📋 Browse Articles

In this study, Ni(II) and Co(II) complexes [Co(H2O)2L2] (1), [Ni(H2O)2L2] (2), [Co(phen)L2] (3), [Ni(phen)L2]·2H2O·EtOH (4·2H2O), and [Ni(phen)2(H2O)L]·L·2H2O (5), where L—4,5-dichloro-isothiazole-3-carboxylate anion and phen—1,10-phenanthroline are reported. All complexes have been characterized by physicochemical and spectroscopic methods. Mass spectrometry and UV–Vis spectroscopy have been used to show the behavior of complexes in ethanol solution and phosphate buffer saline. Crystal structures of mononuclear complexes 1, 4 and 5 have been determined by single-crystal X-ray diffraction. In the structure of 4, mononuclear units have been found to form infinite zigzag chains due to the presence of Cl•••Cl non-covalent interactions which can be regarded as halogen bonding. All complexes have been screened in vitro for their cytotoxic activity against Hep2 cancer cell line. The complexes obtained showed no activity (IC50 > 50 µM) in comparison with structurally related Cu(II) complex [Cu(phen)(H2O)L2] exhibiting dose-dependent toxicity comparable to that of cisplatin (IC50 = 3.06 ± 0.07 µM (Cu(II) complex), IC50 = 9.2 ± 0.5 µM (cisplatin)). DNA binding constants were determined using absorption titration: Cu(II), Ni(II) and Co(II) complexes possessed similar DNA binding efficacy (Kb ~ 104). Show less

Abstract As a kind of multifunctional materials with high porosity, tunable pore structure and easy functionalization, coordination complexes have been widely used in various fields. Here, three complexes were prepared by self‐assembly with Co(II) ions using tetrazolylacetic acids as ligands, 2,2′,2′′‐(benzene‐1,3,5‐triyltris(2 H ‐tetrazole‐5,2‐diyl)) triacetic acid (H 3 tzpha), 2‐(5‐(pyrazin‐2‐yl)‐2 H ‐tetrazol‐2‐yl) propanoic acid (Hpztzma) and 2‐(5‐(pyridin‐2‐yl)‐2 H ‐tetrazol‐2‐yl) acetic acid (Hpytza), and were characterized by X‐ray crystallography. These complexes can also self‐assemble into nanoparticles (NPs) in aqueous solution by nanocoprecipitation. In vitro CCK‐8 assay on three kind of human cancer cells (HeLa, HepG2 and Huh7) cells showed these Co(II) complexes have the best cytotoxicity against HeLa cells. And complex 1 had a half maximal inhibitory concentration (IC 50 value) of 14.8 μg mL −1 , which was superior to 16.5 μg mL −1 and 15.2 μg mL −1 of complex 2 and 3 . In addition, the effect of different ligands on cancer cell ablation was explored. The results showed the three NPs can effectively inhibit the proliferation of cancer cells in vitro and provided a strategy on designing highly efficient anticancer materials based on coordination complexes. Show less

Abstract The crystal structure of the Cu(II) binuclear complex with 5-phenyltetrazole and 4,4'-dimethyl-2,2'-bipyridine (dmbipy), [Cu2(dmbipy)2L4], has been determined. The complex crystallizes in a monoclinic space group P21/c. The distorted square-pyramidal environment of Cu(II) atoms is formed by five nitrogen atoms belonging to three 5-phenyltetrazolate anions and one dmbipy molecule. Due to the presence of the intermolecular interactions π···π and C–H···π, the binuclear molecules combine into a supramolecular layered structure. The bonding energy has been calculated in terms of the density functional theory for two models of the [Cu2(dmbipy)2L4] complex with various coordination modes of the bridging 5-phenyltetrazole. Show less

