Breast cancer is the most common malignant neoplasm among women and exhibits high molecular heterogeneity, which directly influences therapeutic response and clinical outcomes. Despite advances in targeted therapies and immunotherapies, tumor recurrence, resistance to conventional treatments, and metastatic potential reinforce the need for more selective and effective pharmacological strategies. In this context, metal complexes, particularly ruthenium(II) derivatives, have attracted considerable attention due to their antitumor profile, greater selectivity, and lower systemic toxicity. Therefore, in the present study, the antineoplastic activity of the RuMTZ complex (2-mercaptothiazoline-di-1,2-bis(diphenylphosphine)ethane-ruthenium(II)) was evaluated in three breast cancer cell lines (MDA-MB-231, MDA-MB-468 and MCF7) and in one non-tumor breast cell line (MCF10A). RuMTZ exhibited greater cytotoxicity against human MDA-MB-468 cells, as demonstrated by cell viability (IC50 = 1.8 µM) and clonogenic (IC50 = 0.08 µM) assays, associated with higher selectivity indexes (3.89 and 3.75, respectively). Further studies demonstrated that RuMTZ inhibited cell migration by up to 62.76% and induced cell-cycle arrest in the G0/G1 phase, accompanied by a reduction in the G2/M population. Furthermore, the ruthenium complex induced apoptotic cell death, as observed by flow cytometry and increased levels of cleaved caspase-3 by Western blot. The genotoxic effect of RuMTZ was evidenced by the comet assay and increased γH2AX expression levels. Taken together, these findings demonstrate that RuMTZ exhibits promising antineoplastic activity against breast cancer cells, associated with cell-cycle arrest, induction of DNA damage, and apoptosis.

O2-tolerance is a desirable property for [FeFe] hydrogenases, which are highly efficient H2-producing catalysts. While most such enzymes are highly sensitive to aerobic environments, a small number of explored representatives exhibit exceptional stability and even H2-producing activity under oxygenic conditions. However, the genetic signatures of the O2-tolerance in this class of enzymes remain largely unknown. To address this knowledge gap, we explored a close homologue of a well-characterized O2-tolerant [FeFe] hydrogenase from Clostridium beijerinckii (CbHydA1)-a hydrogenase from Terrisporobacter glycolicus (TgHydA1). Our investigation indeed confirms that TgHydA1 can transition to the O2-stable Hinact state, a hallmark of O2 tolerance. The surprising outcome is that despite the high amino acid similarity, TgHydA1 shows a substantially higher propensity to remain in the Hinact state than CbHydA1. Using protein film electrochemical experiments, we demonstrate that the root of this behavior lies in roughly tenfold slower reactivation rates than those of CbHydA1 at any applied potential. This degree and direction of variation in reactivation kinetics have not been observed before for any other O2-tolerant [FeFe] hydrogenases or their variants to date, uncovering a yet-to-be-explored facet of reactivity alteration available to these enzymes. Overall, the results presented here highlight the importance of a holistic analysis of [FeFe] hydrogenase sequences in the context of their interaction with O2 that encompasses the protein environment and properties of the auxiliary metallocofactors.

Copper is an essential yet potentially toxic biological trace element, whose functions in cells arise from its unique redox and coordination chemistry. The same chemical properties that make copper indispensable for a variety of fundamental biological processes, including respiration and antioxidant defense, also render it highly toxic when intracellular concentrations exceed homeostatic levels. Recently, a copper-dependent form of regulated cell death (RCD) termed cuproptosis has been identified, in which excess copper triggers cytotoxicity by directly binding the metabolic machinery of mitochondria to induce proteotoxic stress. Hallmark features of cuproptosis include the high-affinity coordination of copper with lipoylated proteins and the destabilization of iron-sulfur (Fe-S) cluster enzymes within the mitochondrial matrix, which together trigger metabolic dysfunction and protein aggregation that ultimately lead to cell death. Cuproptosis thus represents the first RCD pathway whose execution depends directly on metal-protein coordination chemistry. Emerging evidence indicates that cuproptosis may contribute to the pathogenesis of a variety of human diseases including cancer, neurodegeneration, and genetic disorders of copper metabolism. A precise mechanistic understanding of this form of RCD therefore has the potential to reveal new opportunities for therapeutic intervention. Here, we examine the bioinorganic basis of cuproptosis, its intersections with cellular copper handling systems, its role in disease processes, and the potential therapeutic strategies that aim to exploit this pathway for clinical benefit.

