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Advances in inductively coupled plasma mass spectrometry and the methods used to prepare isotopically enriched standards, allow for the high accuracy measurement of metalloproteins by isotope dilution mass spectrometry. This technique has now reached a level of maturity whereby a step change in the accuracy, precision, and traceability of, in particular, clinical, and biomedical measurements is achievable. Current clinical measurements, which require low limits of detection in the presence of complex sample matrices, use indirect methods based on immunochemistry for the study of human disease. However, this approach suffers from poor traceability, requiring comparisons based on provision of matrix-based reference materials, used as analytical standards. This leads to difficulty when changes in the reference material are required, often resulting in a lack of interlaboratory and temporal comparability in clinical results and reference ranges. In this review, we focus on the most important metalloproteins for clinical studies, to illustrate how the attributes of chromatography coupled to inorganic mass spectrometry can be used for the direct measurement of metalloproteins such as hemoglobin, transferrin, and ceruloplasmin. By using this approach, we hope to demonstrate how isotope dilution analysis can be used as a reference method to improve traceability and underpin clinical, biomedical, and other biological measurements. [ABSTRACT FROM AUTHOR]

Interactions between proteins and metal ions and their complexes are important in many areas of the life sciences, including physiology, medicine, and toxicology. Despite the involvement of essential elements in all major processes necessary for sustaining life, metalloproteomes remain ill-defined. This is not only owing to the complexity of metalloproteomes, but also to the non-covalent character of the complexes that most essential metals form, which complicates analysis. Similar issues may also be encountered for some toxic metals. The review discusses recently developed approaches and current challenges for the study of interactions involving entire (sub-)proteomes with such labile metal ions. In the second part, transition metals from the fourth and fifth periods are examined, most of which are xenobiotic and also tend to form more stable and/or inert complexes. A large research area in this respect concerns metallodrug–protein interactions. Particular attention is paid to separation approaches, as these need to be adapted to the reactivity of the metal under consideration. [ABSTRACT FROM AUTHOR]

The role of the extracellular medium in influencing metal uptake into cells has not been described quantitatively. In a chemically-defined model system containing albumin, zinc influx into endothelial cells correlates with the extracellular free zinc concentration. Allosteric inhibition of zinc-binding to albumin by free fatty acids increased zinc flux. [ABSTRACT FROM AUTHOR]

Transition metal ions have a unique ability to organise and control the steric and electronic effects around a substrate in the active site of a catalyst. We consider half-sandwich Ru(II) (Noyori-type) and Os(II) sulfonyldiamine 16-electron active catalysts [Ru/Os(η6-p-cymene)(TsDPEN-H2)], where TsDPEN is N-tosyl-1,2-diphenylethylenediamine containing S,S or R,R chiral centres, which catalyse the highly efficient asymmetric transfer hydrogenation of aromatic ketones to chiral alcohols using formic acid as a hydride source. We discuss the recognition of the prochiral ketone acetophenone by the catalyst, the protonation of a ligand NH and transfer of hydride from formate to the metal, subsequent transfer of hydride to one enantiotopic face of the ketone, followed by proton transfer from metal-bound NH2, and regeneration of the catalyst. Our DFT calculations illustrate the role of the two chiral carbons on the N,N-chelated sulfonyldiamine ligand, the axial chirality of the π-bonded p-cymene arene, and the chirality of the metal centre. We discuss new features of the mechanism, including how a change in metal chirality of the hydride intermediate dramatically switches p-cymene coordination from η6 to η2. Moreover, the calculations suggest a step-wise mechanism involving substrate docking to the bound amine NH2 followed by hydride transfer prior to protonation of the O-atom of acetophenone and release of the enantio-pure alcohol. This implies that formation and stability of the M–H hydride intermediate is highly dependent on the presence of the protonated amine ligand. The Os(II) catalyst is more stable than the Ru(II) analogue, and these studies illustrate the subtle differences in mechanistic behaviour between these 4d6 and 5d6 second-row and third-row transition metal congeners in group 8 of the periodic table. [ABSTRACT FROM AUTHOR]