Transition metal coordination complexes have provided cancer treatment with new insights to overcome the limitations of current chemotherapeutic agents. Utilization of bifunctional tetrazole–carboxylate ligands with Zn(II) obtained two self-assembled complexes [Zn(HL1)(bipy)3/2(H2O)]·CH3OH·4(H2O) (1) (H3L1 = 1,3,5-tri(2-carboxymethyltetrazol-5-yl) benzene) and [Zn(L2)2(H2O)2]2·2H2O (2) (HL2 = (5-pyridin-3-yl-tetrazol-2-yl)-acetic acid). The X-ray diffraction results showed that the two complexes displayed a two-dimensional (2D) layer structure and a one-dimensional (1D) layer structure. Nanocoprecipitation with DSPE-PEG-2000 resulted in the formation of complex nanoparticles (NPS) with excellent water dispersion. In vitro CCK-8 assay indicated the two NPs exert high cytotoxicity and sensitivity and a low half-maximum inhibitory concentration (IC50) towards HeLa than HepG2 cells. In addition, the cytotoxicity was also confirmed by live/dead co-stained experiments. The presented experimental results showed the 1 and 2 NPs were capable of inhibiting cell proliferation in vitro and may help design coordination complex-based anticancer candidates for cancer cells. Show less

Stimulation of plasma membrane receptor tyrosine kinases (RTKs), such as the epidermal growth factor receptor (EGFR), locally increases the abundance of reactive oxygen species (ROS). These ROS then oxidize cysteine residues in proteins to potentiate downstream signaling. Spatial confinement of ROS is an important regulatory mechanism of redox signaling that enables the stimulation of different RTKs to oxidize distinct sets of downstream proteins. To uncover additional mechanisms that specify cysteines that are redox regulated by EGF stimulation, we performed time-resolved quantification of the EGF-dependent oxidation of 4200 cysteine sites in A431 cells. Fifty-one percent of cysteines were statistically significantly oxidized by EGF stimulation. Furthermore, EGF induced three distinct spatiotemporal patterns of cysteine oxidation in functionally organized protein networks, consistent with the spatial confinement model. Unexpectedly, protein crystal structure analysis and molecular dynamics simulations indicated widespread redox regulation of cryptic cysteine residues that are solvent exposed only upon changes in protein conformation. Phosphorylation and increased flux of nucleotide substrates served as two distinct modes by which EGF specified the cryptic cysteine residues that became solvent exposed and redox regulated. Because proteins that are structurally regulated by different RTKs or cellular perturbations are largely unique, these findings suggest that solvent exposure and redox regulation of cryptic cysteine residues contextually delineate redox signaling networks. Show less

AbstractGuanine quadruplex recognition has gained increasing attention, inspired by the growing awareness of the key roles played by these non‐canonical nucleic acid architectures in cellular regulatory processes. We report here the solution and solid‐state studies of a novel planar platinum(II) complex that is easily assembled from a simple ligand, and exhibits notable binding affinity for guanine quadruplex structures, while maintaining good selectivity for guanine quadruplex over duplex structures. A crystal structure of this ligand complexed with a telomeric quadruplex confirms double end‐capping, with dimerization at the 5′ interface. Show less

Abstract A series of palladium(II) complexes with 1H- and 2H-tetrazole ligands (2-isopropyl-5-R-2H-tetrazoles and 1H-tetrazol-1-ylcarboxylic acids) was synthesized. Structure of the obtained compounds was confirmed by 1H and 13C NMR spectroscopy, high-resolution mass spectrometry, and single crystal X-ray diffraction analysis. According to the spectrophotometry data, the complexes are weakly bound to DNA. The cytotoxic activity of the obtained palladium complexes was studied in vitro. Show less

