Micro-Determination of Protein Containing SH– and –S–S– Groups Based on the Polarographic wave of an Electroactive Derivative

This paper presents a new simple and sensitive method for the micro-determination of protein containing SH– and –S–S– groups based on the single sweep polarographic wave of an electroactive derivative. In 0.04molL^–1 Na₃PO₄ and 0.2% ascorbic acid solution, protein is heated in a boiling water bath for 15min, the reaction product giving a sensitive reduction wave at –0.70V (vs. SCE). The wave height is linearly proportional to the concentration of protein. The calibration curves of bovine serum albumin (BSA), human serum albumin (HSA), ovalbumin (OVA) and lysozyme (Lyso) are constructed under the optimal conditions. For BSA and HSA, the linear ranges and detection limits are 0.05–24mgL^–1 and 0.02mgL^–1, respectively. The method has been applied to the determination of protein in human serum samples with satisfactory results. The mechanism of the polarographic wave was also studied, and the results show that S^2– ion is released from the protein molecule during the derivatization reaction, the wave being attributed to the reduction of HgS.     

Ruthenium hydrazone complexes with 1:1 and 1:2 metal–ligand stoichiometry: a comparison of biomolecular interactions and in vitro cytotoxicities

Transition Metal Chemistry - Two ruthenium(II) complexes [RuIICl(PPh3)2(L)] (1) and [RuII(L)2] (2) were synthesized by reacting [RuCl2(PPh3)3] and thiophene-2-carboxylic acid...     

Four-membered ring cyclic ketene –O,O–, –O,S–, –O,N–, –S,S–, –S,N–, and –N,N–acetals and their corresponding cations: a computational study

A systematic computational study of four-membered cyclic ketene –O,O–, –O,S–, –O,N–, –S,N– and –N,N-acetals as well as their protonated analogs have been performed at the second order M?ller Plesset level with a polarized triple zeta basis set. The main purpose of this study was to make predictions about the nucleophilicity of these systems and the variations in nucleophilicity with the hetero atoms. Our calculations suggest that all six target molecules are good nucleophiles, and that the N,N analog is the strongest and the S,S analog the weakest nucleophile. Our results include molecular geometries, bond lengths, proton affinities, vibrational frequencies, and calculated charges.     

Synthesis of histidinoalanine: a comparison of β-lactone and sulfamidate electrophiles

Previous syntheses of histidinoalanine (HAL) have led to mixtures of regioisomers and/or stereoisomers. For example, opening of N-Cbz-D-serine-β-lactone (6) with Boc-L-His-OMe (5) gave a 2:1 mixture of τ- and π-regioisomers. The sulfamidate 10, derived from N-benzyl-D-serine methyl ester (11), was reacted with Boc-L-His-OMe (5) to give the τ-HAL derivative 17 as a single isomer in 57% yield. A similarly prepared τ-HAL 19, bearing protecting groups that were all hydrogenolytically labile, led to the free bis-amino acid, τ-L-histidinyl-D-alanine (τ-4), as a salt-free standard for amino acid analysis.     

Sensitivity comparison of gas chromatography–mass spectrometry with Cold EI and standard EI

Gas chromatography–mass spectrometry (GC–MS) with Cold EI is based on interfacing GC and MS with supersonic molecular beams (SMBs) along with electron ionization of vibrationally cold sample compounds in SMB in a fly-through ion source (hence the name Cold EI). Cold EI improves all the central performance aspects of GC–MS, and in this paper, we focus on its improvement of signal-to-noise ratio (S/N) and limits of detection (LODs). We found that the harder the compound for analysis with standard EI, the greater the Cold EI gain in S/N and LOD. The lower LOD and higher S/N of Cold EI emerge from a few reasons: (a) similar ionization yield as standard EI, (b) enhanced abundance of molecular ions, (c) elimination of vacuum background noise, (d) elimination of ion source-related peak tailing and degradation, (e) ability to lower the elution temperatures via the use of high column flow rates, and (f) greater range of thermally labile and low-volatility compounds that can be analyzed. We demonstrate the superior S/N and lower LOD of Cold EI versus standard EI in a range of compounds, from the simple-to-analyze octafluoronaphthalene all the way to reserpine and an organo-metallic compound that cannot be analyzed by standard EI. These compounds include methyl stearate, cholesterol, n-C₃₂H₆₆, large polycyclic aromatic hydrocarbons, dioctyl phthalates, diundecyl phthalate, pentachlorophenol, benzidine, lambda-cyhalothrin, and methidathion. The significantly lower Cold EI LODs that can be over 1000 times better than in standard EI further result in far superior response linearity and greater measurement dynamic range.     

