Characterization and analytical application of surface modified magnetic nanoparticles

Fe₃O₄ superparamagnetic nanoparticles with various functionalities were synthesized using a chemical co-precipitation method and used to demonstrate their analytical applications for protein separation of protein and metal ion extraction. The chemically inert silica layer coated with tetraethoxysilane (TEOS) protected the Fe₃O₄ core from a chemical attack and allowed the nanoparticles to be well dispersed in an aqueous solution. Particularly, the beads were resistant to an acidic solution with a pH ≥ 3. The amino (− NH₂) groups were covalently bonded to the silica coated Fe₃O₄, and then the carboxyl (− COOH) groups were functionalized to the nanoparticle surface through the reaction of − NH₂ and glutaric anhydride. The synthesized magnetic nanoparticles (MNP) were characterized using FT-IR, FE-TEM, XRD, and SQUID. The presence of functional groups on the nano beads was confirmed using molecular fluorescence spectrometry. For the presence of the amino (− NH₂) groups, FITC was tagged and monitored using an excitation laser with a wavelength of 473 nm and a fluorescence emission of 518 nm. Biotin was immobilized on the MNP and the fluorescent of FITC tagged on avidin was monitored to identify the carboxyl (− COOH) group.The proteins of Cytochrome C (12,000 Da), Rnase B (15,000 Da), and Myoglobin (17,000 Da) were separated using the MNP functionalized with the carboxyl (− COOH) group and identified using MALDI-TOF-MS. Amino benzyl EDTA (ethylenediaminetetraacetic acid) was immobilized on the MNP for metal–EDTA complexation to use the synthesized magnetic particles to extract metal ions for environmental and clinical application. Cu, Cd, Co, and Pb ions were extracted from ∼ 10 ng/mL solutions in the batch-type procedure and the extraction efficiency was > 90% at a pH of 4.     

Nucleophilicity and accessibility calculations of alkanolamines: applications to carbon dioxide absorption reactions

Both nucleophilicities and accessibilities of three alkanolamines [monoethanolamine (MEA), (2-(methylamino)ethanol (MAE), and 2-amino-2-methyl-1-propanol (AMP)] were calculated to predict their reactivities with CO(2). After DFT geometry-optimization calculations, the global, group, and atomic nucleophilicities of each amine were obtained using MP2 quantum mechanical calculations. Only global nucleophilicity matched an experimental pK(a) order (MAE > AMP > MEA). However, it failed to predict the slow rate of the sterically hindered AMP and the order of rate constants, MAE > MEA > AMP. The accessibilities of amines to CO(2) have been calculated by MD simulations by monitoring collisions at the reaction centers: N atoms in amines and C in CO(2). The accessibility results indicate that global nucleophilicity needs quantitative correction for steric effects to predict better reactivities of amines with CO(2).     

Parathyroid hormone accelerates decompensation following left ventricular hypertrophy

Parathyroid hormone (PTH) treatment was previously shown to improve cardiac function after myocardial infarction by enhancing neovascularization and cell survival. In this study, pressure overload-induced left ventricular hypertrophy (LVH) was induced in mice by transverse aortic banding (TAB) for 2 weeks. We subsequently evaluated the effects of a 2-week treatment with PTH or saline on compensated LVH. After another 4 weeks, the hearts of the mice were analyzed by echocardiography, histology, and molecular biology. Echocardiography showed that hearts of the PTH-treated mice have more severe failing phenotypes than the saline-treated mice following TAB with a greater reduction in fractional shortening and left ventricular posterior wall thickness and with a greater increase in left ventricular internal dimension. Increases in the heart weight to body weight ratio and lung weight to body weight ratio following TAB were significantly exacerbated in PTH-treated mice compared to saline-treated mice. Molecular markers for heart failure, fibrosis, and angiogenesis were also altered in accordance with more severe heart failure in the PTH-treated mice compared to the saline-treated mice following TAB. In addition, the PTH-treated hearts were manifested with increased fibrosis accompanied by an enhanced SMAD2 phosphorylation. These data suggest that the PTH treatment may accelerate the process of decompensation of LV, leading to heart failure.     

Effect of water electrolysis catalysts on carbon corrosion in polymer electrolyte membrane fuel cells

A new approach to preventing electrochemical carbon corrosion in the cathode of polymer electrolyte membrane fuel cells (PEMFCs) was developed. The addition of 2 wt % IrO(2) (0.016 mg cm(-2)) to the catalyst layer of the cathode was demonstrated to reduce the electrochemical corrosion of carbon by 76% at 1.6 V(NHE) and 70 °C compared with a commercial Pt/C catalyst of the same Pt loading of 0.4 mg cm(-2) and under the same test conditions. The IrO(2) was shown to behave as a catalyst for water electrolysis, thereby removing water from the catalyst layer, which promoted electrochemical carbon corrosion.     