Most metallodrugs are prodrugs that can undergo ligand exchange and redox reactions in biological media. Here we have investigated the cellular stability of the anticancer complex [OsII[(η6‐p‐cymene)(RR/SS‐MePh‐DPEN)] [1] (MePh‐DPEN=tosyl‐diphenylethylenediamine) which catalyses the enantioselective reduction of pyruvate to lactate in cells. The introduction of a bromide tag at an unreactive site on a phenyl substituent of Ph‐DPEN allowed us to probe the fate of this ligand and Os in human cancer cells by a combination of X‐ray fluorescence (XRF) elemental mapping and inductively coupled plasma‐mass spectrometry (ICP‐MS). The BrPh‐DPEN ligand is readily displaced by reaction with endogenous thiols and translocated to the nucleus, whereas the Os fragment is exported from the cells. These data explain why the efficiency of catalysis is low, and suggests that it could be optimised by developing thiol resistant analogues. Moreover, this work also provides a new way for the delivery of ligands which are inactive when administered on their own. [ABSTRACT FROM AUTHOR]

Cyclometallated palladium(II) and platinum(II) pyrenyl-derived thiosemicarbazone (H2PrR) complexes of the type [M4(μ-S-PrR-κ3-C,N,S)4] (M = PdII, PtII; R = ethyl, cyclohexyl) have been synthesised in good yields and fully characterised. X-ray crystallography showed that the tetranuclear complex [Pt4(μ-S-PrCh-κ3-C,N,S)4](CH3)2COCHCl3 contains an eight-membered ring of alternating M–S atoms. The ethyl derivatives [M4(μ-S-PrEt-κ3-C,N,S)4] exhibit potent antiproliferative activity towards A2780 human ovarian cancer cells, with IC50 values of 1.27 μM (for M = PdII) and 0.37 μM (for M = PtII), the latter being an order of magnitude more potent than the anticancer drug cisplatin (IC50 1.20 μM). These promising complexes had low toxicity towards non-cancerous human MRC5 cells, which points towards an early indication of differential toxicity between cancer and normal cells. Experiments that investigated the effects of these tetranuclear complexes on the cell cycle, integrity of the cell membrane, and induction of apoptosis, suggested that their mechanism of action of does not involve DNA targeting, unlike cisplatin, and therefore could be promising for combatting cisplatin resistance. [ABSTRACT FROM AUTHOR]

Functionalised triazole aldehydes are used in the highly selective self-assembly of water-compatible, optically pure, low symmetry Fe(II)- and Zn(II)-based metallohelices. Sub-micromolar antiproliferative activity is observed against various cancerous cell lines, accompanied by excellent selectivity versus non-cancerous cells and potential for synergistic combinatorial therapy with cisplatin. [ABSTRACT FROM AUTHOR]

New palladium complexes with thiosemicarbazonate ligands derived from pyrene exhibit potent antiproliferative activity against A2780 and cisplatin-resistant A2780Cis human ovarian cancer cells, which is dependent on substituent groups of the thiosemicarbazone ligands. Cellular accumulation and distribution studies confirmed that palladium enters the cell nucleus. DNA and topoisomerase IB studies show that one complex is a potent TopIB inhibitor, with selectivity for cancer versus normal cells. [ABSTRACT FROM AUTHOR]