B−B Cleavage and Ring-Expansion of a 1,4,2,3-Diazadiborinine with N-Heterocyclic Carbenes

A 1,4,2,3-diazadiborinine derivative was found to form Lewis adducts with strong two-electron donors such as N-heterocyclic and cyclic (alkyl)(amino)carbenes. Depending on the donor, some of these Lewis pairs are thermally unstable, converting to sole B,N-embedded products upon gentle heating. The products of these reactions, which have been fully characterized by NMR spectroscopy, elemental analysis, and single-crystal X-ray diffraction, were identified as B,N-heterocycles with fused 1,5,2,4-diazadiborepine and 1,4,2-diazaborinine rings. Computational modelling of the reaction mechanism provides insight into the formation of these unique structures, suggesting that a series of B−H, C−N, and B−B bond activation steps are responsible for these “intercalation” reactions between the 1,4,2,3-diazadiborinine and NHCs.     

Synthesis of cellulose–metal nanoparticle composites: development and comparison of different protocols

Deposition of nanoparticles on the surface of a variety of materials is a subject of great interest due to their potential applications in electronic devices, sensing, catalysis and bio-medical sciences. In this context, we have explored and compared various methodologies to generate gold and silver nanoparticles on the surface of cellulose fibers. It was found that boiling of the cellulose fibers in alkaline solution of gold and silver salts led to the formation and immobilization of gold and silver nanoparticles. However, in case of lecithin treated and thiol-modified cellulose fibers, high temperature was not essentially required for the formation and deposition of nanoparticles on cellulose substrate. In both these cases, fairly uniform metal nanoparticles were obtained in good yields (~43 wt% gold loading in case of thiol modified cellulose fibers) at room temperature. Borohydride-reduction method resulted in relatively lower loading (~22 wt%) with a wide size distribution of gold and silver nanoparticles on cellulose fibers. All these nanoparticle–cellulose composites were thoroughly characterized using scanning electron microscopy, energy dispersive X-ray, Fourier transform infrared spectroscopy, UV–visible spectroscopy, and elemental analyzer. Thiol modified cellulose–gold nanoparticle composites served as active catalysts in the reduction of 4-nitrophenol into 4-aminophenol.     

Phase transition temperatures of Sn–Zn–Al system and their comparison with calculated phase diagrams

The Sn?CZn?CAl system was studied in connection with the possible substitution of lead-based solders for temperatures up to 350?°C. Ternary alloys with up to 3?wt% of aluminium were prepared. The investigated alloys lie close to the monovariant line (eutectic valley) of the Sn?CZn?CAl system. The temperatures of phase transitions of six binary Sn?CZn reference alloys and fourteen ternary Sn?CZn?CAl alloys using DTA method were investigated in this paper. DTA experiments were performed at the heating/cooling rate of?4?°C?min^?1 using Setaram SETSYS 18_TM experimental equipment. The temperatures of phase transitions in the ternary Sn?CZn?CAl system were obtained, namely, the temperature of ternary eutectic reaction T _E1 (197.7?±?0.7?°C), temperature of ternary transition reaction T _U1 (278.6?±?0.7?°C), temperatures of liquidus and other transition temperatures for studied alloys. Temperatures obtained during DTA heating runs were used as authoritative. DTA curves obtained during cooling enabled realising better differentiation of the obtained overlapped heat effects (peaks) during heating. Theoretical isopleths of the Sn?CZn?CAl phase diagram were calculated using the Thermocalc software and MP0602 thermodynamic database. Experimental data were compared with the calculated temperatures, and a good agreement was obtained.     

