The preparation of functionalized single walled carbon nanotubes as high efficiency DNA carriers

The positively charged single walled carbon nanotubes (SWNTs~ ) were prepared by conjugating with-CONH-C_6H_(12)-NH_3~ . The double strand DNA(dsDNA) chains were loaded onto SWNTs~ via the electrostatic interactions.SWNTs~ shows improved loading efficiency (353.5μg/mg) toward dsDNA compared with that of charged free single walled carbon nanotubes (SWNTs) (82.9μg/mg).     

The predictive accuracy for estimating infinite dilution activity coefficients by γ∞-based UNIFAC

The predictive accuracy for estimating infinite dilution activity coefficients by a modification of the UNIFAC method wherein the group interaction parameters were based on only data (referred to as -based UNIFAC) has been studied. Estimates and measured values were compared for six prototypical solutes in a series of homologous n-alkanes, l-alcohols and alkanenitrile solvents. Despite the fact that the interaction parameters were derived using only data, this approach still gave serious errors due to several inherent problems in the original UNIFAC model. Its performance is sometimes even poorer than that of the original UNIFAC method. For example for nitromethane in alcohols and p-dioxane in nitriles values predicted by the -based UNIFAC are essentially zero. The large errors for these systems are most likely due to inaccurate interaction parameters in the -based UNIFAC method.     

Receptor-based 3D QSAR analysis of estrogen receptor ligands – merging the accuracy of receptor-based alignments with the computational efficiency of ligand-based methods

One of the major challenges in computational approaches to drug design is the accurate prediction of binding affinity of biomolecules. In the present study several prediction methods for a published set of estrogen receptor ligands are investigated and compared. The binding modes of 30 ligands were determined using the docking program AutoDock and were compared with available X-ray structures of estrogen receptor-ligand complexes. On the basis of the docking results an interaction energy-based model, which uses the information of the whole ligand-receptor complex, was generated. Several parameters were modified in order to analyze their influence onto the correlation between binding affinities and calculated ligand-receptor interaction energies. The highest correlation coefficient (r ² = 0.617, q ² _LOO = 0.570) was obtained considering protein flexibility during the interaction energy evaluation. The second prediction method uses a combination of receptor-based and 3D quantitative structure-activity relationships (3D QSAR) methods. The ligand alignment obtained from the docking simulations was taken as basis for a comparative field analysis applying the GRID/GOLPE program. Using the interaction field derived with a water probe and applying the smart region definition (SRD) variable selection, a significant and robust model was obtained (r ² = 0.991, q ² _LOO = 0.921). The predictive ability of the established model was further evaluated by using a test set of six additional compounds. The comparison with the generated interaction energy-based model and with a traditional CoMFA model obtained using a ligand-based alignment (r ² = 0.951, q ² _LOO = 0.796) indicates that the combination of receptor-based and 3D QSAR methods is able to improve the quality of the underlying model.     

Simple synthesis of sandwich-like SnSe2/rGO as high initial coulombic efficiency and high stability anode for sodium-ion batteries

Metal selenides owing to their high theoretical capacity and good conductivity are considered as one of the potential candidates for the anode materials of sodium-ion batteries(SIBs).However,their practical applications are greatly restricted by the poor cycling performances and complicated synthesis methods.In this work,a sandwich-like Sn Se2/reduced graphene oxide(r GO)composite with a small amount of r GO(7.3%)is synthesized by a simple one-pot solvothermal technique.The as-synthesized Sn Se2/r GO shows improved initial coulombic efficiency(ICE)of 73.7%,high capacity of 402.0 m Ah g-1 after 150 cycles at 0.1 A g-1 with a retention of 86.2%and outstanding rate performances.The abundant Sn-O-C bonds of synthesized material not only accelerate the charge transfer at the interface but also enhance the mechanical strength to accommodate volume variation and prevent active material loss during cycling.Moreover,the compact structure leads to thin solid electrolyte interface(SEI)so that high initial coulombic efficiency was obtained.Furthermore,full cells are assembled to test its potential application.This work offers a simple method to synthesize Sn Se2/r GO as a candidate anode for SIBs.     