The X-ray crystal structure of the d(CGCGCG)2/putrescine(2+)/K+ complex has been determined at 0.60 Å resolution. Stereochemical restraints were used only for the putrescinium dication, and 23 bonds and 18 angles of the Z-DNA nucleotides with dual conformation. The N atoms of the putrescine(2+) dication form three direct hydrogen bonds with the N7_G atoms of three different Z-DNA molecules, plus three water-mediated hydrogen bonds with cytosine, guanine and phosphate acceptors. A unique potassium cation was also unambiguously identified in the structure, albeit at a ∼0.5 occupation site shared with a water molecule, providing the first example of such a complex with Z-DNA. The K+ cation has coordination number of eight and an irregular coordination sphere, formed by four water molecules and four O atoms from two phosphate groups of the Z-DNA, including ligands present at fractional occupancy. The structural disorder of the Z-DNA duplex is manifested by the presence of alternate conformations along the DNA backbone. Comparison of the position and interactions of putrescine(2+) in the present structure with other ultra-high-resolution structures of Z-DNA in complexes with Mn2+ and Zn2+ ions shows that the dicationic putrescinium moiety can effectively substitute these metal ions for stabilization of Z-type DNA duplexes. Furthermore, this comparison also suggests that the spermine(4+) tetracation has a higher affinity for Z-DNA than K+. Show less

The stable complex [bis(toluene-3,4-dithiolato)copper(III)][NEt3H] has been synthesised and characterised as a square-planar Cu(III) complex by X-ray photoelectron spectroscopy, cyclic voltammetry and DFT calculations. Intriguingly, when fragmented in FTICR-MS, an unusual [(toluene-3,4-dithiolate)Cu(III)(peroxide)]− complex is formed by reaction with oxygen. Natural 1,2-dithiolenes known to bind molybdenum might stabilise Cu(III) in vivo. Show less

The functions, purposes, and roles of metallothioneins have been the subject of speculations since the discovery of the protein over 60 years ago. This article guides through the history of investigations and resolves multiple contentions by providing new interpretations of the structure-stability-function relationship. It challenges the dogma that the biologically relevant structure of the mammalian proteins is only the one determined by X-ray diffraction and NMR spectroscopy. The terms metallothionein and thionein are ambiguous and insufficient to understand biological function. The proteins need to be seen in their biological context, which limits and defines the chemistry possible. They exist in multiple forms with different degrees of metalation and types of metal ions. The homoleptic thiolate coordination of mammalian metallothioneins is important for their molecular mechanism. It endows the proteins with redox activity and a specific pH dependence of their metal affinities. The proteins, therefore, also exist in different redox states of the sulfur donor ligands. Their coordination dynamics allows a vast conformational landscape for interactions with other proteins and ligands. Many fundamental signal transduction pathways regulate the expression of the dozen of human metallothionein genes. Recent advances in understanding the control of cellular zinc and copper homeostasis are the foundation for suggesting that mammalian metallothioneins provide a highly dynamic, regulated, and uniquely biological metal buffer to control the availability, fluctuations, and signaling transients of the most competitive Zn(II) and Cu(I) ions in cellular space and time. Show less

Two new arene ruthenium(II) complexes with chemical formula [Ru2(η6‐p‐cymene)2(μ‐L1)(μ‐Cl)Cl2][Ru]‐1and [Ru(η6‐p‐cymene)(L2)Cl2][Ru]‐2(L1 =5‐phenyl‐2H‐tetrazole andL2= 2‐(2H‐tetrazol‐5‐yl)pyridine) were synthesized by the reaction of [{(η6‐p‐cymene)RuCl2}2] with two bidentate ligands L1 and L2. Both the complexes were structurally characterized using single‐crystal X‐ray diffraction and other analytical techniques. The X‐ray crystal structures of both the complexes revealed the coordination of tetrazolate ligands to two Ru(II) centres in bridging mode in[Ru]‐1, whereas one Ru(II) centre in[Ru]‐2in chelating fashion, with overall pseudo‐octahedral geometry. The resulted complexes were screened for their cytotoxic activity against three different cancer cell lines, HCT116 (colon cancer), HepG2 (liver cancer) and MCF7 (breast cancer) under in vitro conditions. Interestingly,[Ru]‐1showed much higher cytotoxicity with respect to[Ru]‐2against all the screened cancer cell lines and even better than cisplatin. For exploring the mechanism of action of[Ru]‐1, reactive oxygen species (ROS) production, alterations in mitochondrial membrane potential and gene expression profiling of apoptosis related genes (Bcl2, caspase‐3 and caspase‐9) were also evaluated. The cancerous cells treated with[Ru]‐1showed an increase in intracellular ROS levels, disruption of mitochondrial membrane potential, up‐regulation of proapoptotic caspase‐3 and caspase‐9 and down‐regulation of antiapoptotic Bcl2. The results concluded that[Ru]‐1induced apoptosis through oxidative stress mediated activation of intrinsic pathway by generating intracellular ROS, loss of MMP and alteration of expression of apoptosis related genes. In addition, antimetastatic activity of[Ru]‐1was observed by wound healing assay showing anti‐migratory property. The dual properties, antimetastatic activity and high cytotoxicity make[Ru]‐1potent platform for the development of new anticancer agents. Show less

