Crystal Structure Of Complex Research Articles

Synthesis, Crystal Structures and Catalytic Oxidation Property of Two Copper(II) Complexes Derived from 5-Bromo-2-((2-piperazin-1-ylethylimino)methyl)phenol.

Two new copper(II) complexes, [Cu(HL)(ONO2)]NO3 (1) and [CuCl(HL)]Cl∙H2O (2), where HL is the zwitterionic form of the Schiff base 5-bromo-2-((2-piperazin-1-ylethylimino)methyl)phenol (HL), have been prepared. The Schiff base and two complexes were characterized by IR and UV-Vis spectroscopy. In addition, the free Schiff base was characterized by 1H NMR spectroscopy. Structures of the complexes were further confirmed by single crystal X-ray diffraction. The Cu atoms in the complexes are in square planar coordination. Crystal structures of both copper complexes are stabilized by hydrogen bonds. The complexes have high catalytic activity for the epoxidation of styrene, with conversions and selectivity over 90%.

Enhanced Thermoelectric Performance in Cu7Sn3S10‐based Hybrid Materials with Highly Dispersed Multiwalled Carbon Nanotubes

AbstractTernary copper chalcogenide Cu7Sn3S10 has attracted great attention due to its complex and tunable crystal structure, good thermoelectric performance, and earth‐abundant and eco‐friendly elements. However, the optimization of thermoelectric performance in Cu7Sn3S10 is greatly restricted because the strategy of element doping to tune electrical and thermal transports is only limited by halogen elements. Here, highly dispersed multiwalled carbon nanotubes (MCNTs) are introduced into Cu7Sn3S10 to realize hybrid materials with enhanced thermoelectric performance. A series of Cu7+ySn3S10/x wt.% MCNTs hybrid materials are successfully fabricated by ball milling combined with spark plasma sintering. The high‐purity Cu7Sn3S10/MCNTs hybrid materials are identified as polymorphs simultaneously crystalizing in tetragonal, primitive cubic, and face‐centered cubic structures. Such complex phase structures can produce lots of intrinsic cation‐disorders, phase interfaces, grain boundaries, and Cu7Sn3S10/MCNTs heterointerfaces, which can strengthen phonon and carrier scattering, while the heterointerfaces can serve as carrier reservoirs to trap holes to reduce the carrier concentration toward the optimal range. Combining these effects, both lattice thermal conductivity and carrier thermal conductivity are significantly reduced. Correspondingly, a maximum figure of merit zT of 0.65 is achieved in Cu7.05Sn3S10/2wt.% MCNTs at 750 K, about twice as compared with the MCNTs‐free Cu7Sn3S10. This work suggests that hybrid materials with well dispersed MCNTs can greatly enhance the material's thermoelectric performance.

Bonding Heterogeneity and Nanoprecipitation on Substituting the Anionic Framework in Mg3Sb2 for p‐Type Zintl Thermoelectrics

Designing zintl compounds with complex crystal structures and large unit cells containing heavy elements may inherit bonding heterogeneity‐induced lattice anharmonicity, leading to intrinsically low thermal conductivity. In this work, alloying‐induced bonding heterogeneity in the extensively explored α‐Mg3(Sb, Bi)2 phase due to local atomic ordering, site preferences, and prevailing heterogenous interfaces is evaluated in the p‐type Mg3(Sb1−2xBixSnx)2‐based polyanionic nanocomposites for different alloying concentrations. The inherent susceptibility for partial phase transition (trigonal → monoclinic) is observed upon alloying, which is driven by alterations in bonding patterns, localized distortion, and secondary phase formation. At low alloying content (x ≤ 0.05), a trigonal (Sb, Sn) phase is observed, while for higher alloying content (x ≥ 0.1), a cubic Mg2Sn nanophase emerges. A synergistic reduction in thermal conductivity and enhanced power factor maximize the zT ≈ 0.25(±0.05) at 673 K in the optimized p‐type Mg3(Sb0.9Bi0.025Sn0.025)2 nanocomposites. The study highlights bonding heterogeneity‐induced structural transitions as an inherent challenge, where the dominant role of anionic sites becomes pivotal for determining/deriving favorable structural and functional properties in Mg3(Sb, Bi)2‐based zintl compounds.