A series of neutral pseudo-octahedral RuII sulfonamidoethylenediamine complexes [(η6-p-cym)Ru(N,N′)Cl] where N,N′ is N-(2-(R1,R2-amino)ethyl)-4-toluenesulfonamide (TsEn(R1,R2)) R1,R2 = Me,H (1); Me,Me (2); Et,H (3); benzyl,H (Bz, 4); 4-fluorobenzyl,H (4-F-Bz, 5) or naphthalen-2-ylmethyl,H (Naph, 6), were synthesised and characterised including the X-ray crystal structure of 3. These complexes catalyse the reduction of NAD+ regioselectively to 1,4-NADH by using formate as the hydride source. The catalytic efficiency depends markedly on the steric and electronic effects of the N-substitutent, with turnover frequencies (TOFs) increasing in the order: 1 ＜ 2 ＜ 3, 6 ＜ 4, 5, achieving a TOF of 7.7 h−1 for 4 with a 95% yield of 1,4-NADH. The reduction rate was highest between pH* (deuterated solvent) 6 and 7.5 and improved with an increase in formate concentration (TOF of 18.8 h−1, 140 mM formate). The calculations suggested initial substitution of an aqua ligand by formate, followed by hydride transfer to RuII and then to NAD+, and indicated specific interactions between the aqua complex and both NAD+ and NADH, the former allowing a preorganisation involving interaction between the aqua ligand, formate anion and the pyridine ring of NAD+. The complexes exhibited antiproliferative activity towards A2780 human ovarian cancer cells with IC50 values ranging from 1 to 31 μM, the most potent complex, [(η6-p-cym)Ru(TsEn(Bz,H))Cl] (4, IC50 = 1.0 ± 0.1 μM), having a potency similar to the anticancer drug cisplatin. Co-administration with sodium formate (2 mM), increased the potency of all complexes towards A2780 cells by 20–36%, with the greatest effect seen for complex 6. [ABSTRACT FROM AUTHOR]

Asymmetric transfer hydrogenation (ATH) is an important process in organic synthesis for which the Noyori-type RuII catalysts [(arene)Ru(Tsdiamine)] are now well established and widely used. We now demonstrate for the first time the catalytic activity of the osmium analogues. X-ray crystal structures of the 16-electron OsII catalysts are almost identical to those of RuII. Intriguingly the precursor complex was isolated as a dichlorido complex with a monodentate amine ligand. The OsII catalysts are readily synthesised (within 1 h) and exhibit excellent enantioselectivity in ATH reactions of ketones. [ABSTRACT FROM AUTHOR]

The development of catalytic metallodrugs is an emerging field that may offer new approaches to cancer chemotherapeutic design. By exploiting the unique properties of transition metal complexes, in‐cell catalysis can be applied to modulate the cellular redox balance as part of a multi‐targeting mechanism of action. We describe the synthesis and characterization of six coordinatively unsaturated iridium(III) diamine catalysts that are stable at physiological pH in aqueous solution. Reduction of the colorimetric substrate 2,6‐dichlorophenolindophenol by transfer hydrogenation under biologically compatible conditions achieved turnover frequencies up to 63 ± 2 h−1 and demonstrated that the source of hydride (sodium formate) is the limiting reagent, despite being in a 1000‐fold excess of the catalyst. The catalyst showed low in vivo acute toxicity in zebrafish embryos and modest in vitro potency towards cancer cells. When administered alone, the catalyst generated oxidative stress in cells (an effect that was conserved in vivo), but co‐treatment with a nontoxic dose of sodium formate negated this effect. Co‐treatment with sodium formate significantly enhanced catalyst potency in cancer cells (A2780 ovarian and MCF7 breast cancer cells) and drug‐resistant cells (A2780cis and MCF7‐TAMR1) but not in non‐tumorigenic cells (MRC5), demonstrating that a redox‐targeting mechanism may generate selectivity for cancer cells. [ABSTRACT FROM AUTHOR]

