Intrinsic Apyrase-Like Activity of Cerium-Based Metal–Organic Frameworks (MOFs): Dephosphorylation of Adenosine Tri- and Diphosphate

Apyrase is an important family of extracellular enzymes that catalyse the hydrolysis of high-energy phosphate bonds (HEPBs) in ATP and ADP, thereby modulating many physiological processes and driving life activities. Herein, we report an unexpected discovery that cerium-based metal–organic frameworks (Ce-MOFs) of UiO-66(Ce) have intrinsic apyrase-like activity for ATP/ADP-related physiological processes. The abundant Ce^III/Ce^IV couple sites of Ce-MOFs endow them with the ability to selectively catalyse the hydrolysis of HEPBs of ATP and ADP under physiological conditions. Compared to natural enzymes, they could resist extreme pH and temperature, and present a broad range of working conditions. Based on this finding, a significant inhibitory effect on ADP-induced platelet aggregation was observed upon exposing the platelet-rich plasma (PRP) to the biomimetic UiO-66(Ce) films, prefiguring their wide application potentials in medicine and biotechnology.     

New Supercage Metal–Organic Framework Based on Allopurinol Ligands Showing Acetylene Storage and Separation

To develop efficient adsorbent materials for storage and separation of C₂H₂, an unprecedented supercage MOF, [Me₂NH₂]⋅[Zn₃(ALP)(TDC)_2.5]⋅3.5DMF⋅2 H₂O ( 1 ) was constructed through medicinal molecule allopurinol (ALP) and S-containing 2,5-thiophenedicarboxylic acid (H₂TDC). 1 contains a novel linear trinuclear cluster that is composed by ALP and carboxylates and forms a final uncommon 5-connected yfy topological framework. The framework possesses three types of interlinked cages decorated by rich functional sites, and reveals not only high adsorption capacity for C₂H₂ but also excellent selective separation for C₂H₂/CO₂ and C₂H₂/CH₄ at 298 K. Dynamic breakthrough experiments on C₂H₂/CO₂ (1:1) mixture and C₂H₂/CH₄ (1:1) mixture also demonstrated the potential of the material to separate C₂H₂ from CO₂ or CH₄ mixtures. Molecular simulations were also studied to identify the different CO₂- and C₂H₂- binding sites in 1 , such as carboxylate groups, S atoms and carbonyl groups.     

Synthesis,crystal structure and conformational analysis of an unexpected [1,5]dithiocine product of aminopyridine and thiovanillin

The condensation reaction of 2‐mercapto‐3‐methoxybenzaldehyde with 3‐aminopyridine afforded an unexpected N‐alkylated [1,5]dithiocine instead of the N‐salicylideneaniline. The proposed mechanism for this condensation involves a strong intramolecular hydrogen bond between the thiol and the amine groups, leading to a second condensation. The corresponding product, i.e. 4,10‐dimethoxy‐13‐(pyridin‐3‐yl)‐6H,12H‐6,12‐epiminodibenzo[b,f][1,5]dithiocine methanol 0.463‐solvate, C₂₁H₁₈N₂O₂S₂·0.463CH₃OH, was characterized by single‐crystal X‐ray diffraction analysis. The supramolecular structure shows π–π stacking and S…S interactions in the crystal packing. Within the asymmetric unit, two geometries of the N atom are observed. Although a planar geometry should be expected, a pyramidal one is observed due to the crystal packing. The presence of the two geometries was further supported by density functional theory (DFT) calculations that show an electronic energy difference of less than 2 kJ mol^?1 between the two conformers.     

Improving waterproof/breathable performance of electrospun poly(vinylidene fluoride) fibrous membranes by thermo‐pressing

Facing the ever‐increasing demand for waterproof/breathable materials, a rapid and efficient fabrication method of these functional materials with excellent performance as well as robust mechanical properties remains challenging. Herein, a simple and scalable strategy referred to as thermo‐pressing is introduced to improve the waterproof/breathable performance and mechanical properties of electrospun PVDF fibrous membranes. The synergistic effect of temperature and pressure acted on the electrospun PVDF membranes on the fiber morphology and crystal structure was investigated, which can be able to effectively enhance waterproof performance and mechanical properties, endowing the as‐prepared membranes with a modest breathability. The membranes thermo‐pressed at 150 °C with a pressure of 8.27 MPa exhibit robust tensile strength of 40.65 MPa, which is superior to those of the previous reports (below 32.8 MPa). Notably, the optimized membranes enable to show a high hydrostatic pressure of 102 kPa, good WVTR of 10.87 kg m⁻² d⁻¹ and excellent abrasion resistance, which implies that the thermo‐pressing is an efficient and facile way to steer the fiber morphology and crystal structure of electrospun membranes to improve their application performance. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018 , 56, 36–45     

