also potent antitumour activity in in vitro and in vivo models, whose mechanisms are not yet well defined. From an auranofin-sensitive human ovarian cancer cell line A2780, a highly resistant (>20-fold) subline (A2780/AF-R) was developed and characterized. Marked reduction of gold accumulation occurred in auranofin-resistant A2780 cells. Also, moderately higher thioredoxin reductase activity in A2780/AF-R cells was observed while no changes in intracellular glutathione content occurred. Resistance to auranofin was associated with a low level of cross-resistance to some investigational gold compounds as well as to oxaliplatin and other anticancer drugs with different mode of action (i.e. melphalan, vinblastine, doxorubicin, etoposide, and paclitaxel). Reduced gold accumulation was associated to substantial gene expression changes in various influx (e.g. SLC22A1, SLC47A1, SLCO1B1 ) and efflux (e.g. ABCB1, ABCC2, ABCC3 ) transporters. The expression levels of selected proteins (i.e. SLC22A1, SLC47A1, P-gp) were also changed accordingly. These data provide evidence that multiple drug transporters may act as mediators of transport of auranofin and other gold compounds in cancer cells. Further investigation into the molecular mechanisms mediating transport of auranofin and new gold complexes in view of their potential clinical application in the treatment of cancer is warranted., Competing Interests: CONFLICTS OF INTEREST The authors declare no competing financial interests

Physicochemical methods have been used to investigate interactions occurring in solution between the dicarbene gold(I) complex [Au(9-methylcaffein-8-ylidene) 2 ]BF 4 (AuNHC) and a human telomeric DNA sequence, namely Tel23. Circular dichroism measurements allow identification of the conformational changes experienced by Tel23 upon interaction with AuNHC, and the respective binding stoichiometries and constants were determined. Computational studies provide a good link between previous crystallographic results of the same system and the present solution data, offering an exhaustive description of the inherent noncovalent metallodrug-DNA interactions. Remarkably, we found that a preformed AuNHC/Tel23 adduct is capable of producing strong and selective inhibition of the enzyme telomerase. The latter feature is mechanistically relevant and might account for the conspicuous in vitro anticancer properties of the investigated dicarbene gold(I) complex., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The solution behavior of auranofin, Et 3 PAuCl  and Et 3 PAuI, as well as their interactions with hen egg white lysozyme, single strand oligonucleotide, and ds-DNA were comparatively analyzed through NMR spectroscopy, ESI-MS, ethidium bromide displacement, DNA melting and viscometric tests. The cytotoxic effects toward representative colorectal cancer cell lines were found to be strong and similar in the three cases and a good correlation could be established between the cytotoxicity and the ability to inhibit thioredoxin reductase; remarkably, in vivo acute toxicity experiments for Et 3 PAuI confirmed that, similarly to auranofin, this drug is well tolerated in a murine model. Overall, a very similar profile emerges for Et 3 PAuI and Et 3 PAuCl, which retain the potent cytotoxic effects of auranofin while showing some peculiar features. These results demonstrate that the presence of the thiosugar moiety is not mandatory for the pharmacological action, suggesting that the tuning of some relevant chemical properties such as lipophilicity could be exploited to improve bioavailability, with no loss of the pharmacological effects.

The aim of this work is to identify the cisplatin binding sites on human H-chain ferritin. High-resolution X-ray crystallography reveals that cisplatin binds four distinct protein sites, that is, the side chains of His136 and Lys68, the side chain of His105, the side chain of Cys90 and the side chain of Cys102. These Pt binding sites are compared with those observed for the adduct that cisplatin forms upon encapsulation within horse spleen L-chain ferritin (87% identity with human L-chain ferritin).

A group of mixed-ligand Pt(II) complexes bearing acetylacetonate and sulphur ligands were recently developed in the University of Lecce as a new class of prospective anticancer agents that manifested promising pharma-cological properties in preliminary in vitro and in vivo tests. Though modelled on the basis of cisplatin, these Pt(II) complexes turned out to exhibit a profoundly distinct mode of action as they were found to act mainly on non-genomic targets rather than on DNA. Accordingly, we have explored here their reactions with two representative model proteins through an established ESI-MS procedure with the aim to describe their general interaction mechanism with protein targets. A pronounced reactivity with the tested proteins was indeed documented; the nature of the resulting metallodrug-protein interactions could be characterised in depth in the various cases. Preferential binding to protein targets compared to DNA is supported by independent ICP-OES measurements. The implications of these findings are discussed.