DFT study of the conductance of molecular wire:The effect of coupling geometry and intermolecular interaction on the transport properties

The density functional theory (DFT) combining with the non-equilibrium Green functions (NEGF) method is applied to the study of the electronic transport properties for a Di-thiol-benzene (DTB) molecule coupled to two Au(111) surfaces. The dependence of the transport properties on the bias, the coupling geometry of the molecule-electrode interface, and the intermolecular interaction are examined in detail. The results show that the existence of the hydrogen atom at the end of the DTB molecule would significantly decrease the transmission coefficients, and then the differential conductance (dI/dV). By changing the position of the DTB molecule located between two electrodes a maximum value of calculated current is observed. It is also found that the intermolecular interaction will strongly influence the transport properties of the system studied.     

The physicochemical properties and solubility of pharmaceuticals – Methyl xanthines

The aim of this study was to evaluate the physio-chemical properties and solubility of three pharmaceuticals (Phs): theophylline, 7-(β-hydroxyethyl) theophylline, and theobromine in binary systems in different solvents. The solvents used were water, ethanol, and 1-octanol. Score of the solubility of these substances is being important for their dissolution effect inside the cell, the transportation by body fluids and the penetration possibility of lipid membranes.The Phs were classified to the group of methyl xanthines, which contain purine in their structure. Although they are mainly obtained via chemical synthesis, they can be also found in natural ingredients such as cocoa beans and tea leaves. These drugs are mainly acting on the central nervous system but are also used in the treatment of asthma or blood vessels.Solubility of 7 (β-hydroxyethyl) theophylline and theophylline were tested using synthetic method. In case of theobromine, which solubility is very small in the solvents noted, the spectrophotometric method has been used to measure its solubility. After designating phase diagrams of each of the solubility in the bipolar system, the experimental points have been correlated with the equations: Wilson, NRTL, UNIQUAC. Results show that theophylline and its derivatives show the best solubility from all tested Phs.Another method also used during this study was the differential scanning calorimetry (DSC), which allowed designation of the thermal properties of Phs. The fusion temperature and the enthalpy of melting were measured. Unfortunately, it was not possible to determine the fusion temperature and enthalpy of melting of theobromine, because of the decomposition of Ph at high temperature.The important property tested was the constant acidity, to this end, the spectrophotometric method of Bates–Schwarzenbach was used. Unfortunately, with this method it was not possible to determine the value of pK_a 7-(β-hydroxyethyl) theophylline. For other Phs, these values do not differ significantly from those proposed in the literature.Both awareness and knowledge of values of the drug pK_a and solubility are important in Phs production. This allows the selection of a suitable solvent and allows estimation of the correct dose and its capacity to absorb in human body.     

Dimethylmalonoyl peroxide – the neglected lowest homologue: simple synthesis and high reactivity

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The use of composition and high pressure to extend the range of α-quartz isotypes

The use of high pressure and the inclusion of elements such as boron, nitrogen and fluorine increase the number of compounds that adopt the α-quartz-type structure. The α-quartz-type forms of boron phosphate (BPO₄), phosphorus oxynitride (PON) and representatives of the continuous solid solution between silica and phosphorus oxynitride, including the nearly stoichiometric material SiPO₃N, were prepared under high-pressure, high-temperature conditions. The crystal structures of BPO₄ and PON were refined using X-ray and neutron powder diffraction data, respectively. The intertetrahedral A-X-A′ bridging angles of 140.1° and 140.6°, respectively, are slightly lower than in α-quartz as would be expected based on the higher densities of these materials. Preliminary refinements using the X-ray data from the SiO₂-PON solid solutions provide no indication of Si/P order and yield fractional atomic coordinates that are very similar to those observed for the pure end members. These results indicate that one may continuously tune the unit cell and structural parameters by varying the composition of this solid solution. Other compounds, which adopt or may adopt α-quartz-type structures, are also discussed. The present work indicates that the known relationship between the intertetrahedral A-X-A′ bridging angle and the density in α-quartz-type materials also applies to boron compounds, oxynitrides and fluorides. This use of the variables composition and pressure enables structure-property relationships for α-quartz isotypes to be extended and increases the number of potential candidates for piezoelectric materials.     