Kinetic and structural investigation of the 4-allyl syringol oxidase from Streptomyces cavernae.

Kinetic and structural investigation of the 4-allyl syringol oxidase from Streptomyces cavernae.

Crystal structure, luminescence properties and thermochemistry of lanthanide complexes based on 2-Chloro-6-fluorobenzoic acid and Nitrogenous ligands

Crystal structure, luminescence properties and thermochemistry of lanthanide complexes based on 2-Chloro-6-fluorobenzoic acid and Nitrogenous ligands

Nasal delivery of secretory IgA confers enhanced neutralizing activity against Omicron variants compared to its IgG counterpart.

Nasal delivery of secretory IgA confers enhanced neutralizing activity against Omicron variants compared to its IgG counterpart.

Molecular recognition of the promoter DNA signature sequence by Hms1pDBD.

Molecular recognition of the promoter DNA signature sequence by Hms1pDBD.

Structural insights into the RNA binding inhibitors of the C-terminal domain of the SARS-CoV-2 nucleocapsid.

Structural insights into the RNA binding inhibitors of the C-terminal domain of the SARS-CoV-2 nucleocapsid.

De novo design of transmembrane fluorescence-activating proteins.

The recognition of ligands by transmembrane proteins is essential for the exchange of materials, energy and information across biological membranes. Progress has been made in the de novo design of transmembrane proteins1-6, as well as in designing water-soluble proteins to bind small molecules7-12, but de novo design of transmembrane proteins that tightly and specifically bind to small molecules remains an outstanding challenge13. Here we present the accurate design of ligand-binding transmembrane proteins by integrating deep learning and energy-based methods. We designed pre-organized ligand-binding pockets in high-quality four-helix backbones for a fluorogenic ligand, and generated a transmembrane span using gradient-guided hallucination. The designer transmembrane proteins specifically activated fluorescence of the target fluorophore with mid-nanomolar affinity, exhibiting higher brightness and quantum yield compared to those of enhanced green fluorescent protein. These proteins were highly active in the membrane fraction of live bacterial and eukaryotic cells following expression. The crystal and cryogenic electron microscopy structures of the designer protein-ligand complexes were very close to the structures of the design models. We showed that the interactions between ligands and transmembrane proteins within the membrane can be accurately designed. Our work paves the way for the creation of new functional transmembrane proteins, with a wide range of applications including imaging, ligand sensing and membrane transport.

Automatic identification of slip pathways in ductile inorganic materials by combining the active learning strategy and NEB method

Ductile inorganic semiconductors have recently received considerable attention due to their metal-like mechanical properties and potential applications in flexible electronics. However, the accurate determination of slip pathways, crucial for understanding the deformation mechanism, still poses a great challenge owing to the complex crystal structures of these materials. In this study, we propose an automated workflow based on the interlayer slip potential energy surface to identify slip pathways in complex inorganic systems. Our computational approach consists of two key stages: first, an active learning strategy is utilized to efficiently and accurately model the interlayer slip potential energy surfaces; second, the climbing image nudged elastic band method is employed to identify minimum energy pathways, followed by comparative analysis to determine the final slip pathway. We discuss the validity of our selected feature vectors and models across various material systems and confirm that our approach demonstrates robust effectiveness in several case studies with both simple and complicated slip pathways. Our automated workflow opens a new avenue for the automatic identification of the slip pathways in inorganic materials, which holds promise for accelerating the high-throughput screening of ductile inorganic materials.

Ru(II)-Fenamic-Based Complexes as Promising Human Ovarian Antitumor Agents: DNA Interaction, Cellular Uptake, and Three-Dimensional Spheroid Models.