Herein, we describe a new family of tris chelate homoleptic Ru (II) complexes, [Ru(N^N)3]2+, where the role of the diimine‐type ligands (N^N) was fulfilled by 2‐pyridyl (PTZ) or 2‐quinolyl tetrazole (QTZ) derivatives decorated with various alkyl substituents at the N‐2 position of the tetrazole ring. The new Ru (II) complexes with general formula [Ru (PTZ‐R)3]2+ and [Ru (QTZ‐R)3]2+, were obtained as mixtures of facial (fac) and meridional (mer) isomers, as suggested by NMR (1H, 13C) experiments, and confirmed in the case of mer‐[Ru (QTZ‐Me)3]2+, by X‐ray crystallography. The photophysical behavior of the tetrazole‐based [Ru(N^N)3]2+ type species was investigated by UV–vis absorption spectroscopy, providing trends typical of polypyridyl Ru (II) complexes. The new homoleptic complexes fac/mer‐[Ru (PTZ‐R)3]2+ and fac/mer‐[Ru (QTZ‐R)3]2+ have been assessed for any eventual antimicrobial activity towards two different bacteria such as Gram‐negative Escherichia coli and Gram‐positive Deinococcus radiodurans. Whereas being inactive toward E. coli, the response of agar disks diffusion tests suggested that some of the new fac/mer Ru (II) complexes could inhibit the growth of D. radiodurans. This effect was further investigated by determining the growth kinetics in liquid medium of D. radiodurans exposed to the fac/mer‐[Ru (PTZ‐R)3]2+ and fac/mer‐[Ru (QTZ‐R)3]2+ complexes at different concentrations. The outcome of these experiments highlighted that the turn‐on of the growth inhibitory effect took place as the linear hexyl chain was appended to the PTZ or QTZ scaffold, suggesting also how the inhibitory activity appeared more pronouncedly exerted by the facial isomers fac‐[Ru (PTZ‐Hex)3]2+ and fac‐[Ru (QTZ‐Hex)3]2+ (MIC = ca. 3.0 μg/ml) with respect to the corresponding meridional isomers (MIC = ca. 6.0 μg/ml). Show less

Three novel complexes, namely [Nd·L1·HCOO·(H2O)4] (1), [Pr·L1·HCOO·(H2O)4] (2) and [In·L2·Cl·(H2O)2] (3) (L1 = 1,1‐bis(5‐(pyrazin‐2‐yl)‐1,2,4‐triazol‐3‐yl)methane, L2 = 1,1‐bis(5‐(pyrazin‐2‐yl)‐1,2,4‐triazol‐3‐yl)ketone), were synthesized and characterized. The molecular structures of 1–3 were confirmed using single‐crystal X‐ray diffraction. All three obtained complexes are zero‐dimensional and connected to each other by hydrogen bonds. In 1 and 2 the metal is surrounded by nine donors and 3 has seven coordination sites. The interaction of 1–3 with calf thymus DNA (CT‐DNA) was explored using UV absorption spectra and fluorescence spectra. The intrinsic binding constants of 1–3 with CT‐DNA are about 1.9 × 104, 1.4 × 104 and 1.1 × 104, respectively. Stern–Volmer quenching plots of 1–3 have slopes of 0.1508, 0.134 and 0.1205, respectively. The ability of these complexes to cleave pBR322 plasmid DNA was demonstrated using gel electrophoresis assay. Apoptosis studies of the three novel complexes showed a significant inhibitory effect on HeLa cells. Furthermore, MTT assays were used to evaluate the anticancer activity of the three complexes. The cytotoxicity study indicated that complex 1 possesses a higher inhibitory rate of HeLa cells than the other complexes. Especially, the efficacy of 1 was shown to be the highest for cisplatin at 24 h. A further molecular docking technique was introduced to understand the binding of the complexes toward the target DNA. Show less