Electronic and vibrational spectra of tourmaline – The impact of electron beam irradiation and heat treatment

Irradiation and heat treatment were performed on tourmalines of various colors from Antandrokomby, Madagascar. The samples were irradiated with 10 MeV electrons to fluencies of 2 ×10¹⁷ cm⁻² for 1 h and were heated at 550 °C for 3 h in air. Their electronic and vibrational spectra were investigated by UV–vis, mid-infrared, and WD-XRF spectroscopy for comparison to pristine samples. Changes in the Mn³⁺ ions after irradiation resulted in darker pink tourmalines, which had absorption peaks at 390 and 520 nm. These samples became colorless after subsequent heat treatment. After irradiation, colorless, light blue and yellow tourmalines displayed a new absorption band at 365 nm. Alteration of the stretching absorption bands and wavenumber after irradiation could be explained by the following reactions:OH⁻ + e⁻ beam irradiation → O⁻ + H°,Mn²⁺ + e⁻ beam irradiation → Mn³⁺ + e⁻ andFe²⁺ + e⁻ beam irradiation → Fe³⁺ + e⁻.Stretching vibration of the BO₃ structure occurred at 1330 cm⁻¹, while the SiO vibration absorption bands were assigned to around 1100 cm⁻¹. Colorless, green, and yellow tourmalines showed high-intensity peaks around 3608 and 3505 cm⁻¹ after irradiation. Pink and dark green tourmalines showed low-intensity peaks at 3605 and 3585 cm⁻¹, respectively. The combination modes of stretching and bending in the range of 4600–4300 cm⁻¹ were split after irradiation and heat treatment, and different color changes occurred after irradiation.     

Analysis of ochratoxin A in grapes,musts and wines by LC–MS/MS: First comparison of stable isotope dilution assay and diastereomeric dilution assay methods

Ochratoxin A (OTA) exhibits potent nephrotoxic, carcinogenic and teratogenic effects and its maximum level in wines has been set to 2 μg L⁻¹ by regulation. Consequently, the analytical procedures for OTA determination in wines have to be both very sensitive and reliable. In this paper, we compared two quantification methods: the stable isotope dilution assay (SIDA) and the diastereomeric dilution assay (DIDA). For this purpose, non-natural analogues of OTA were synthesized: the labeled OTA (OTA-d₄) as a diastereomeric mixture for the SIDA and one non-natural OTA’s diastereomer (OTA-dia) for the DIDA. To quantify OTA in red grapes, musts or wines, the sample preparation was optimized using immunoaffinity column extraction and the analysis was performed by LC–MS/MS in Multiple Reaction Monitoring mode. A validation procedure in agreement with the International Organization of Vine and Wine recommendations was conducted. It appeared that SIDA quantification exhibited excellent sensitivity (LOD < 1 ng L⁻¹), accuracy (recovery = 98%), repeatability (RSD < 3%) and intermediate reproducibility (RSD < 4%) compared to quantification by DIDA. Indeed, DIDA method did not provide satisfactory results demonstrating that immunoaffinity extraction is exclusively selective for the natural OTA and not for its diastereomer, which therefore cannot be considered as a good internal standard for this particular method.     

862 — The sequence and energetics of cell membrane transductive coupling to intracellular enzyme systems

We have shown that weak oscillating electromagnetic fields in the pericellular environment modulate key steps in coupling of signals from humoral stimuli at cell surface receptors to intracellular systems. This paper summarizes evidence that enzymatic activity within the cell provides sensitive molecular markers about both the sequence and the energetics of transmembrane coupling mechanisms. As research tools, these imposed fields appear to offer unique opportunities for understanding highly non-linear, non-equilibrium aspects of these coupling mechanisms, including the basis for amplification of weak pericellular stimuli to achieve an energetic threshold in signaling to intracellular enzyme systems.A three-stage model of membrane transductive coupling is proposed: a first stage in which weak pericellular electrochemical oscillations and binding of humoral stimulating molecules at receptor sites initiates a highly cooperative modification of calcium binding, a second stage involving transmission of signals initiated at receptor sites to the cell interior; and a third stage dealing with intracellular response to the transmembrane signal.Low frequency pulsed magnetic fields modulate stimulation of adenylate cyclase by parathyroid hormone (PTH) in bone cells. From collateral studies of field effects on PTH-binding to its receptor and from studies of fluoride activation of adenylate cyclase, there is evidence that an important field action is on membrane coupling proteins between receptors for PTH and adenylate cyclase.In addition to an action on adenylate cyclase, weak pericellular fields modulate activity of messenger enzymes, the protein kinases, and of an enzyme essential for cell growth, omithine decarboxylase. In human lymphocytes, cAMP-independent protein kinases are transiently inhibited by exposure to weak (athermal) microwave fields sinusoidally modulated at 16 Hz. In liver and ovary cells exposed to the same fields, and in bone cells exposed to low frequency pulsed magnetic fields, omithine decarboxylase activity is increased.Experimental data and models interrelating the pericellular electrochemical environment, cancer-promoting phorbol esters and activities of protein kinases and ornithine decarboxylase are discussed.     