Reported here is an investigation of the redox behavior of myoglobin (Mb) in the presence of several bioactive compounds with biomedical relevance. These include the well-known Pt(II) drug, cisplatin, oxoplatin (a Pt(IV) compound representative for a newer-generation drugs based on platinum), capric acid, fenbufen, plumbagin and fisetin. These molecules were selected based on their structural diversity and documented biological effects, such as anti-inflammatory, chemotherapeutic, or antioxidant properties. The study aimed to evaluate how these compounds affect the structural and redox properties of Mb, particularly in terms of their capacity to bind to the protein and modulate its oxidation state. Spectroscopic and computational methods (UV-Vis absorption, fluorescence, NMR, molecular docking and molecular dynamics) were used to monitor binding and modifications of the redox state of the Mb in reactions such as autoxidation, nitrite-induced autoxidation, and peroxide-induced damage. These experiments are designed to parallel previous findings with similar experiments on hemoglobin with small molecules of biomedical/therapeutic relevance. While some compounds induced minimal or no spectral changes - suggesting limited interaction or redox impact, others displayed distinct redox effects, with plumbagin promoting oxidation while fisetin exerted a stabilizing, protective influence on the oxygenated form of myoglobin. These findings suggest that plumbagin may act as pro-oxidant by promoting myoglobin oxidation, whereas fisetin interacts with Mb in a manner that stabilizes the oxygenated form and mitigates oxidative conversion. The observed variability highlights the complex nature of small molecule-protein interactions and underlines the importance of assessing individual compound behavior in biochemical systems.

Chrysin, structurally one of the simplest flavonoids, shows a broad spectrum of biological activities, particularly its anticancer potential. Additionally, it has the possibility of coordination to metal ions as a bidentate chelate ligand, forming highly stable metal complexes. This synergism of metal ions and Chrysin led to a significant improvement in its diverse biological activities. Chrysin (HL1) and its derivatives (methoxy (HL2), benzyloxy (HL3), acetylated (HL4), and silylated (HL5)) were coordinated as OO-bidentate ligands to the rhenium(V) ion, and all five complexes crystallized in the form of monocrystals. The stability studies in PBS and human blood plasma solution were performed for those compounds, indicating that all complexes underwent precipitation in PBS, whereas no precipitation was observed in plasma. Moreover, the spectral profiles recorded in plasma indicate that plasma components exert a significant stabilizing effect on the rhenium complexes. The antiproliferative activity of complexes 1-5 was evaluated against the human ovarian carcinoma (A2780), colorectal carcinoma (HCT116), and the non-malignant HEK293 cell line. No direct relationship could be established between the complex precipitation in plasma and its cytotoxic activity. Complex 3 displayed pronounced spectral modifications in plasma while remaining essentially inactive in all cell lines tested, whereas 1 exhibited comparatively limited spectral changes despite being among the most active compounds of the series. The most active complexes 5, 1, and 2 displayed significant selectivity, with lower cytotoxicity toward non-tumorigenic HEK293 cells than A2780 and HCT116 cancer cells.

The enzymatic degradation of polyethylene (PE) by oxidative enzymes remains poorly understood at the molecular level, limiting the development of effective biotechnological strategies for plastic valorization. Here, we investigate the molecular basis of PE oxidation by the laccase-like multicopper oxidase LMCO2 from Rhodococcus opacus R7 with combined DFT and molecular docking calculations. LMCO2 is a particularly relevant model system because it has been experimentally shown to oxidatively modify low-density polyethylene without the need for mediators, despite its relatively low redox potential. DFT calculations indicate that direct oxidation of aliphatic C-H bonds in pristine PE is energetically prohibitive, and that hydroxylated defects do not significantly facilitate substrate activation. In contrast, oxidation at carbon atoms adjacent to carbonyl groups is associated with substantially lower barriers, owing to stabilization of the resulting radicals through conjugation and keto-enol tautomerism. Alternative pathways involving alkoxyl radicals and β-scission were also examined and found to be energetically unfavorable. Molecular docking calculations complement this picture by showing that both pristine and pre-oxidized PE segments can access the main cavity adjacent to the T1 copper site, although binding is weak and largely non-specific. Taken together, these results support a mechanism in which LMCO2 selectively acts on pre-oxidized, carbonyl-containing regions of polyethylene, promoting further radical chemistry that may ultimately lead to chain scission and the formation of low-molecular-weight oxygenated products.