Nanoscale cooperativity on a series of statistical methacrylates copolymers with electron donor–acceptor pendant groups

Standard and StepScan DSC studies have been performed on a series of statistical methacrylate copolymers with electron-donor and electron-acceptor pendant groups that form intramolecular electron transfers. From standard DSC analysis we concluded that glass transition temperature slowly increased with increasing electron-acceptor monomeric moiety ratio up to 0.5 in the main chain. Using StepScan DSC method we calculated the size and volume of cooperative rearranging region as well mean temperature fluctuation at glass transition temperature. It was estimated also the average number of monomer units in the cooperative rearranging region. All parameters were calculated according to the method proposed by Donth based on Heat Capacity Spectroscopy. The results show that the presence of intermonomeric electron transfers decreased the chain mobility, as well as the cooperativity of relaxation processes of these structures in the glass transition range. This is reflected by minimal values of these parameters around 0.4 ratio of copolymer composition. Such behavior is similar to that of crosslinked or confined systems (e.g., nanocomposites, thin films) that have reduced chain mobility.     

Host–guest complexation of a nitroheterocyclic compound with cyclodextrins: a spectrofluorimetric and molecular modeling study

Nitroheterocyclic compounds (NC) were candidate drugs proposed for Chagas disease chemotherapy. In this study, we investigated the complexation of hydroxymethylnitrofurazone (NFOH), a potential antichagasic compound, with α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), Hydroxypropyl-β-cyclodextrin (HP-β-CD), Dimethyl-β-cyclodextrin (DM-β-CD) and γ-cyclodextrin (γ-CD) by fluorescence spectroscopy and molecular modeling studies. Hildebrand–Benesi equation was used to calculate the formation constants of NFOH with cyclodextrins based on the fluorescence differences in the CDs solution. The complexing capacity of NFOH with different CDs was compared through the results of association constant according to the following order: DM-β-CD > β-CD > α-CD > HP-β-CD > γ-CD. Molecular modeling studies give support for the experimental assignments, in favor of the formation of an inclusion complex between cyclodextrins with NFOH. This is an important study to investigate the effects of different kinds of cyclodextrins on the inclusion complex formation with NFOH and to better characterize a potential formulations to be used as therapeutic options for the oral treatment of Chagas disease.     

Aromaticity and π-bond covalency: prominent intermolecular covalent bonding interaction of a Kekulé hydrocarbon with very significant singlet biradical character

An anthracene-linked bisphenalenyl Kekulé molecule with very significant singlet biradical character has shown a prominent covalent bonding interaction between molecules in a molecular aggregate. High aromatic stabilization energy in the anthracene linker is responsible for the significant singlet biradical character.     

Development of a detailed pyrolysis mechanism for C1–C4 hydrocarbons under a wide range of temperature and pressure

A model of core mechanism of hydrocarbon pyrolysis with good predictive ability is crucial to the development of active cooling technology for advanced aeroengines. In this work, a detailed core kinetic model of pyrolysis of C₁–C₄ hydrocarbon fuels is developed through the combination of a series of potential energy surfaces and validated against a series of experimental results. The kinetic model contains 103 species and 1290 reactions, and most of the kinetic and thermochemical parameters are compiled from recent highly accurate quantum chemical calculations without modification. The pressure-dependent rate constants are considered for the dissociation/association reactions, isomerization reactions, and chemically activated reactions. Simulation results for various alkanes (methane, ethane, propane, n-butane, isobutane), alkenes (ethylene, propene, 1-butene, 2-butene, isobutene, allene, 1,3-butadiene), and alkynes (acetylene, propyne, vinylacetylene) indicate that the major product distributions at various temperatures (800-2300 K) and pressures (0.8-10 atm) can be predicted well by the developed core kinetic model. Thus, the developed pyrolysis mechanism for C₁–C₄ hydrocarbons can be used as a cornerstone to develop the pyrolysis mechanisms of larger hydrocarbon fuels and thus support the development of thermal management in advanced aeroengines.     

Synthesis of a benzoxazine monomer containing maleimide and allyloxy groups

A novel benzoxazine monomer 3-（4-allyloxy）phenyl-3,4-dihydro-2H-6-（N-maleimido）-l,3-benzoxazine （AMB） was synthesized and structure was confirmed by FT-IR, 1H NMR. Thermal analysis （DSC） of AMB showed the introduction of allyloxy group melting point and exhibited a narrow and symmetric curing exothermic window.     