Cyclic diadenylate (c-di-AMP) is a widespread second messenger in bacteria and archaea that is involved in the maintenance of osmotic pressure, response to DNA damage, and control of central metabolism, biofilm formation, acid stress resistance, and other functions. The primary importance of c-di AMP stems from its essentiality for many bacteria under standard growth conditions and the ability of several eukaryotic proteins to sense its presence in the cell cytoplasm and trigger an immune response by the host cells. We review here the tertiary structures of the domains that regulate c-di-AMP synthesis and signaling, and the mechanisms of c-di-AMP binding, including the principal conformations of c-di-AMP, observed in various crystal structures. We discuss how these c-di-AMP molecules are bound to the protein and riboswitch receptors and what kinds of interactions account for the specific high-affinity binding of the c-di-AMP ligand. We describe seven kinds of non-covalent-π interactions between c-di-AMP and its receptor proteins, including π-π, C-H-π, cation-π, polar-π, hydrophobic-π, anion-π and the lone pair-π interactions. We also compare the mechanisms of c-di-AMP and c-di-GMP binding by the respective receptors that allow these two cyclic dinucleotides to control very different biological functions. Show less

Bis-ADC complexes cis-[Pd{C(NHC6H4NH2)N(H)R}2]Cl2 (R = Xyl 4a, Cy 4b, C6H4-4-F 4c) and cis-[Pt{C(NHC6H4NH2)N(H)R}2]Cl2 (R = Xyl 5a, Cy 5b, C6H4-4-F 5c) were synthesized via the metal-mediated coupling of two isocyanide ligands in cis-[MCl2(CNR)2] (M = Pd, Pt; R = Xyl, Cy, C6H4-4-F) and 1,2-diaminobenzene. New compounds 4c and 5a–c were characterized by HR ESI+-MS, IR, and 1H, 13C{1H} and 195Pt{1H} NMR spectroscopy; the structures of 4a and 5a were elucidated by single-crystal X-ray diffraction. The stability of the ADC complexes in aqueous media (5 mM NaCl) was monitored by UV absorption spectroscopy, HR ESI+ mass spectrometry, and 195Pt{1H} NMR spectroscopy (for 5a). Molar conductivity measurements in MeOH (ΛM = 167–173 Ω−1 mol−1 cm2) indicate that, in this solvent, the ADC complexes exist as dicationic species of [A][Q]2 type. The ADC complexes binding to CT DNA was investigated by means of spectroscopic and hydrodynamic techniques including UV absorption and circular dichroism spectroscopy, fluorescence spectroscopy, low-gradient viscometry, flow birefringence, and AFM imaging. As a result, complexes 4a and 5a were shown to bind double-stranded DNA predominantly via the formation of monofunctional adducts in the major groove of the macromolecule. Binding of the ADC complexes also provokes the formation of a large number of intermolecular DNA–DNA contacts in solution. The antiproliferative activity of all prepared ADC complexes 4a–c and 5a–c was evaluated in vitro against three human carcinoma cell lines (HT-29, MDA-MB-231, and MCF-7) and two non-tumorigenic cell lines (L929 and RC-124) and compared to that of cisplatin. Among the compounds studied, complexes 4a and 5a appeared to be the most active species with IC50 values in MCF-7 cells of about 10 μM. Show less