The formation of an oscillating system during the sputtering of sapphire single crystal with pulsed glow discharge

Sapphire (α-Al₂O₃, transparent corundum) single crystals were analyzed with pulsed direct current glow discharge mass spectrometry. Combined hollow cathode was used as a discharge cell. To obtain stable sputtering of dielectric material, a formation of initial surface conductivity via preliminary vacuum deposition of thin metallic layer was proposed. Al and Ta film of different thickness (30–200 nm) were considered for this purpose. The approach was found to provide the effective sputtering of dielectrics. The formation of an oscillating system was shown during the sputtering of sapphire samples in a tantalum combined hollow cathode cell. For oriented sapphire single crystals, periodic oscillations of ²⁷Al⁺ intensity were acquired. This phenomenon was observed only for dielectric single crystals and not for other dielectric samples, e.g. alumina ceramic or fused quartz. The linear dependence of oscillation period on the duration of discharge pulse was found. The origin of these oscillations seems to be attributed to periodic fluctuations of surface conductivity. Oscillation periods calculated for two different orientations of sapphire single crystals (001 and 012) were found to be proportional to the main period of sapphire lattice. Therefore, an assumption that the crystal internal structure of the sample might be the cause of the oscillations is discussed.     

Theory of radiation from relativistic positrons moving in the 〈110〉 axial channels of f.c.c. (diamond) crystal

The emission of radiation from relativistic positrons moving in the 〈110〉 axial channels of an f.c.c. (diamond) crystal has been studied. An expression for the radiation intensity has been obtained for the general case of positron motion. This expression has been simplified for the particular case of well-collimated incident beam. Enhancement of the radiation over (ordinary) bremsstrahlung has been discussed.     

可调谐激光晶体S因子和声子能量的估算

本文采用了一种特别的多模电-声子耦合模型,利用室温光谱数据估算可调谐激光晶体的黄昆-里斯(Huang-Rhys)S因子,并与单模耦合模型的结果作了比较.最后,还讨论了S因子与晶场强度及基质晶体价键特性之间的关系.     

单晶YSZ的Xe+离子辐照效应研究

200keV Xe+离子辐照使单晶YSZ由无色透明变成紫色透明,结果表明,能量为200keV,注量为1×1017cm-22的Xe+离子辐照YSZ单晶产生的损伤高达350dpa,在损伤区产生高密度的缺陷,但仍然没有发生非晶化转变。吸收光谱测试结果表明,产生吸收带的注量阈值大约为1016cm-2。注量为1×1016cm-2和1×1017cm-2的样品,吸收带峰值分别位于522nm和497nm。光吸收带可能与Zr阳离子最近邻的氧空位捕获电子形成的F型色心和Y阳离子近邻的氧离子捕获空穴形成的V型色心有关。     

Rotational viscosity of a liquid crystal mixture: a fully atomistic molecular dynamics study

Fully atomistic molecular dynamics (MD) simulations at 293, 303 and 313~K have been performed for the four-component liquid crystal mixture, E7, using the software package Material Studio. Order parameters and orientational time correlation functions (TCFs) were calculated from MD trajectories. The rotational viscosity coefficients (RVCs) of the mixture were calculated using the Nemtsov--Zakharov and Fialkowski methods based on statistical-mechanical approaches. Temperature dependences of RVC and density were discussed in detail. Reasonable agreement between the simulated and experimental values was found.     

Crystal structure of simple metals at high pressures

The effects of pressure on the crystal structure of simple (or sp-) elements are analysed in terms of changes in coordination number, packing density, and interatomic distances, and general rules are established. In the polyvalent elements from groups 14–17, the covalently bonded structures tend to transform to metallic phases with a gradual increase in coordination number and packing density, a behaviour normally expected under pressure. Group 1 and 2 metallic elements, however, show a reverse trend towards structures with low packing density due to intricate changes in their electronic structure. Complex crystal structures such as host–guest and incommensurately modulated structures found in these elements are given special attention in this review in an attempt to determine their role in the observed phase-transition sequences.