Separation of lithium isotope by NTOE compound

In recent years chances of using rhenium-186 and rhenium-188 as radioactive isotopes in diagnostic and therapeutic applications are increased very much due to the characteristic radiochemical and chemical properties of these two radioisotopes. In particular, chemical similarities between⁹⁹Tc and^99mTc pair and¹⁸⁶Re and¹⁸⁸Re pair make it easier to correlate the two groups of compounds. Rhenium-188 is generated from the beta-decay of tungsten-188 which was produced by double neutron capture on enriched tungsten-186 oxide. It is of great interest to examine the impurities in the eluate by radiochemical neutron activation. For this purpose, the preconcentration of the impurities in samples were necessary, and it was achieved by adsorption on hydrated magnesium oxide.     

Fourier transform ion cyclotron resonance study of multiply charged aggregates of small singly charged peptides formed by electrospray ionization

Aggregates of singly protonated peptides formed with a nanoelectrospray ion source have been observed in the gas phase using Fourier transform ion cyclotron resonance (FT-ICR). Employment of “soft” ion sampling conditions in the source, which were developed previously to generate water clusters of biomolecules, provides significant yields of aggregates of singly protonated GGDPG ([2GGDPG + 2H]²⁺), GGEPG ([2GGEPG + 2H]²⁺), and VEPIPY (2VEPIPY + 2H]²⁺). With peptide mixtures, heteroaggregates, e.g., [GGDPG + GGEPG + 2H]²⁺ have also been observed along with the homoaggregates. These weakly bound noncovalent complexes undergo facile exothermic dissociation into the corresponding singly protonated monomer species with normal operation of the electrospray ion source. For example, the aggregates were not observed in FT-ICR experiments utilizing a conventional electrospray ionization (ESI) or fast atom bombardment source or with a quadrupolar ion trap mass spectrometer equipped with a conventional ESI source. The formation and metastability of these aggregates are dependent on highly specific intermolecular hydrogen bonding between the monomers. The amino acid sequence (DPG) of GGDPG mimics the well-known β reverse turn of proteins and semiempirical calculations show that it provides excellent hydrogen bonding sites for a protonated N-terminus amino group. Support for this conjecture is provided by the failure to observe aggregate formation of singly protonated peptides with several larger peptides, including hexaglycine and hexaalanine.     

Elemental‐Sulfur‐Mediated Facile Synthesis of a Covalent Triazine Framework for High‐Performance Lithium–Sulfur Batteries

A covalent triazine framework (CTF) with embedded polymeric sulfur and a high sulfur content of 62 wt % was synthesized under catalyst‐ and solvent‐free reaction conditions from 1,4‐dicyanobenzene and elemental sulfur. Our synthetic approach introduces a new way of preparing CTFs under environmentally benign conditions by the direct utilization of elemental sulfur. The homogeneous sulfur distribution is due to the in situ formation of the framework structure, and chemical sulfur impregnation within the micropores of CTF effectively suppresses the dissolution of polysulfides into the electrolyte. Furthermore, the triazine framework facilitates electron and ion transport, which leads to a high‐performance lithium–sulfur battery.     

Catalytic effects of [Ag(H2O)(H3PW11O39)]3− on a TiO2 anode for water oxidation

A [H₃Ag^I(H₂O)PW₁₁O₃₉]^3?-TiO₂/ITO electrode was fabricated by immobilizing a molecular polyoxometalate-based water oxidation catalyst, [H₃Ag^I(H₂O)PW₁₁O₃₉]^3? (AgPW₁₁), on a TiO₂ electrode. The resulting electrode was characterized by X-ray powder diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy. Linear sweep voltammetry, chronoamperometry, and electrochemical impedance measurements were performed in aqueous Na₂SO₄ solution (0.1 mol L^?1). We found that a higher applied voltage led to better catalytic performance by AgPW₁₁. The AgPW₁₁-TiO₂/ITO electrode gave currents respectively 10 and 2.5 times as high as those of the TiO₂/ITO and AgNO₃-TiO₂/ITO electrodes at an applied voltage of 1.5 V vs Ag/AgCl. This result was attributed to the lower charge transfer resistance at the electrode-electrolyte interface for the AgPW₁₁-TiO₂/ITO electrode. Under illumination, the photocurrent was not obviously enhanced although the total anode current increased. The AgPW₁₁-TiO₂/ITO electrode was relatively stable. Cyclic voltammetry of AgPW₁₁ was performed in phosphate buffer solution (0.1 mol L^?1). We found that oxidation of AgPW₁₁ was a quasi-reversible process related to one-electron and one-proton transfer. We deduced that disproportionation of the oxidized [H₂Ag^II(H₂O)PW₁₁O₃₉]^3? might have occurred and the resulting [H₃Ag^IIIOPW₁₁O₃₉]^3? oxidized water to O₂.     

Reductively Caged,Photoactivatable DNA‐PAINT for High‐Throughput Super‐resolution Microscopy

In DNA points accumulation in nanoscale topography (DNA‐PAINT), capable of single‐molecule localization microscopy with sub‐10‐nm resolution, the high background stemming from the unbound fluorescent probes in solution limits the imaging speed and throughput. Herein, we reductively cage the fluorescent DNA probes conjugated with a cyanine dye to hydrocyanine, acting as a photoactivatable dark state. The additional dark state from caging lowered the fluorescent background while enabling optically selective activation by total internal reflection (TIR) illumination at 405 nm. These benefits from “reductive caging” helped to increase the localization density or the imaging speed while preserving the image quality. With the aid of high‐density analysis, we could further increase the imaging speed of conventional DNA‐PAINT by two orders of magnitude, making DNA‐PAINT capable of high‐throughput super‐resolution imaging.     