Simple Summary: Ovarian cancer is the fifth most common cancer in the developing world, with many front-line treatments combining paclitaxel with platinum-based anticancer agents cisplatin/carboplatin. However, increased incidence of platinum resistance demands the development of new chemotherapeutic agents. The aim of our study was to explore a new family of organoruthenium(II) pyrithione complexes for their efficacy towards platinum-resistant ovarian cancer cells. We confirmed that this new class of compounds remain highly potent towards platinum-insensitive cells and appear to work by a mechanism that is not common to platinum agents. Drug resistance to existing anticancer agents is a growing clinical concern, with many first line treatments showing poor efficacy in treatment plans of some cancers. Resistance to platinum agents, such as cisplatin, is particularly prevalent in the treatment of ovarian cancer, one of the most common cancers amongst women in the developing world. Therefore, there is an urgent need to develop next generation of anticancer agents which can overcome resistance to existing therapies. We report a new series of organoruthenium(II) complexes bearing structurally modified pyrithione ligands with extended aromatic scaffold, which overcome platinum and adriamycin resistance in human ovarian cancer cells. The mechanism of action of such complexes appears to be unique from that of cisplatin, involving G1 cell cycle arrest without generation of cellular ROS, as is typically associated with similar ruthenium complexes. The complexes inhibit the enzyme thioredoxin reductase (TrxR) in a model system and reduce cell motility towards wound healing. Importantly, this work highlights further development in our understanding of the multi-targeting mechanism of action exhibited by transition metal complexes. [ABSTRACT FROM AUTHOR]

Frontispiece: Tracking Reactions of Asymmetric Organo-Osmium Transfer Hydrogenation Catalysts in Cancer Cells Anticancer catalysts, bioorganometallic chemistry, X-ray fluorescence, organo-osmium complexes, transfer hydrogenation Keywords: anticancer catalysts; bioorganometallic chemistry; X-ray fluorescence; organo-osmium complexes; transfer hydrogenation EN anticancer catalysts bioorganometallic chemistry X-ray fluorescence organo-osmium complexes transfer hydrogenation 1 1 1 03/10/21 20210315 NES 210315 B Anticancer Complexes b In their Research Article on page 6462, Paul D. Quinn, Carlos Sanchez-Cano, Peter J. Sadler et al. track reactions of asymmetric organo-osmium transfer hydrogenation catalysts in cancer cells. [Extracted from the article]

After nearly 20 years of research on the use of ruthenium in the fight against cancer, only two Ru(III) coordination complexes have advanced to clinical trials. During this time, the field has produced excellent candidate drugs with outstanding in vivo and in vitro activity; however, we have yet to find a ruthenium complex that would be a viable alternative to platinum drugs currently used in the clinic. We aimed to explore what we have learned from the most prominent complexes in the area, and to challenge new concepts in chemical design. Particularly relevant are studies involving NKP1339, NAMI-A, RM175, and RAPTA-C, which have paved the way for current research. We explored the development of the ruthenium anticancer field considering that the mechanism of action of complexes no longer focuses solely on DNA interactions, but explores a diverse range of cellular targets involving multiple chemical strategies. [ABSTRACT FROM AUTHOR]

Objectives: Assessment of Wilson disease is complicated, with neither ceruloplasmin, nor serum or urine copper, being reliable. Two new indices, accurate non-ceruloplasmin copper (ANCC) and relative ANCC were developed and applied to a cohort of 71 patients, as part of a Wilson Disease Registry Study., Methods: Elemental copper-protein speciation was developed for holo-ceruloplasmin quantitation using strong anion exchange chromatography coupled to triple quadrupole inductively coupled plasma mass spectrometry. The serum proteins were separated using gradient elution and measured at m / z 63 ( 63 Cu + ) and 48 ( 32 S 16 O + ) using oxygen reaction mode and Cu-EDTA as calibration standard. The ANCC was calculated by subtraction of the ceruloplasmin bound copper from the total serum copper and the RelANCC was the percentage of total copper present as the ANCC., Results: The accuracy of the holo-ceruloplasmin measurement was established using two certified reference materials, giving a mean recovery of 94.2 %. Regression analysis between the sum of the copper containing species and total copper concentration in the patient samples was acceptable (slope=0.964, intercept=0, r=0.987) and a difference plot, gave a mean difference for copper of 0.38 μmol/L. Intra-day precision for holo-ceruloplasmin at serum copper concentrations of 0.48 and 3.20 μmol/L were 5.2 and 5.6 % CV and the intermediate precision at concentrations of 0.80 and 5.99 μmol/L were 6.4 and 6.4 % CV, respectively. The limit of detection (LOD) and lower limit of quantification (LLOQ) for holo-ceruloplasmin were 0.08 and 0.27 μmol/L as copper, respectively., Conclusions: ANCC and Relative ANCC are important new diagnostic and monitoring biomarker indices for Wilson disease (WD)., (© 2024 Walter de Gruyter GmbH, Berlin/Boston.)

