Study on the preparation and mechanical properties of purple ceramics.

This paper aims at preparing a smart wearable purple ceramic that meet the color requirements of purple smart wear in the market after using zirconate neodymium as a chromogenic agent. However, the mechanical performance of zirconate neodymium purple ceramic is not satisfactory, especially it has an extremely low fracture toughness. To solve this, a 3 mol% yttria-stabilized zirconia (3YSZ) is added to zirconate neodymium in the preparation of multiphase ceramics to improve its mechanical properties. In this experiment, a series of ceramic samples with addition of increasing amount of 3YSZ 0, 20, 40, 50, 60, 70 and 80% were prepared in the 1400-1500 °C sintering temperature range. It was found that at the same temperature, the mechanical properties of the ceramic samples gradually improved with the increase in the 3YSZ content. Moreover, with the same content, the mechanical properties of the ceramic samples gradually improved with the decrease in temperature. The results show that when 3YSZ has a mass fraction of 80% and is sintered at 1400 °C, the fracture toughness of the prepared ceramic samples reaches 8.15 MPa‧m1/2, which is nearly two times higher than that of the monolithic neodymium zirconate 2.57 MPa‧m1/2. The Vickers hardness of the prepared ceramic samples reached 12.93 GPa, which is nearly 88% higher than the undoped neodymium zirconate. This indicates that the samples can be applied in smart wearables, such as mobile phone backplane, with a certain practical significance for engineering toughening of zirconate ceramics.

Improved Durability of High-Performance Intermediate-Temperature Solid Oxide Fuel Cells with a Ba-Doped La0.6Sr0.4Co0.2Fe0.8O3-δ Cathode.

As a device for direct conversion of chemical energy into electrical energy, the solid oxide fuel cell (SOFC) contributes positively to the sustainable development strategy. However, the commercialization of fuel cells is still impeded by severe cathode degradation caused by its limited stability at operating temperatures and being prone to Cr-poisoning from Cr-containing alloy interconnectors commonly used in these cells. This paper reports the development of a high-durability Ba-doped LSCF(La0.6Sr0.4Co0.2Fe0.8O3-δ) cathode material under realistic fuel cell operating conditions in the presence of the Cr alloy. In particular, when tested in a symmetrical cell constructed of Ba-doped LSCF, the polarization resistance of the cell remains very low at 0.06 Ω cm2 after being tested at 800 °C for 120 h exposed to Cr in 3% humidified air. In contrast, for the undoped LSCF under the same testing conditions, the polarization resistance of the cell increases ∼10 times from 0.22 Ω cm2 of the pristine cell to 2.18 Ω cm2 after Cr-exposure testing. Furthermore, when tested in an anode-supported complete cell as a cathode under typical SOFC operation conditions at 750 °C, the cell with the Ba-doped LSCF cathode displays significantly low degradation rates of 0.00056% h-1 (without Cr) and 0.00310% h-1 (with Cr); both are much lower than that of the cell using the undoped LSCF cathode (0.00124% h-1 without Cr and 0.01082% h-1 with Cr). This enhanced durability and Cr-tolerance exhibited by the Ba-doped LSCF cathode stem from its higher crystal structure stability and improved chemical resistance compared to undoped LSCF.

Rational Design of P450 aMOx for Improving Anti-Markovnikov Selectivity Based on the "Butterfly" Model.

Aromatic aldehydes are important industrial raw materials mainly synthesized by anti-Markovnikov (AM) oxidation of corresponding aromatic olefins. The AM product selectivity remains a big challenge. P450 aMOx is the first reported enzyme that could catalyze AM oxidation of aromatic olefins. Here, we reported a rational design strategy based on the "butterfly" model of the active site of P450 aMOx. Constrained molecular dynamic simulations and a binding energy analysis of key residuals combined with an experimental alanine scan were applied. As a result, the mutant A275G showed high AM selectivity of >99%. The results also proved that the "butterfly" model is an effective design strategy for enzymes.

The Grain Growth Control of ZnO-V2O5 Based Varistors by PrMnO3 Addition.

In this study, the grain growth behaviour of ZnO-V2O5-based ceramics with 0.25-0.75 mol% additions of PrMnO3 was systematically investigated during sintering from 850 °C to 925 °C. with the aim to control the ZnO grain size for their application as varistors. It was found that with the increased addition of PrMnO3, in addition to the decrease in the average grain size, the grain size distribution also narrowed and eventually changed from a bimodal to unimodal distribution after a 0.75 mol% PrMnO3 addition. The grain growth control was achieved by a pinning effect of the secondary ZnCr2O4 and PrVO4 phases at the ZnO grain boundaries. The apparent activation energy of the ZnO grain growth in these ceramics was found to increase with increased additions of PrVO4, hence the observed reduction in the ZnO grain sizes.

Enhancing CO2 Catalytic Adsorption on an Fe Nanoparticle-Decorated LaSrFeO4 + δ Cathode for CO2 Electrolysis.