Guaiane Sesquiterpenoids Isolated from the Fruits of Torilis japonica and Their Cytotoxic Activity

Two new guaiane sesquiterpenoids, 11‐(acetyloxy)‐1,8‐dihydroxyguai‐4‐en‐3‐one ( 5 ) and (1α,6β)‐1,6‐dihydroxytorilin ( 6 ), were isolated from the fruits of Torilis japonica (Umbelliferae), along with four known sesquiterpenes, torilin ( 1 ), torilolone ( 2 ), (1β)‐1‐hydroxytorilin ( 3 ), and (1α)‐1‐hydroxytorilin ( 4 ). During the phytochemical investigation, daucosterol, friedelin, and epifriedelanol were also isolated from the plant for the first time. The structures of the new sesquiterpenoids 5 and 6 were determined by comprehensive analyses of MS and NMR spectroscopic data. These isolates were evaluated against human breast cancer cells (MCF‐7) and Lewis lung carcinoma (LLC) cells. Compounds 1, 3 , and 4 exhibited cytotoxic activity against the LLC cells with IC₅₀ values of 31.3, 32.5, and 34.0 μg/ml, respectively. However, no significant cytotoxicity was found against the MCF‐7 cells for any of the compounds tested.     

Preparation and cycle performance at high temperature for Li[Ni0.5Co0.2Mn0.3]O2 coated with LiFePO4

Li[Ni_0.5Co_0.2Mn_0.3]O₂ coated with LiFePO₄ was synthesized by a co-precipitation method. It consisted of the parent Li[Ni_0.5Co_0.2Mn_0.3]O₂ as the core and the LiFePO₄ as the coating material, with an average particle diameter of 500 nm. The LiFePO₄-coated Li[Ni_0.5Co_0.2Mn_0.3]O₂ showed no large initial capacity drop in the first cycle, which generally occurred with cathode materials bearing inactive coating layers such as Al₂O₃, ZnO, and MgO. Furthermore, it presented a remarkably improved cycle retention rate of over 89% until 400 cycles at 50 °C. We suggest that the LiFePO₄ coating technique is a very effective tool to improve the cycle performance of Li[Ni_0.5Co_0.2Mn_0.3]O₂ at high temperatures.     

A stereo-controlled access to functionalized macrolactams via an aza-Claisen rearrangement

A novel and stereo-controlled method for the preparation of functionalized macrolactams was developed. The process involves stereoselective enol ether formation, followed by an azacyclic ring expansion via an aza-Claisen rearrangement. Herewith, we describe a systematic investigation of an aza-Claisen rearrangement-induced ring expansion of azacycles prepared by appending E/Z-enol ethers to the medium-sized lactams as well as the stereochemical outcome. In addition, the strategy was successfully applied to the total synthesis of fluvirucinine A(1) and 3-epi-fluvirucinine A(1). This method offers an attractive alternative to the intramolecular amide-aldol reaction for the elaboration of β-alkoxy-α-substituted motifs.     

Capacitance-based assay for real-time monitoring of endocytosis and cell viability

Label-free cell-based assays have emerged as a promising means for high-throughput screening. Most label-free sensors are based on impedance measurements that reflect the passive electrical properties of cells. Here we introduce a capacitance-based assay that measures the dielectric constant (capacitance) of biological cells, and demonstrate the feasibility of analyzing endocytosis and screening chemotherapeutic agents with this assay. Endocytosis induces a change in the zeta potential, leading to a change in the dielectric constant which enables real-time endocytosis monitoring using the capacitance sensor. Additionally, since the dielectric constant is proportional to cell radius and cell volume, cell viability can be estimated from the change in capacitance. Therefore, the capacitance sensor array can also be used for cytotoxicity testing for large-scale chemotherapeutic screening.     

Mixed colloidal suspensions of reduced graphene oxide and layered metal oxide nanosheets: useful precursors for the porous nanocomposites and hybrid films of graphene/metal oxide

Homogeneously mixed colloidal suspensions of reduced graphene oxide, or RGO, and layered manganate nanosheets have been synthesized by a simple addition of the exfoliated colloid of RGO into that of layered MnO(2). The obtained mixed colloidal suspensions with the RGO/MnO(2) ratio of ≤0.3 show good colloidal stability without any phase separation and a negatively charged state with a zeta (ζ) potential of -30 to -40?mV. The flocculation of these mixed colloidal suspensions with lithium cations yields porous nanocomposites of Li/RGO-layered MnO(2) with high electrochemical activity and a markedly expanded surface area of around 70-100?m(2) g(-1). Relative to the Li/RGO and Li/layered MnO(2) nanocomposites (≈116 and ≈167?F?g(-1)), the obtained Li/RGO-layered MnO(2) nanocomposites deliver a larger capacitance of approximately 210?F?g(-1) with good cyclability of around 95-97?% up to the 1000th cycle, thus indicating the positive effect of hybridization on the electrode performances of RGO and lithium manganate. Also, an electrophoretic deposition of the mixed colloidal suspensions makes it possible to easily fabricate uniform hybrid films composed of graphene and manganese oxide. The obtained films show a distinct electrochemical activity and a homogeneous distribution of RGO and MnO(2). The present experimental findings clearly demonstrate that the utilization of the mixed colloidal suspensions as precursors provides a facile and universal methodology to synthesize various types of graphene/metal oxide hybrid materials.     

N719 dye-sensitized organophotocatalysis: enantioselective tandem Michael addition/oxyamination of aldehydes

A remarkably efficient photosensitizer, N719 dye, was used in asymmetric tandem Michael addition/oxyamination of aldehydes, rendering α,β-substituted aldehydes in good yields with excellent levels of enantioselectivity and diastereoselectivity. This is the first report of a multiorganocatalytic reaction involving iminium catalysis and photoinduced singly occupied molecular orbital (SOMO) catalysis. This reaction is expected to expand the scope of tandem organocatalytic reactions.