Spin-dependent transport characteristics of Fe met-cars

Using non-equilibrium Green’s function and first-principles calculations we study structural, electronic, and transport properties of Fe₈C₁₂ met-car cluster sandwiched between two Au (1 0 0) electrodes. Several orientations were considered for the cluster attached to the gold surface and full structural optimization has been performed for the whole two-probe system. It was found a large current value for the present device and the molecular orientation plays an important role in the conducting behavior of the system. In energetically favorable case the I–V characteristic remains almost linear at low bias voltage (up to 1.5 V). This finding can be attributed to this fact that the transmission coefficient is almost flat around the gold Fermi level since the transmission is dominated by several broad molecular orbitals. We show that the electronic transmission is significantly spin-polarized while its size is large for the C atoms linkage. We also observe and discuss the NDR behavior of this novel molecular device in the range of 1.0–1.5 V for the energetically favorable configuration. The results are rationalized by analyzing the device transmission coefficient and density of states spectra.     

A molecular modeling study on full-length insulin: insight into initial events of amyloid formation

Studies on the structure and physico-chemical properties of amyloid fibrils are important with regard to a better understanding of amyloid diseases such as Alzheimer’s. Insulin is used as a protein model which is easily driven toward amyloid formation. In the present study, five sets of 15 ns molecular dynamics simulations were performed on insulin in order to observe the initial structural changes that occur in the process of amyloid formation. Potential energy, RMSD, and secondary structure percentage of sampled structures were analyzed in all experiments. Common residues that undergo the first conformational changes were detected to be S9 and V10 of the A chain, as well as G8 and S9 of the B chain. The RMSD of truncated insulin increased much more than full-length insulin to about 18 Å. However, the beta-sheet structures percentage of full-length insulin, which is an indicative of amyloid formation, was higher than the truncated form in the presence of salt. This is indicative of the importance of the five residues of the B chain C-terminal in the insulin misfolding process. Overall, simulating full-length insulin under high temperature and in the presence of KCl could be used to assess amyloid formation and potential amyloid inhibitors of this protein.     

Molecular structure and bonding character of mono and divalent metal cations (Li+, Na+, K+, Be2+, Mg2+, and Ca2+) with substituted benzene derivatives: AIM,NBO, and NMR analyses

Cation–π complexes between several cations (Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, and Ca²⁺) and different π-systems such as para-substituted (F, Cl, OH, SH, CH₃, and NH₂) benzene derivatives have been investigated by UB3LYP method using 6-311++G** basis set in the gas phase and the water solution. The ions have shown cation–π interaction with the aromatic motifs. Vibrational frequencies and physical properties such as dipole moment, chemical potential, and chemical hardness of these compounds have been systematically explored. The natural bond orbital analysis and the Bader’s quantum theory of atoms in molecules are also used to elucidate the interaction characteristics of the investigated complexes. The aromaticity is measured using several well-established indices of aromaticity such as NICS, HOMA, PDI, FLU, and FLUπ. The MEP is given the visual representation of the chemically active sites and comparative reactivity of atoms. Furthermore, the effects of interactions on NMR data have been used to more investigation of the studied compounds.     

Synthesis,structure, and electrochemistry of pyridinecarboxamide cobalt(III) complexes; the effect of bridge substituents on the redox properties

Two series of complexes of the types trans-[Co^III(Mebpb)(amine)₂]ClO₄ {Mebpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-methylbenzene dianion, and amine = pyrrolidine (prldn) (1a), piperidine (pprdn) (2a), morpholine (mrpln) (3a), benzylamine (bzlan) (4a)}, and trans-[Co^III(cbpb)(amine)₂]X {cbpb²⁻ = N,N-bis(pyridine-2-carboxamido)-4-chlorobenzene dianion, and amine = pyrrolidine (prldn), X = PF₆ (1b), piperidine (pprdn), X = PF₆ (2b), morpholine (mrpln), X = ClO₄ (3b), benzylamine (bzlan), X = PF₆ (4b)} have been synthesized and characterized by elemental analyses, IR, UV–Vis, and ¹H NMR spectroscopy. The crystal structure of 1a has been determined by X-ray diffraction. The electrochemical behavior of these complexes, with the goal of evaluating the effect of axial ligation and equatorial substitution on the redox properties, is also reported. The reduction potential of Co^III, ranging from −0.53 V for (1a) to −0.31 V for (3a) and from −0.48 V for (1b) to −0.22 V for (3b) show a relatively good correlation with the σ-donor ability of the axial ligands. The methyl and chloro substituents of the equatorial ligand have a considerable effect on the redox potentials of the central cobalt ion and the ligand-centered redox processes.     