Two new coordination complexes of Cu(II) and Mn(II), viz., [Cu(bpy)(H2O)4]SO4·2H2O (1) and [Mn(4-CNpy)2(H2O)3SO4]·H2O (2) (bpy = 2,2′-bipyridine, 4-CNpy = 4-cyanopyridine), have been synthesized and characterized by using single crystal X-ray diffraction, elemental analysis, FT-IR spectroscopy, electronic spectroscopic techniques and TGA. The crystal structure of 1 uncovers the formation of sulfate–water assemblies involving lattice and coordinated water molecules, while complex 2 reveals the presence of unconventional weak T-shaped CN⋯CN contacts in the layered architecture. We have analysed the unconventional interesting interactions using DFT calculations, molecular electrostatic potential (MEP), the NCI plot and QTAIM computational tools. The interaction energies of the two H-bonded dimers in 1 are very large because of the coulombic attraction between the dicationic H-bonded donor and the dianionic acceptor. It is interesting to observe that despite the energy of the H-bonds being very small compared to the total dimerization energy, the final geometry of the assembly in 1 is due to the charge assisted directional H-bonds instead of the non-directional ion-pair interactions. The DFT study reveals that the T-shaped CN⋯CN interaction in 2 is very weak, in good agreement with the small MEP energy at the nitrile carbon atom. Anticancer studies of the compounds have been carried out using Dalton's lymphoma cell line using MTT and apoptosis assay. The results of compound 1 and 2 mediated cell cytotoxicity on the DL cancer cell line showed a significant concentration-dependent reduction in cell viability, while negligible cytotoxicity was observed in normal (PBMC) cells. The docking simulation results also confirm the interaction of the complexes with the active sites of amino acids of the target proteins. Furthermore, pharmacophore models (2D and 3D) for the compounds were mapped to the H-bond donor, positive ionisable area and hydrophobic features that are important for establishing biological activities. No hematotoxicity was recorded for the compounds after treatment in normal mice. Show less

XPD is part of the TFIIH complex which plays major roles in transcription initiation and nucleotide excision repair (NER). Here the authors present a high-resolution crystal structure of the XPD-MAT1 interface and dissect the role of this interface in transcription and NER. Show less

The DNA in the left-handed conformation (Z-conformation) was first discovered by A. Rich, who revealed the crystalline structure of a DNA oligomer d(GC)3 by X-ray diffraction method. Later it was also found that DNA molecules change their conformations from typical right-handed form (B-DNA) to the left-handed form (Z-DNA) under specific conditions (B–Z transition). Furthermore, the detailed structures of the interface between B- and Z-DNAs, B-Z junction, was also determined with an atomic resolution. Recently it was found that some proteins have the Z-DNA binding domains, but the biological functions of Z-DNA are not well understood yet. Therefore the investigation of Z-DNA under physiological conditions is highly essential. In this study, we demonstrated the high-resolution real-space imaging of DNA molecules having the Z- and B-form conformations by frequency-modulation atomic force microscopy (FM-AFM), that has made a great progress in recent years, in an aqueous solution. The major and minor grooves of both DNA conformations were clearly visualized. Furthermore, the surface charge density was measured by three-dimensional (3D) force mapping method. We found that Z-form region was less negatively charged than the B-form region. Show less

The crystal structure of BZ-junction reveals that left-handed Z-DNA stabilized by Z-DNA binding domain (Zα) is continuously stacked to right-handed B-DNA with AT bases' extrusion in the junction site. However, this structure might not fully represent the BZ-junction in solution due to the possibility of the junction formation either by crystal packing or Zα interaction. Therefore, we investigated BZ-junction in solution with chemical Z-DNA inducers using CD and 2-aminopurine base-extrusion assay. We confirmed the formation of Z-DNA and BZ-junction with base-extrusion by chemical Z-DNA inducers. However, neither typical Z-DNA nor base-extrusion could be detected with some inducers such as spermine, suggesting that the energy barrier for the formation of the BZ junction might vary depending on the Z-DNA induction conditions. Show less