CMMSE: analysis and comparison of some numerical methods to solve a nonlinear fractional Gross–Pitaevskii system

Journal of Mathematical Chemistry - In this work, we introduce and theoretically analyze various computational techniques to approximate the solutions of solve a fractional extension of a double...     

Preparing undoped and Mn-doped ZnO nanoparticles: a comparison between sol–gel and gel-combustion methods

Undoped and Mn doped ZnO nanoparticles were synthesized by two wet chemical techniques: sol–gel and gel-combustion. We were able to prepare Mn-doped ZnO nanoparticles free from the second phases at calcining temperatures 400 and 500 °C using sol–gel and gel combustion, respectively. Complete crystallization occurs in both methods, but it is found that the crystallization is better performed in the ZnO based solid solution prepared by the sol–gel method. TEM images show that the average size of the nanoparticles synthesized by gel-combustion is smaller than that of prepared by sol–gel method. Optical characterizations such as vibrational properties, lattice dynamical parameters, absorption edges and optical band gap energies were also carried out by FTIR and UV–Vis spectroscopies. The quantitative estimations led to the conclusion that the effects of the method on the particle size and the optical band gap energy of the prepared samples are very significant.     

Synthesis and characterization of a dipeptide–copper(II)– 2-aminomethylbenzimidazole ternary complex

A new ternary complex [Cu(glygly)(AMBZ)(H₂O)]Cl·H₂O (1) (glygly?=?glycylglycine anion, AMBZ?= 2-aminomethylbenzimidazole) has been prepared and characterized by single-crystal X-ray diffractometry and ESR, electronic and IR spectroscopy. The copper(II) ion has a slightly distorted square-pyramidal coordination, being equatorially coordinated by the bidentate 2-aminomethylbenzimidazole and the bidentate glycylglycine anion and axially by a water molecule. The individual complex molecules are hydrogen bonded to their neighbors, forming a polymeric hydrogen-bonded lattice. Spectroscopic data are in accordance with the crystal structure.     

Electrochromic and spectroelectrochemical properties of polythiophene β-substituted with alkyl and alkoxy groups

Journal of Solid State Electrochemistry - Polythiophenes are conjugated polymers that are highly promising candidates for use as an active layer in flexible optoelectronic devices. The...     

Azo-functionalised achiral bent-core liquid crystalline materials: effect of presence of –N=N– linkage at different locations in the molecular architecture

Here, we report four new homologous series of azo-functionalised achiral bent-core compounds. The paper deals with the design, synthesis and liquid crystalline properties of four new homologous series of photochromic materials. In this study, we have investigated the effect of the presence of –N=N– linkage at different locations of the molecular architecture, on the mesomorphic properties. The molecular structures of all the newly synthesised compounds are established using the organic spectroscopic methods. The liquid crystalline properties are investigated using polarising optical microscopy (POM), differential scanning calorimetry (DSC), X-ray diffraction and electro-optical studies. They exhibit B₁ (col_r) and B₂ (SmC_AP_A) mesophases. We find that the presence of the –N=N– linkage at different locations in the molecular architecture does not seem to have much effect on the mesogenic behaviour of such compounds. However, we clearly see a profound effect of the location of the –N=N– linkage on the photo-induced electro-optical properties of these compounds.     

Synthesis of a conjugate of 3´-sialyllactoside with recombinant flagellin as a carrier protein and assessment of its immunological activity in comparison with that of a similar hemocyanin-based conjugate

In the framework of a project directed to the design of synthetic cancer vaccines based on carbohydrate chains of tumor-associated gangliosides, a new prototype cancer vaccine, a polyvalent carbohydrate-protein conjugate 1 with ～11 3´-sialyllactoside ligands conjugated to one molecule of recombinant flagellin was synthesized. Dendritic cell vaccines were designed using the conjugate 1 and a neoglycoconjugate 2 consisting of ～400 3´-sialyllactose residues linked to hemocyanin from a snail Megathura crenulata (KLH). Comparative ELISA study was conducted to assess the induction of carbohydrate-specific immunoglobulins IgM and IgG after immunization of mice with conjugates 1 and 2 and dendritic cells loaded with 1 and 2. Synthetic polyacrylamide carrier conjugated to 3´-sialyllactose ligands and B16F0 melanoma cells were used as coating antigens.