The study evaluated the current patterns of guideline-recommended clinical use, real-world utilization trends, and translational development of platinum-based (Pt-based) drugs through a comparative analysis of national and international pharmacotherapeutic guidelines, national drug utilization data, clinical trials, and emerging research directions. Cisplatin, carboplatin and oxaliplatin continue to play central roles across multiple malignancies and remain widely incorporated into recommended treatment protocols. Across all five guideline sources evaluated, Pt-based therapies were recommended in more than half of the 18 ICD-O topographic categories, with guideline coverage ranging from 55.6% to 83.3%. Real-world utilization data, using Bulgaria as a case study, indicated sustained and increasing use of Pt-based therapies between 2021 and 2024, with oxaliplatin showing the greatest increase. Current clinical trials focus primarily on optimizing established Pt-based regimens through combinations with immunotherapeutics and emerging drug candidates within increasingly personalized multimodal treatment strategies. In parallel, research efforts are directed toward the development of new Pt complexes, exploring next-generation approaches such as multifunctional Pt(IV) prodrugs and Pt-N-heterocyclic carbene compounds, as well as advanced drug-delivery systems, reflecting continued innovation in the field. Overall, Pt-based drugs remain essential in cancer therapy and continue to represent a dynamic area of research in biological inorganic chemistry and translational oncology.

Mössbauer parameters of low spin six coordinate [Fe(II)(Por)L2] and [Fe(II)(Por)LX] complexes (where Por is PPIX or a synthetic porphyrin; L is OH[-], H2O, a nitrogenous base, CCl2, CO or CN[-] and X is a different ligand to L) are discussed. Our point charge calculation approach is extended to investigate how the axial ligands and the four porphyrinato-N atoms generate the observed quadrupole splittings (ΔEQ). Partial quadrupole splitting (p.q.s.) and partial centre shift (p.c.s.) values are derived and discussed for all the axial ligands studied herein. It is shown that when the D4h symmetry breaks down due to porphyrin ring ruffling, the point charge calculations no longer apply. This happens for many synthetic porphyrins but not for the uniquely important [Fe(II)(PPIX)] moiety, (which is ubiquitous in nature). Thus, synthetic porphyrins (like TPP) cannot always act as perfect proxies for natural haem proteins. In all the haem proteins containing [Fe(II)(PPIX)] moieties the haem is planar. Calculations indicate that if H2O were bound to the [Fe(II)(PPIX))] present in deoxyhaemoglobin or deoxy myoglobin, then these Fe(II) atoms would be low spin. In contrast for synthetic and natural haem proteins containing haem b (where the haem is connected to the protein backbone via two cysteine residues) the haem plane is ruffled (probably because of the methionine linkages transferring force and controlling the stereochemistry of the haem plane, and thereby its chemistry). For the [Fe(II)(TPP)(CN)2] and [Fe(II)(TPP)(1-MeIm)(CN)] the calculated CN[-] ligand p.q.s values are suspect and probably show that the lattice charge is affecting them.

Cytochrome c biogenesis in bacteria relies on complex membrane-bound machineries that facilitate the covalent attachment of heme to apocytochrome c. System II, mediated by the bifunctional protein CcsBA, is prevalent in Gram-positive and some Gram-negative bacteria, as well as chloroplasts. Here, we report a 2.9 Å resolution cryo-EM structure of a W703C mutant of CcsBA from Bacteroides thetaiotaomicron, revealing its conformation in the heme-loaded, closed state. Comparative analysis with the previously published Helicobacter hepaticus CcsBA structure shows a conserved membrane architecture and WxWD domain organization, but notable differences in the arrangement of the periplasmic domain and the active site configuration. The W703C mutation allowed heme occupancy in the active site without inducing the open conformation, implicating the native W703 in regulating structural transitions critical for heme attachment. Our findings suggest that while the open conformation facilitates heme ligation, it is not essential for heme translocation. This work expands the understanding of structure-function relationships in System II cytochrome c maturation and highlights the potential regulatory role of the periplasmic domain conformational dynamics.

Candida species are opportunistic yeasts and the leading cause of invasive fungal infections in hospitals. These infections are associated with high morbidity and mortality and impose a significant burden on patients and healthcare systems. Their severity is exacerbated by the limited number of effective therapeutics and the growing prevalence of antifungal resistance, underscoring the urgent need for agents with novel mechanisms of action. In this work, we synthesized two half-sandwich iridium(III) complexes with the general formula [Ir(η[5]-Cp*)Cl(N, N)]X, where the N, N-chelating ligand is 1,10-phenanthroline-5,6-dione. The complexes differ only in the counterion (X): triflate for Ir1 and chloride for Ir2. Both complexes exhibited activity against all tested medically relevant fungi; however, their antifungal potency was strongly influenced by the nature of the counterion, with the triflate-containing complex Ir1 displaying superior efficacy and MIC values ranging from 0.3 to 0.5 µM against Candida spp. In vitro, Ir1 outperformed the clinically used antifungals caspofungin and fluconazole and retained activity against fluconazole-resistant strains. Ir1 also inhibited biofilm formation and appears to act, at least in part, by inducing reactive oxygen species (ROS). Remarkably, Ir1 exhibited low in vivo toxicity and effectively treated invasive Candida albicans infections in a zebrafish embryo model of disseminated candidiasis.