Cancer resistance to chemotherapeutic agents such as cisplatin presents a significant challenge, leading to treatment failure and poor outcomes. Novel metal-based compounds offer a promising strategy to overcome drug resistance and to enhance efficacy. Four Ru(II) complexes with fenamic acid derivatives were synthesized and characterized: [Ru(L)(bipy)(dppp)]PF6, where L represents fenamic acid (HFen, complex 1), mefenamic acid (HMFen, complex 2), tolfenamic acid (HTFen, complex 3), and flufenamic acid (HFFen, complex 4). Their composition was supported by molar conductivity, elemental analysis, Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, mass spectrometry, and 31P{1H}, 1H, and 13C nuclear magnetic resonance, with the crystal structure of complex 1 confirmed via X-ray diffraction. Complexes 1-4 exhibited notable cytotoxicity against tested cell lines, particularly A2780 and A2780cisR (cisplatin-resistant ovarian tumors), compared to MDA-MB-231 (breast) and A549 (lung) lines. Mechanistic studies revealed weak DNA interactions through minor grooves or electrostatic binding. Cellular uptake assays showed effective internalization of complexes 1 (3.6%) and 2 (4.5%), correlating with potent IC50 values. These complexes also altered cell morphology, reduced cell density, and inhibited colony formation in the A2780 cells. Staining assays indicated induced cell death and organelle damage, highlighting their potential as promising antitumor agents.

Design of Luminescent Heteronuclear Au(I)‐Ag(I) Systems from Aromatic Diazines

By reaction of the polymers [Au2Ag2(C6X5)4(OEt2)2]n (X = F, Cl) with the aromatic N‐donor ligands pyrimidine and pyrazine, the new heterometallic complexes [Au2Ag2(C6X5)4(pym)]n (X = F (1), Cl (2)) and [Au2Ag2(C6X5)4(pyr)(CH3CN)2]n (X = F (3), Cl (4)) are obtained. The crystal structures of complexes 1 and 3 show the polymerization of the Au2Ag2 tetranuclear units via diazine bridging ligand between two silver centers, and also, in case of complex 1 via aurophilic interactions, leading to a two‐dimensional polymer. In all cases, the optical properties have been studied in solid state at room temperature and 77 K, showing lifetimes in the microseconds range. Finally, this study has been completed with time–dependent density functional theory calculations in the case of complexes 1 and 3 (which present two different emissions) to ascribe the origin of their emissive properties. The molecular orbitals involved in the electronic transitions responsible for the phosphorescence in the case of complex 1 are related to a ligand (C6F5) to ligand (pyrimidine) charge transfer (3LL’CT) and to a cluster metal‐centered transition (3MM’). For complex 3, these molecular orbitals consist of a mixture of a ligand–metal to ligand charge transfer ([Au(C6F5)2]–pyrazine) (3LML’CT) and an intraligand transition (within the pyrazine ligand) (3IL).

Binding of small molecules at the P-stalk site of ricin A subunit trigger conformational changes that extend into the active site.

Binding of small molecules at the P-stalk site of ricin A subunit trigger conformational changes that extend into the active site.

Local and global attention mechanisms synergy for material property prediction

Efficient machine learning (ML) models for predicting and discovering new materials present a significant challenge in materials science. Graph neural networks (GNNs) have garnered considerable attention due to their advantages in material applications. However, many GNNs fall short in representing the topological and geometric structures of crystals, leading to limited accuracy in characterising complex structures and predicting properties. This deficiency can lead to insufficient accuracy in capturing the intricate structural information of crystals, thus limiting the effectiveness of GNNs in characterising complex crystal structures and predicting their properties. To address this challenge, we introduce a dual-level attention crystal graph neural network with enhanced topological-geometric information (TGCGNN) for predicting the properties of crystalline materials. TGCGNN integrates a topologically and geometrically enhanced crystal graph attention layer (GeoGAT) with a global attention layer. The GeoGAT layer learns the topology and spatial geometry of crystals by incorporating the distance vectors between nodes and their neighbours, as well as bond lengths. Additionally, the global attention layer incorporates crystal composition to assess the collective contributions of atoms to the material properties. Through numerous experiments, we demonstrate that TGCGNN outperforms several state-of-the-art models, offering significant improvements in the accuracy of material property prediction.

Structural basis of ssDNA-guided NADase activation of prokaryotic SPARTA system.