Identifying the Interfacial Polarization in Non-stoichiometric Lead-Free Perovskites by Defect Engineering

Recent advances in perovskite ferroelectrics have fostered a host of exciting sensors and actuators. Defect engineering provides critical control of the performance of ferroelectric materials, especially lead-free ones. However, it remains a challenge to quantitatively study the concentration of defects due to the complexity of measurement techniques. Here, a feasible approach to analyzing the A-site defect and electron in alkali metal niobate is demonstrated. The theoretical relationships among defect concentration, conductivity, and oxygen partial pressure can be established based on the defect chemistry equilibria. The type and concentration of defects are reflected through the conductivity variation with oxygen partial pressure. As a result, the variation of defect concentration gives rise to defect-driven interfacial polarization, which further leads to distinct properties of the ceramics. e.g., abnormal dielectric behavior. Furthermore, this study also suggests a strategy to manipulate defects and charges in perovskite oxides for performance optimization.     

Crystal structures and in vitro anticancer studies on new unsymmetrical copper(II) Schiff base complexes derived from meso-1,2-diphenyl-1,2-ethylenediamine: a comparison with related symmetrical ones

Two new unsymmetrical copper(II) Schiff base complexes, [CuLⁿ(py)]ClO₄ (n = 1, 2) in which Lⁿ represents a tridentate N₂O type Schiff base ligand, were synthesized. Lⁿs were derived from monocondensation of meso-1,2-diphenyl-1,2-ethylenediamine with salicylaldehyde or 3-methoxysalicylaldehyde. The reaction between [CuLⁿ(py)]ClO₄ and other salicylaldehyde derivatives resulted in new N₂O₂ unsymmetrical tetradentate Cu^II complexes, CuL^3–6. Crystal structures of [CuL¹(py)]ClO₄, CuL⁴, and CuL⁵ were obtained. These new complexes as well as a series of related symmetrical ones (i.e. CuL^7–12) were tested for their in vitro anticancer activity against human liver cancer cell line (Hep-G2) by MTT and apoptosis assay. All of the complexes showed considerable cytotoxic activity against tumor cell lines (IC₅₀ = 5.13–16.24 μg mL^?1). The symmetrical CuL⁷ was the most potent anticancer derivative (IC₅₀ = 5.13 μg mL^?1) compared to the control drug 5-FU (IC₅₀ = 5.4 μg mL^-1, p < 0.05). Flow cytometry experiments showed that the copper derivatives especially [CuL²(py)]ClO₄ and CuL⁷ induced more apoptosis on Hep-G2 tumor cell lines compared to 5-FU.     

Cold atmospheric plasma modification of curcumin loaded in tri‐phosphate chitosan nanoparticles enhanced breast cancer cells apoptosis

The anti‐cancer mechanisms of curcumin have been reported to include suppressions of angiogenesis and tumor proliferation. The main goal of this research is to increase the solubility of curcumin by cold atmospheric plasma (CAP) and assess the effects of modified curcumin by charging with tri‐polyphosphate chitosan nanoparticles for MCF‐7, MDA‐MB‐231 breast cancer cells, and human fibroblast cells. Curcumin modification was done by CAP and its solubility was evaluated by spectrophotometry. After loading modified curcumin into nano‐chitosan‐TPP, nanocurcumin was characterized by scanning electron microscopy. Cellular viability and apoptosis of treated cells were assessed by MTT and Annexin V. The changes of messenger RNA expression of TP5353 and VEGF genes were analyzed by real‐time PCR. CAP was able to transform the curcumin to possess hydrophilic characteristics after 90 seconds. The mean diameter of Curcumin loaded chitosannanoparticles (NPs) were determined as 48 nm. MTT results showed that the IC₅₀ of nano Cur‐chitosan‐TPP was effectively decreased compared to free curcumin in MCF‐7 (15 μg/mL at 72 hours vs 20 μg/mL at 48 hours). Additionally, nano Cur‐chitosan‐TPP had no significant effect on normal cells (Human dermal fibroblas: HDF), whereas it also decreased the viability of triple negative breast cancer cell line (MDA‐MB‐231). Real‐time PCR results showed that expression level of TP53 gene was upregulated (P = .000), whereas VEGF gene downregulated (P = .000) in treated MCF‐7 cells. Curcumin loaded chitosan nanoparticles have led to an induction of apoptosis (79.93%) and cell cycle arrest (at S and G2M). Modified‐curcumin‐tri‐polyphosphate chitosan nanoparticles using CAP can be considered as a proper candidate for breast cancer treatment.     

Synthesis and Characterization of Tricarbastannatranes and Their Reactivity in B(C6F5)3‐Promoted Conjugate Additions

The synthesis and characterization of a series of tricarbastannatranes, in the solid state and in solution, are described. The structures of the complexes [N(CH₂CH₂CH₂)₃Sn](BF₄), [N(CH₂CH₂CH₂)₃Sn](SbF₆), [N(CH₂CH₂CH₂)₃Sn]₄[(SbF₆)₃Cl], and [(N(CH₂CH₂CH₂)₃Sn)₂OH][MeB(C₆F₅)₃] were determined by X‐ray crystallography. Furthermore, the B(C₆F₅)₃‐promoted conjugate addition of alkyl‐tricarbastannatranes to benzylidene derivatives of Meldrum’s acid was investigated, and detailed mechanistic studies are presented.