AbstractThe covalent nature of the low‐barrier N−H−N hydrogen bonds in the negative thermal expansion material H3[Co(CN)6] has been established by using a combination of X‐ray and neutron diffraction electron density analysis and theoretical calculations. This finding explains why negative thermal expansion can occur in a material not commonly considered to be built from rigid linkers. The pertinent hydrogen atom is located symmetrically between two nitrogen atoms in a double‐well potential with hydrogen above the barrier for proton transfer, thus forming a low‐barrier hydrogen bond. Hydrogen is covalently bonded to the two nitrogen atoms, which is the first experimentally confirmed covalent hydrogen bond in a network structure. Source function calculations established that the present N−H−N hydrogen bond follows the trends observed for negatively charge‐assisted hydrogen bonds and low‐barrier hydrogen bonds previously established for O−H−O hydrogen bonds. The bonding between the cobalt and cyanide ligands was found to be a typical donor–acceptor bond involving a high‐field ligand and a transition metal in a low‐spin configuration. Show less

The coupling of bis(xylylisocyanide) complex of Pd(II) with 1,2,4-thiadiazole-5-amines leads to the formation of an equilibrium mixture of the binuclear complexes. In each of the studied cases, one of the formed complexes is the kinetic product, and the other one is the thermodynamic product. The complexes which are thermodynamic products have been isolated in the pure form and characterized by means of high-resolution mass spectrometry, IR and NMR spectroscopy, and X-ray diffraction analysis. NMR study of the regioisomerization in a solution has revealed that the relative stability of the thermodynamic products in comparison with the kinetic ones is higher than for the corresponding regioisomers containing 1,3-thiazole or 1,3,4- thiadiazole fragment. Show less

RuII compounds have been universally investigated due to their unique physical and chemical properties. In this paper, a new RuII compound based on 2,2′‐bipy and Hpmtz [2,2′‐bipy = 2,2′‐bipyridine, Hpmtz = 5‐(2‐pyrimidyl)‐1H‐tetrazole], namely [Ru(2,2′‐bipy)2(pmtz)][PF6]·0.5H2O was prepared and characterized by elemental analysis, IR and single‐crystal X‐ray diffraction. [Ru(2,2′‐bipy)2(pmtz)][PF6]·0.5H2O shows a mononuclear structure and forms a three‐dimensional network by non‐classic hydrogen bonds. The ability of generation of ROS (reactive oxygen species) makes it has a low phototoxicity IC50 (half‐maximal inhibitory concentration) after Xenon lamp irradiation on Hela cells in vitro. The results demonstrate that [Ru(2,2′‐bipy)2(pmtz)][PF6]·0.5H2O with high light toxicity and low dark toxicity may be a potential candidate for photodynamic therapy. Show less

Mitochondrial calcium uptake plays critical roles in regulating ATP production, intracellular calcium signaling, and cell death. This uptake is mediated by a highly selective calcium channel called the mitochondrial calcium uniporter. Here, we determined the structures of the pore-forming MCU proteins by X-ray crystallography and single-particle cryo-electron microscopy. The stoichiometry, overall architecture, and individual subunit structure differed markedly from those in the recent nuclear magnetic resonance structure of the Caenorhabditis elegans MCU. In our studies, we observed a dimer-of-dimer architecture across species and chemical environments, which was corroborated by biochemical experiments. Structural analyses and functional characterizations uncovered the roles of critical residues in the pore. These results reveal a new ion channel architecture, provide insights into calcium coordination, selectivity, and conduction, and establish a structural framework for understanding the mechanism of mitochondrial calcium uniporter function. Show less

The solution state of palladium cationic–anionic complexes (AmH n ) k [PdCl4] prepared for the first time, where Am is morpholine, methylmorpholine, aminoethylmorpholine, 5-aminovaleric acid, L-1-phenyl-2-methylaminopropanol, and m-xylilenediamine, has been studied by electronic absorption spectroscopy, NMR, and pH measurements. The agreement of obtained results for the state of the complexes in water and NaCl solutions with IR and X-ray diffraction data for these complexes has allowed us to substantiate the principle for designing patent formulation (C5H12NO)2[PdCl4], a new type of palladium complexes, palladium(II) cationic–anionic complexes showing high antitumor and antimetastatic activity. Crystallographic data for six obtained complexes have been presented. Show less