Short prokaryotic Argonaute and the associated TIR-APAZ (SPARTA) proteins constitute a prokaryotic immune system, mediating RNA- or DNA-guided target single-stranded DNA (ssDNA) to activate NADase activity and induce cell death by degrading NAD+ in response to invading plasmids. Although the guide RNA-mediated targeting mechanism of SPARTA has been established, the functional role and mechanisms of guide DNA-mediated SPARTA remain poorly understood. Here, we report two crystal structures of Crenotalea thermophilaSPARTA complexes with 5'-phosphorylated 21-nt guide DNA and complementary target ssDNA lengths of 15or 20nt. The structures demonstrate specific recognition of the 5'-OH or 3'-OH groups in target DNA by SPARTA, while not recognizing the 5'-P group in guide DNA. This suggests distinct recognition models for guide DNA and guide RNA, indicating different activation mechanisms. Furthermore, these two structures reveal disparate models for recognizing guide DNA and target DNA, providing insights into the length requirement for SPARTA activation.

Unraveling the Determinant Mechanisms in Flow-Mediated Crystal Growth and Phase Behaviors

To uncover the critical mechanisms responsible for mesoscopic level development during flow-mediated crystal growth, we develop a semi-two-way hydrodynamic coupled structural phase-field crystal formalism (HXPFC-s2). The new formalism, inspired by previous attempts at coupling hydrodynamic and phase-field crystal (PFC) equations, allows for studying mesoscopic flow-mediated crystallization at diffusive timescales pertinent to industrial applications. Unlike previous efforts, the devised coupling to the structural PFC (XPFC) equations allows generalization to more complex crystal structures through explicit parameterization of the direct correlation function (DCF). Utilizing the HXPFC-s2 formalism, we seek to uncover the determinant physical mechanisms in crystallization under simple shear flows by comparing temperature-driven crystallization to flow-mediated crystallization under varying flow-strengths. Parallels and deviations of under-cooling and flow-strength effects on crystal growth are drawn using the crystal cluster-size and system ordering time evolutions. In doing so, we identify scaling behaviors with a Peclet-like number, Pe˜, a critical Peclet-like number, Pe˜*, and flow-field-crystal plane-dependent interactions. Our findings may be relevant for controlling crystal growth and phase behaviors in flow applications.

Synthesis, characterization and computational studies of the triangle shape complex of silver nitrate with 2-amino-1,3,4-thiadiazole

Synthesis, characterization and computational studies of the triangle shape complex of silver nitrate with 2-amino-1,3,4-thiadiazole

The structural biology of deoxyhypusination complexes.

The structural biology of deoxyhypusination complexes.

Effect of azide co-ligand on the crystal structures of rhodium and iridium metal complexes featuring pyridine-based thiourea derivatives: Characterization and in vitro biological studies

Effect of azide co-ligand on the crystal structures of rhodium and iridium metal complexes featuring pyridine-based thiourea derivatives: Characterization and in vitro biological studies

Role of the Mobile Active Site Flap in IMP Dehydrogenase Inhibitor Binding.

Inosine 5'-monophosphate dehydrogenase (IMPDH) is a promising antibiotic target. This enzyme catalyzes the NAD-dependent oxidation of inosine 5'-monophosphate (IMP) to xanthosine 5'-monophosphate (XMP), which is the rate-limiting step in guanine nucleotide biosynthesis. Bacterial IMPDH-specific inhibitors have been developed that bind to the NAD+ site. These inhibitors display varied affinities to different bacterial IMPDHs that are not easily rationalized by X-ray crystal structures of enzyme-inhibitor complexes. Inspection of X-ray crystal structures of 25 enzyme-inhibitor complexes, including 10 newly described, suggested that a mobile active site flap may be a structural determinant of inhibitor potency. Saturation transfer difference NMR experiments also suggested that the flap may contact the inhibitors to varying extents in different IMPDHs. Flap residue Leu413 contacted some inhibitors but was not structured in the crystal structures of other inhibitor complexes. The substitution of Leu413 with Phe or Ala in Bacillus anthracis IMPDH had inhibitor-selective effects, suggesting residue 413 could be a structural determinant of affinity. Curiously, the Ala substitution increased the potency of most inhibitors, even those that contacted Leu413 in the crystal structures. Presteady-state and steady-state kinetics experiments showed that the Leu413Ala substitution had comparable effects on inhibitor binding to the noncovalent E·IMP complex and the covalent intermediate E-XMP*, suggesting that the flap had similar interactions in both complexes. These results demonstrate that contacts do not necessarily indicate favorable interactions, and poorly structured mobile regions should not be discounted when assessing binding determinants.