A biacylhydrazone-based chemosensor for fluorescence ‘turn-on’ detection of Al3+ with high selectivity and sensitivity

A simple Al³⁺ fluorescent chemosensor (1) based on diacylhydrazone has been designed and synthesized by the condensation reaction of 2-hydroxy naphthaldehyde and metaphthalic hydrazide. The chemosensor 1 displays a specific and sensitive response to Al³⁺ over other cations in DMSO solution. Upon the addition of DMSO solution of Al³⁺, the sensor 1 shows an immediate fluorescence ‘turn-on’ response and emitting strong blue emission with visible color change from colorless to green. The fluorescence quantum yield enhanced from 7.24% to 48.68%. Meanwhile, the fluorescence and UV absorption spectra detection limits of the chemosensor 1 for Al³⁺ were 2.0 × 10^?7 M and 5.6 × 10^?7 M respectively, indicating the high sensitivity of 1 to Al³⁺. Furthermore, test strips based on 1 were fabricated, which could be used as a convenient test kit for the detection of Al³⁺ and an efficient Al³⁺ controlled fluorescent security display materials.     

Recombinant drugs-on-a-chip: The usage of capillary electrophoresis and trends in miniaturized systems – A review

We present here a critical review covering conventional analytical tools of recombinant drug analysis and discuss their evolution towards miniaturized systems foreseeing a possible unique recombinant drug-on-a-chip device. Recombinant protein drugs and/or pro-drug analysis require sensitive and reproducible analytical techniques for quality control to ensure safety and efficacy of drugs according to regulatory agencies. The versatility of miniaturized systems combined with their low-cost could become a major trend in recombinant drugs and bioprocess analysis. Miniaturized systems are capable of performing conventional analytical and proteomic tasks, allowing for interfaces with other powerful techniques, such as mass spectrometry. Microdevices can be applied during the different stages of recombinant drug processing, such as gene isolation, DNA amplification, cell culture, protein expression, protein separation, and analysis. In addition, organs-on-chips have appeared as a viable alternative to testing biodrug pharmacokinetics and pharmacodynamics, demonstrating the capabilities of the miniaturized systems. The integration of individual established microfluidic operations and analytical tools in a single device is a challenge to be overcome to achieve a unique recombinant drug-on-a-chip device.     

Stability improvement under high efficiency—next stage development of perovskite solar cells

With efficiency of perovskite solar cells(PSCs) overpassing 23%, to realize their commercialization, the biggest challenge now is to boost the stability to the same level as conventional solar cells. Thus, tremendous effort has been directed over the past few years toward improving the stability of these cells. Various methods were used to improve the stability of bulk perovskites,including compositional engineering, interface adjustment, dimensional manipulation, crystal engineering, and grain boundary decoration. Diverse device configurations, carrier transporting layers, and counter electrodes are investigated. To compare the stability of PSCs and clarify the degradation mechanism, diverse characterization methods were developed. Overall stability of PSCs has become one central topic for the development of PSCs. In this review, we summarize the state-of-the-art progress on the improvement of device stability and discuss the directions for future research, hoping it provides an overview of the current status of the research on the stability of PSCs and guidelines for future research.     