Cyclometallated palladium(ii) and platinum(ii) pyrenyl-derived thiosemicarbazone (H2PrR) complexes of the type [M4(μ-S-PrR-κ3-C,N,S)4] (M = PdII, PtII; R = ethyl, cyclohexyl) have been synthesised in good yields and fully characterised. X-ray crystallography showed that the tetranuclear complex [Pt4(μ-S-PrCh-κ3-C,N,S)4](CH3)2COCHCl3 contains an eight-membered ring of alternating M-S atoms. The ethyl derivatives [M4(μ-S-PrEt-κ3-C,N,S)4] exhibit potent antiproliferative activity towards A2780 human ovarian cancer cells, with IC50 values of 1.27 μM (for M = PdII) and 0.37 μM (for M = PtII), the latter being an order of magnitude more potent than the anticancer drug cisplatin (IC50 1.20 μM). These promising complexes had low toxicity towards non-cancerous human MRC5 cells, which points towards an early indication of differential toxicity between cancer and normal cells. Experiments that investigated the effects of these tetranuclear complexes on the cell cycle, integrity of the cell membrane, and induction of apoptosis, suggested that their mechanism of action of does not involve DNA targeting, unlike cisplatin, and therefore could be promising for combatting cisplatin resistance.

New palladium complexes with thiosemicarbazonate ligands derived from pyrene exhibit potent antiproliferative activity against A2780 and cisplatin-resistant A2780Cis human ovarian cancer cells, which is dependent on substituent groups of the thiosemicarbazone ligands. Cellular accumulation and distribution studies confirmed that palladium enters the cell nucleus. DNA and topoisomerase IB studies show that one complex is a potent TopIB inhibitor, with selectivity for cancer versus normal cells.

In mammalian blood plasma, serum albumin acts as a transport protein for free fatty acids, other lipids and hydrophobic molecules including neurodegenerative peptides, and essential metal ions such as zinc to allow their systemic distribution. Importantly, binding of these chemically extremely diverse entities is not independent, but linked allosterically. One particularly intriguing allosteric link exists between free fatty acid and zinc binding. Albumin thus mediates crosstalk between energy status/metabolism and organismal zinc handling. In recognition of the fact that even small changes in extracellular zinc concentration and speciation modulate the function of many cell types, the albumin-mediated impact of free fatty acid concentration on zinc distribution may be significant for both normal physiological processes including energy metabolism, insulin activity, heparin neutralisation, blood coagulation, and zinc signalling, and a range of disease states, including metabolic syndrome, cardiovascular disease, myocardial ischemia, diabetes, and thrombosis., (Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.)

Myocardial ischemia is difficult to diagnose effectively with still few well-defined biochemical markers for identification in advance, or in the absence of myocardial necrosis. "Ischemia-modified albumin" (IMA), a form of albumin displaying reduced cobalt-binding affinity, is significantly elevated in ischemic patients, and the albumin cobalt-binding (ACB) assay can measure its level indirectly. Elucidating the molecular mechanism underlying the identity of IMA and the ACB assay hinges on understanding metal-binding properties of albumin. Albumin binds most metal ions and harbours four primary metal binding sites: site A, site B, the N-terminal site (NTS), and the free thiol at Cys34. Previous efforts to clarify the identity of IMA and the causes for its reduced cobalt-binding capacity were focused on the NTS site, but the degree of N-terminal modification could not be correlated to the presence of ischemia. More recent work suggested that Co 2+ ions as used in the ACB assay bind preferentially to site B, then to site A, and finally to the NTS. This insight paved the way for a new consistent molecular basis of the ACB assay: albumin is also the main plasma carrier for free fatty acids (FFAs), and binding of a fatty acid to the high-affinity site FA2 results in conformational changes in albumin which prevent metal binding at site A and partially at site B. Thus, this review advances the hypothesis that high IMA levels in myocardial ischemia and many other conditions originate from high plasma FFA levels hampering the binding of Co 2+ to sites A and/or B. This is supported by biophysical studies and the co-association of a range of pathological conditions with positive ACB assays and high plasma FFA levels., (Copyright © 2018. Published by Elsevier Ltd.)