Proton transfer is essential in all multi-electron transformations. Identifying the proton donor in such processes is crucial to understanding the catalytic mechanism and optimizing activity through pKa matching, which can enhance proton transfer rates. However, aqueous solutions offer multiple proton sources, which confounds clear identification of the catalytically relevant proton donor. In this work, we utilize a model hydrogenase, nickel-substituted rubredoxin (NiRd), which is capable of electrocatalytic hydrogen evolution. Prior mechanistic studies suggested a proton transfer process was involved in the rate determining step on the basis of isotopic substitution and kinetic modeling. In this study, the identity of the proton donor in this rate-determining step was investigated by employing a range of buffers with varied pKa values. The impacts of concentration and pH on catalytic currents and turnover frequencies (TOF) were investigated. These results suggest that intermolecular, buffer-dependent proton transfer is not the rate-determining step for catalysis under typical electrocatalytic conditions. Quantitative electrochemical simulations incorporating buffer information allowed extraction of intrinsic thermodynamic and kinetic parameters for catalysis. Ultimately, mechanistic distinctions between the NiRd system and other hydrogen-evolving catalysts suggest that controlling the proton donor may serve as a handle for modulating activity in an intentional manner.

Certain Clostridium pasteurianum strains encode up to four FeFe-hydrogenases, which are homologous (identity > 20%) but can be readily distinguished by their number of residues (450-550), the nature and number of accessory iron-sulfur clusters (up to four), and the composition of the so-called P1 motif (TSCCP in CpI and CpII, TSCCCP in CpIII, or NSCCP in CpIV). CpI is one of the most extensively characterized FeFe-hydrogenases; here we compare it with CpII using protein film electrochemistry, the technique invented and popularised by Fraser Armstrong in Oxford. In this approach the enzyme is wired to an electrode and then interrogated to obtain information on their catalytic responses and reactions with the inhibitors. With the aim of elucidating the relation between structure and function within the FeFe-hydrogenase family, we also examined the effects of replacing three CpII residues with the corresponding residues from CpI: S99A, near the active-site dinuclear cluster; T377A, between the cubane and the proximal cluster; and S73A, near the distal cluster. Small effects are observed on the catalytic bias (S99A) and the Michaelis constant for H2 (S99A), but not on the irreversibility of the catalytic response of CpII. The most significant changes concern the reaction with O2: unlike CpI, CpII reacts fully irreversibly with O2; the T377A and S99A mutations significantly slow this reaction, whereas the S73A mutation makes it more reversible. These findings have far-reaching implications for ongoing research aimed at understanding why homologous hydrogenases exhibit distinct catalytic properties, by suggesting that these differences likely arise from a combination of small changes rather than a single underlying cause.

Ergothioneine biosynthesis relies on the non-heme Fe(II) sulfoxide synthase EgtB, which couples O2 activation to stereoselective C-S bond formation between trimethylhistidine (TMH; hercynine) and L-cysteine (L-Cys). Here, we utilize circular dichroism (CD), differential scanning fluorescence, light scattering, and stopped-flow spectroscopy to define how metal loading, substrate addition, oxygen availability, and pH shape the active site and catalysis of tetrameric EgtB from Chloracidobacterium thermophilum (Cth). Far-UV CD and thermal unfolding data confirm CthEgtB's stable, predominantly alpha helical secondary structure under all conditions studied, while Fe(II) and sequential substrate binding help to stabilize the enzyme. Visible CD demonstrates a distinct ligand-field reorganization upon sequential addition of Fe(II), L-Cys, and TMH to apo-CthEgtB. Subsequent exposure to O2 results in a shift of the ligand-field and charge-transfer features with associated appearance of a high energy feature consistent with the formation of sulfoxide product. The pH- and temperature-dependent kinetics of the reaction were monitored via stopped-flow absorption spectroscopy and show max activity at pH 7.0 and rates that scale with O2 concentration, indicating tightly coupled O2 binding and activation. Mass spectrometry confirms oxygen dependent formation of the hercynylcysteine sulfoxide product. Finally, we provide clear evidence that retention of a 6x N-terminal histidine-tag decreases the activity and stability of CthEgtB, confirming that tagged constructs do not fully reproduce native behavior. Together, these results support a unified mechanism in which Fe(II), substrate binding, protonation environment around the active site, and O2 availability poise the CthEgtB active site for efficient oxygen activation and sulfoxide formation.