Synthesis of chloroboron(III) 3,4,12,13,21,22- hexabromosubnaphthalocyanine under high dilution conditions and comparative studies of effects of halogenation on physicochemical properties of subnaphthalocyanines

Chloroboron(III) hexabromosubnaphthalocyanine was prepared by cyclotrimerization of 6,7-dibromo-2,3-naphthalenedicarbonitrile in the presence of BCl₃ under high dilution conditions, that is 7.4?mM of dicarbonitrile in o-dichlorobenzene-xylene (1:1). It was converted to fluoroboron(III) hexabromosubnaphthalocyanine by the reaction with AgBF₄. Fluorescence quantum yields of chloroboron(III) hexafluoro-, hexachloro-, hexabromo-, and hexaiodosubnaphthalocyanine were 0.22, 0.20, 0.11, 0.05, respectively, indicating that heavy atom effects of Br and I effectively deactivated the singlet excited states. Thermal decomposition temperature (5% weight loss in the TG curve) of fluoroboron(III) hexabromosubnaphthalocyanine was the highest (359?°C) and that of chloroboron(III) hexafluorosubnaphthalocyanine was the lowest (221?°C) among hexahalosubnaphthalocyanines. The hexabromosubnaphthalocyanine served as a substrate of Sonogashira coupling, and proved to be a useful intermediate for further functionalization of subnaphthalocyanines.     

Effects of binders and graphite on the sensitivity of ε-HNIW

In order to optimize formulations of PBX based on Hexanitrohexaazaisowurtzitane (HNIW) and meet the application in mixed explosive, the mold powder of HNIW coated by varied binders was obtained by aqueous suspension technology. Several particle sizes of graphite were added as additive with a 0.5 % mass ratio. The experiment results showed that fluorine resin (FPM) was better than polyurethane and cis-butadiene rubber when the mass percentage of binders was fixed at 4 %. The characteristic height of HNIW/FPM (96/4) mold powder was at 28 cm (2.5 kg hammer), while that of the neat HNIW was at 15 cm merely, and the friction explosion probability fell from 100 to 70 %. The addition of flake graphite with proper grain size would reduce the mechanical sensitivity of HNIW and improved the fluxion property of HNIW-based mold powders. The thermal stability characteristic of HNIW FPM (96/4) and HNIW/FPM/G (96/4/0.5) were studied by thermogravimetric analysis (TG) at 10 °C min^?1, the peak decomposition temperatures were at 251 and 250 °C, which were closed to that of neat HNIW(249 °C) and also identified superior thermal stability of compound.     

Determination of thyroxine and 3,5,3′-triiodothyronine by sub- and super-equivalence isotope dilution analysis

Trace amounts of thyroxine in model samples (160.0 ng.ml^–1 and 20.0 ng.ml^–1), and thyroxine and 3,5,3-triiodothyronine in blood plasma were determined by sub- superequivalence isotope dilution analysis and radio-immunoassay technique. Hormones were labelled by¹²⁵I. The separation of antibody-bound hormone from free hormone was performed by ultracentrifugation. The results show higher accuracy of the sub- super-equivalence isotope dilution method over that of radioimunoassay.     

The cation exchange resin-promoted coupling of alkynes with aldehydes: one-pot synthesis of α,β-unsaturated ketones

Alkynes undergo smooth coupling with aldehydes in the presence of Amberlyst-15^® at room temperature to produce the corresponding α,β-unsaturated ketones in high yields with E-geometry. The use of an inexpensive, readily available, and recyclable cation exchange resin makes this method quite simple and convenient.     

The Solvation of Carbenes: π and O-Ylidic Complexes of p-Nitrophenylchlorocarbene

p-Nitrophenylchlorocarbene (PNPCC) was studied by laser flash photolysis with UV-vis detection in solution at ambient temperature. The π → p (316 nm) and σ → p (628 nm) absorptions of PNPCC were replaced in π- or O-donor solvents by absorptions due to π- or O-ylidic complexes or O-ylides. Donors included anisole, 1,3-dimethoxybenzene, 1,3,4,5-tetramethoxybenzene, diethyl ether, 18-crown-6, and dibenzo-18-crown-6. Suggestive evidence was also obtained for weak π-complexation of PNPCC by benzene. Computational studies aided in understanding the carbene complex and O-ylide absorption spectra, and they provided structures and energetics for these species.