The development of cathode materials with high catalytic activity and low cost is a challenge for CO2 electrolysis based on solid oxide electrolysis cells. Herein, we report a low-cost and highly active metallic Fe nanoparticle-decorated Ruddlesden-Popper (La, Sr)FeO4+δ cathode catalyst (Fe-RPLSF), which shows a high oxygen vacancy concentration and robust CO2 reduction rate. At 850 °C, the current density of the electrolysis cell with the Fe-RPLSF cathode reaches -1920 mA cm-2 at a voltage of 1.5 V, and the Faraday efficiency is as high as 100%. The polarization resistance at low frequency (0.1-10 Hz), which is the rate-limit step for CO2 electrolysis, significantly decreases with the exsolved Fe nanoparticles because of improved CO2 dissociative adsorption. Moreover, our electrolysis cell demonstrates acceptable short-term stability for direct CO2 electrolysis.

Alanine scanning combined with interaction entropy studying the differences of binding mechanism on HIV-1 and HIV-2 proteases with inhibitor.

Quantitative characterization of binding affinity in protein-ligand and residue-ligand is critical for understanding binding mechanisms of protein-ligand and predicting hot-spot residues. In this paper, binding free energies between two HIV (HIV-1 and HIV-2) proteases and four inhibitors are calculated by molecular mechanics/generalized Born surface area (MM/GBSA) combined with the newly developed interaction entropy (IE) approach. The internal dielectric constant is set on the basis of different types of amino acids. The entropy change in protein-ligand binding is computed by IE method which is superior to the traditional normal mode (Nmode) method in the analysis of the ranking of binding free energy, statistical stability and enthalpy-entropy compensation. Importantly, IE method combined with alanine scanning is applied to calculate residue-specific binding free energy. And the calculated total binding free energy using the current method is in excellent with the experimental observed. Our research indicates that HIV-1 and HIV-2 proteases share the common hot-spot residues with ILE50/50' and ILE84/ILE84' which provide the major favorable contribution to the binding of protein and inhibitor in all systems. The predicted hot-spot residues are more in HIV-1 complex than HIV-2 complex and some hot-spot residues contributing to HIV-1 don't play a significant role in HIV-2. To some extent, this explains the reason of decrease in potency inhibitors against HIV-2 compared to HIV-1 protease. The study is expected to understand quantitatively the binding mechanism of HIV-inhibitor and provide important theoretical guidance for the design of equipotent HIV-1/HIV-2 protease inhibitors.Communicated by Ramaswamy H. Sarma.

Molecular Mechanism of Selective Binding of NMS-P118 to PARP-1 and PARP-2: A Computational Perspective.

The nuclear protein poly (ADP-ribose) polymerase-1 (PARP-1) inhibitors have been proven effective to potentiate both chemotherapeutic agents and radiotherapy. However, a major problem of most current PARP inhibitors is their lack of selectivity for PARP-1 and its closest isoform PARP-2. NMS-P118 is a highly selective PARP inhibitor that binds PARP-1 stronger than PARP-2 and has many advantages such as excellent pharmacokinetic profiles. In this study, molecular dynamics (MD) simulations of NMS-P118 in complex with PARP-1 and PARP-2 were performed to understand the molecular mechanism of its selectivity. Alanine scanning together with free energy calculation using MM/GBSA and interaction entropy reveal key residues that are responsible for the selectivity. Although the conformation of the binding pockets and NMS-P118 are very similar in PARP-1 and PARP-2, most of the hot-spot residues in PARP-1 have stronger binding free energy than the corresponding residues in PARP-2. Detailed analysis of the binding energy shows that the 4'4-difluorocyclohexyl ring on NMS-P118 form favorable hydrophobic interaction with Y889 in PARP-1. In addition, the H862 residue in PARP-1 has stronger binding free energy than H428 in PARP-2, which is due to shorter distance and stronger hydrogen bonds. Moreover, the negatively charged E763 residue in PARP-1 forms stronger electrostatic interaction energy with the positively charged NMS-P118 than the Q332 residue in PARP-2. These results rationalize the selectivity of NMS-P118 and may be useful for designing novel selective PARP inhibitors.

Systematic Design of Trypsin Cleavage Site Mutated Exendin4-Cysteine 1, an Orally Bioavailable Glucagon-Like Peptide-1 Receptor Agonist.

Exendin-4 is a strong therapeutic candidate for the treatment of metabolic syndrome. Related receptor agonist drugs have been on the market since 2005. However, technical limitations and the pain caused by subcutaneous injection have severely limited patient compliance. The goal of the study is to investigate a biologically active exendin-4 analog could be administered orally. Using intraperitoneal glucose tolerance tests, we discovered that exendin4-cysteine administered by oral gavage had a distinct hypoglycemic effect in C57BL/6J mice. Using Rosetta Design and Amber, we designed and screened a series of exendin4-cysteine analogs to identify those that retained biological activity while resisting trypsin digestion. Trypsin Cleavage Site Mutated Exendin4-cysteine 1 (TSME-1), an analog whose bioactivity was similar to exendin-4 and was almost completely resistant to trypsin, was screened out. In addition, TSME-1 significantly normalized the blood glucose levels and the availability of TSME-1 was significantly higher than that of exendin-4 and exendin4-cysteine. Collectively orally administered TSME-1, a trypsin-resistant exendin-4 analog obtained by the system, is a strong candidate for future treatments of type 2 diabetes.