Determination of some reactive oxygen species scavengers based on the peroxidase-oxidase oscillator

This paper reports a new method for detection of ROS scavengers including superoxide dismutase, ascorbic acid and glutathione based on a 'probe' of peroxidase-oxidase biochemical oscillator. The oscillation period and amplitude change with different concentrations of scavengers. The linear ranges of superoxide dismutase, ascorbic acid and glutathione are respectively 1.56 x 10(-4)-1.56 x 10(-3) mg mL(-1), 1.75 x 10(-7)-1.75 x 10(-5) mol L(-1) and 9.38 x 10(-7)-7.5 x 10(-5) mol L(-1). The selectivity, linearity and precision for superoxide dismutase, ascorbic acid, and glutathione are presented and discussed. The results compared well with other standard methods for determination of superoxide dismutase, ascorbic acid and glutathione. Some possible steps in the overall reaction mechanisms are discussed.     

Voltammetric study of the interaction of lomefloxacin (LMF)–Mg(II) complex with DNA and its analytical application

The voltammetric behavior of the LMF-Mg(II) complex with DNA at a mercury electrode is reported for the first time. In NH₃–NH₄Cl buffer (pH=9.10), the adsorption phenomena of the LMF–Mg(II) complex were observed by linear sweep voltammetry. The mechanism of the electrode reaction was found to be a reduction of LMF in the complex, and the composition of the LMF–Mg(II) complex is 2:1. In the presence of calf thymus DNA (ctDNA), the peak current of LMF–Mg(II) complex decreased considerably, and a new well-defined adsorptive reduction peak appeared at −1.63 V (vs. SCE). The electrochemical kinetic parameters and the binding number of LMF–Mg(II) with ctDNA were also obtained. Moreover, the new peak currents of LMF–Mg(II)–DNA system increased linearly correlated to the concentration of DNA in the 4.00×10⁻⁷–2.60×10⁻⁶ g ml⁻¹ range when the concentrations of LMF–Mg(II) complex was fixed at 5.00×10⁻⁶ mol l⁻¹, with the detection limits of 2.33×10⁻⁷ g ml⁻¹. An electrostatic interaction was suggested by electrochemical method.     

Solubility of Icariin in a Binary Solvent System of Ethanol and Water

The solubility of icariin in the binary solvent system of ethanol and water was measured by UV–Vis spectrophotometry from 288.2 to 328.2 K. The solubility of icariin in the system increased with increasing temperature. A synergistic effect appeared at x ₂ = 0.4 (equivalent to 68.34 % ethanol, v/v) binary mixture. Solubility data were correlated with the modified Apelblat equation. The enthalpy and entropy of solution were evaluated using van’t Hoff plots.     

Copper-free Sonogashira cross-coupling for functionalization of alkyne-encoded proteins in aqueous medium and in bacterial cells

Bioorthogonal reactions suitable for functionalization of genetically or metabolically encoded alkynes, for example, copper-catalyzed azide-alkyne cycloaddition reaction ("click chemistry"), have provided chemical tools to study biomolecular dynamics and function in living systems. Despite its prominence in organic synthesis, copper-free Sonogashira cross-coupling reaction suitable for biological applications has not been reported. In this work, we report the discovery of a robust aminopyrimidine-palladium(II) complex for copper-free Sonogashira cross-coupling that enables selective functionalization of a homopropargylglycine (HPG)-encoded ubiquitin protein in aqueous medium. A wide range of aromatic groups including fluorophores and fluorinated aromatic compounds can be readily introduced into the HPG-containing ubiquitin under mild conditions with good to excellent yields. The suitability of this reaction for functionalization of HPG-encoded ubiquitin in Escherichia coli was also demonstrated. The high efficiency of this new catalytic system should greatly enhance the utility of Sonogashira cross-coupling in bioorthogonal chemistry.     

ATR-FTIR study of Bacillus sp. and Escherichia coli settlements on the bare and Al2O3 coated ZnSe internal reflection element

FTIR-ATR has been used for understanding the interaction between bacteria and surfaces in the adsorption progress.     

In situ real-time study buckling behavior of boron nitride nanotubes with axial compression by TEM

The real time analysis structure evolution of BNNT with compression showed that the formation of V-shape in the post-buckling before BNNT fracture was reversible.     

A Metal–Organic Supramolecular Box as a Universal Reservoir of UV,WL, and NIR Light for Long‐Persistent Luminescence

Long persistent luminescence (LPL) materials have a unique photophysical mechanism to store light radiation energy for subsequent release. However, in comparison to the common UV source, white‐light (WL) and near‐infrared (NIR) excited LPL is scarce. Herein we report a metal–organic supramolecular box based on a D–π–A‐type ligand. Owing to the integrated one‐photon absorption (OPA) and two‐photon absorption (TPA) attributes of the ligand, the heavy‐atom effect of the metal center, as well as π‐stacking and J‐aggregation states in the supramolecular assembly, LPL can be triggered by all wavebands from the UV to the NIR region. This novel designed supramolecular kit to afford LPL by both OPA and TPA pathways provides potential applications in anti‐counterfeiting, camouflaging, decorating, and displaying, among others.     

Semiconductor Nanocrystal Engineering by Applying Thiol‐ and Solvent‐Coordinated Cation Exchange Kinetics

Thiol‐ and solvent‐coordinated cation exchange kinetics have been applied to engineer the composition and crystallinity of novel nanocrystals. The detailed thermodynamics and kinetics of the reactions were explored by NMR spectroscopy, time‐dependent photoluminescence (PL) characterizations and theoretical simulations. The fine structure of the colloidal semiconductor nanocrystals (CSNCs) was investigated by X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS). In this way, high‐quality p‐type Ag‐doped ZnS quantum dots (QDs) and Au@ZnS hetero‐nanocrystals with a cubic phase ZnS shell were synthesized successfully.The unprecedented dominant Ag⁺‐dopant‐induced fluorescence and p‐type conductivity in the zinc‐blende ZnS are reported.     

The influence of temperature on the phase behavior of ionic liquid aqueous two-phase systems

In this article, the equilibrium behavior of solutions of 1-ethyl-3-methylimidazolium dimethyl phosphate ([Emim]DMP) and ethyl acetate or acetone in aqueous two-phase system (ATPS) was discussed to understand the liquid–liquid equilibrium (LLE) behavior of these organic solvents. Thus, we determined phase diagrams and LLE data at 303.15, 308.15, 313.15, and 323.15 K for the investigated biphasic systems. Four empirical equations were used to study the tie lines. The results showed that for the [Emim]DMP?+?acetone?+?water biphasic systems within the investigated temperature range, temperature influences the phase behavior, but for the [Emim]DMP?+?ethyl acetate?+?water biphasic systems within the investigated temperature range, there are no notable changes on the phase behavior with rising temperature. The results may have important applications for the separation of antibiotics and for the recovery of ionic liquids (ILs).