A series of neutral pseudo-octahedral RuII sulfonamidoethylenediamine complexes [(η6-p-cym)Ru(N,N')Cl] where N,N' is N-(2-(R1,R2-amino)ethyl)-4-toluenesulfonamide (TsEn(R1,R2)) R1,R2 = Me,H (1); Me,Me (2); Et,H (3); benzyl,H (Bz, 4); 4-fluorobenzyl,H (4-F-Bz, 5) or naphthalen-2-ylmethyl,H (Naph, 6), were synthesised and characterised including the X-ray crystal structure of 3. These complexes catalyse the reduction of NAD+ regioselectively to 1,4-NADH by using formate as the hydride source. The catalytic efficiency depends markedly on the steric and electronic effects of the N-substitutent, with turnover frequencies (TOFs) increasing in the order: 1 < 2 < 3, 6 < 4, 5, achieving a TOF of 7.7 h-1 for 4 with a 95% yield of 1,4-NADH. The reduction rate was highest between pH* (deuterated solvent) 6 and 7.5 and improved with an increase in formate concentration (TOF of 18.8 h-1, 140 mM formate). The calculations suggested initial substitution of an aqua ligand by formate, followed by hydride transfer to RuII and then to NAD+, and indicated specific interactions between the aqua complex and both NAD+ and NADH, the former allowing a preorganisation involving interaction between the aqua ligand, formate anion and the pyridine ring of NAD+. The complexes exhibited antiproliferative activity towards A2780 human ovarian cancer cells with IC50 values ranging from 1 to 31 μM, the most potent complex, [(η6-p-cym)Ru(TsEn(Bz,H))Cl] (4, IC50 = 1.0 ± 0.1 μM), having a potency similar to the anticancer drug cisplatin. Co-administration with sodium formate (2 mM), increased the potency of all complexes towards A2780 cells by 20-36%, with the greatest effect seen for complex 6.

We report the synthesis and characterization of four neutral organometallic tethered complexes, [Ru(η 6 -Ph(CH 2 ) 3 -ethylenediamine- N -R)Cl], where R = methanesulfonyl (Ms, 1 ), toluenesulfonyl (Ts, 2 ), 4-trifluoromethylbenzenesulfonyl (Tf, 3 ), and 4-nitrobenzenesulfonyl (Nb, 4 ), including their X-ray crystal structures. These complexes exhibit moderate antiproliferative activity toward human ovarian, lung, hepatocellular, and breast cancer cell lines. Complex 2 in particular exhibits a low cross-resistance with cisplatin. The complexes show potent catalytic activity in the transfer hydrogenation of NAD + to NADH with formate as hydride donor in aqueous solution (310 K, pH 7). Substituents on the chelated ligand decreased the turnover frequency in the order Nb > Tf > Ts > Ms. An enhancement of antiproliferative activity (up to 22%) was observed on coadministration with nontoxic concentrations of sodium formate (0.5-2 mM). Complex 2 binds to nucleobase guanine (9-EtG), but DNA appears not to be the target, as little binding to calf thymus DNA or bacterial plasmid DNA was observed. In addition, complex 2 reacts rapidly with glutathione (GSH), which might hamper transfer hydrogenation reactions in cells. Complex 2 induced a dose-dependent G 1 cell cycle arrest after 24 h exposure in A2780 human ovarian cancer cells while promoting an increase in reactive oxygen species (ROS), which is likely to contribute to its antiproliferative activity., Competing Interests: The authors declare no competing financial interest.