Raman Spectroscopic Study on Alkyl Chain Conformation in 1‐Butyl‐3‐methylimidazolium Ionic Liquids and their Aqueous Mixtures

Ionic liquids of 1‐butyl‐3‐methylimidazolium ([BMIM]) cation with different anions (Cl^?, Br^?, I^?, and BF₄^?), and their aqueous mixtures were investigated by using Raman spectroscopy and dispersion‐included density functional theory (DFT). The characteristic Raman bands at 600 and 624 cm^?1 for two isomers of the butyl chain in the imidazolium cation showed significant changes in intensity for different anions as well as in aqueous solutions. The area ratio of these two bands followed the order I^?>Br^?>Cl^?>BF₄^? (in terms of the anion X in [BMIM]X), indicating that the butyl chain of [BMIM]I tends to adopt the trans conformation. The butyl chain was found to adopt the gauche conformation upon dilution, irrespective of the anion type. The Raman bands in the butyl C?H stretch region for [BMIM]X (X=Cl^?, Br^?, and I^?) blueshifted significantly with the increase in the water concentration, whereas that for [BMIM]BF₄ changed very little upon dilution. The blueshift in the C?H stretch region upon dilution also followed the order: [BMIM]I>[BMIM]Br>[BMIM]Cl>[BMIM]BF₄, the same order as the above trans conformation preference of the butyl chain in pure imidazolium ionic liquids, which suggested that the cation‐anion interaction plays a role in determining the conformation of the chain.     

Structural Analysis and Inhibitory Kinetics of Brain Type Creatine Kinase by Sodium Dodecyl Sulfate

The studies regarding the effect of sodium dodecyl sulfate (SDS) on enzyme activities and structures can provide a valuable insight into public health. We have predicted the 3D structure of the brain creatine kinase (CK-BB) with a high resolution and simulated the docking between CK-BB and SDS. The predicted structure had a root mean square deviation of 0.51 Å. The docking between CK-BB and SDS was successful with significant scores (?4.67 kcal/mol, AutoDock4 and ?48.32 kcal/mol, DOCK6). We have also investigated the inactivation by using SDS to study CK-BB’s folding behaviors. The two-phase rate constants as a first-order reaction were measured during inactivation. SDS strongly inhibited the CK-BB activity in a noncompetitive inhibition manner (K _i?=?1.22 mM). The tertiary structural change was induced by SDS binding with the exposure of hydrophobic surface. The methyl-β-cyclodextrin was used to strip SDS from the enzyme molecule to reactivate. The changes of thermodynamic parameters for the SDS ligand binding such as enthalpy, Gibbs free energy, and entropy were obtained as ?13?±?7.0 MJ/mol, 8.39 kJ/mol, and ?42.754 kJ/(K mol), respectively. Our study provides important structural information for CK-BB and its interaction with SDS with an insight on its folding and inhibition kinetics.     

丝氨酸在葡萄糖-水和蔗糖-水混合溶剂中的体积性质

利用精密数字密度计测定了丝氨酸与不同组成的葡萄糖-水、蔗糖-水混合溶剂构成的三元系溶液的密度，计算了丝氨酸的表观摩尔体积、极限偏摩尔体积和理论水化数.根据结构水合作用模型讨论了迁移偏摩尔体积的变化规律，并与乙二醇-水和丙三醇-水等多羟基体系作了比较.结果表明，丝氨酸分子在多羟基化合物-水体系中增体积效应的大小与多羟基化合物所含OH基数目的多少有关.     

Effect of the polarity of silver nanoparticles induced by ionic liquids on facilitated transport for the separation of propylene/propane mixtures

The effect of ionic liquids on the formation of a partial positive charge on the surface of silver nanoparticle and its subsequent effect on facilitated olefin transport were investigated. Three different ionic liquids of 1-butyl-3-methylimidazolium tetrafluoroborate (BMIM⁺BF₄⁻), 1-butyl-3-methylimidazolium triflate (BMIM⁺Tf⁻), and 1-butyl-3-methylimidazolium nitrate (BMIM⁺NO₃⁻) were employed to control the positive charge density of the surface of silver nanoparticles. The positive charge density of the silver nanoparticles, as characterized by the binding energy of the silver atom, was in the following order: BMIM⁺BF₄⁻/Ag ? BMIM⁺Tf⁻/Ag > BMIM⁺NO₃⁻/Ag. This order was consistent with the tendency of ionic liquids to form free ions. The best separation performance for the propylene/propane mixtures was a mixed gas selectivity of 17 and a permeance of 7 GPU through a composite membrane consisting of BMIM⁺BF₄⁻/Ag. A better separation performance for olefin/paraffin mixtures was observed with a higher positive charge density of the silver nanoparticles. It was therefore concluded that facilitated olefin transport was a direct consequence of the surface positive charge of the silver nanoparticles induced by ionic liquids.     

拍摄白光再现全息图的一种方法

本文给出了一种拍摄白光再现全息图装置 ,所拍的全息图在阳光或白炽灯照明下清晰地再现被拍的物体形象