Investigating the Influence of Amorphous/Crystalline Interfaces on the Stability of IrO2 for the Oxygen Evolution Reaction in Acidic Electrolyte

Posted on by
Investigating the Influence of Amorphous/Crystalline Interfaces on the Stability of IrO2 for the Oxygen Evolution Reaction in Acidic Electrolyte

Electrodeposited amorphous thin films of IrO2 are annealed at different temperatures to produce amorphous/crystalline interfaces. During oxygen evolution reaction at high current density their presence is found to influence both activity and stability/solubility of the electrode. Although increased performance is found, films are still prone to dissolution.


Abstract

A major challenge with water splitting technology is to develop highly active and stable electrocatalysts for the oxygen evolution reaction (OER). IrO2 – based electrocatalysts are one of the most active electrocatalysts for proton exchange membrane (PEM) electrolysers, due to their excellent activity for the OER in acidic conditions. However, IrO2 often suffers from dissolution during electrolysis due to phase transitions into more soluble forms. Herein, a range of electrodeposited IrO2 films annealed to different temperatures of up to 500°C are prepared to understand the influence that crystalline/amorphous interfaces have on performance during accelerated degradation tests in concentrated acidic solutions. This study showed that an IrO2 film annealed at 300 °C exhibited the highest catalytic activity with a low overpotential of 150 mV at 10 mA cm−2, the smallest Tafel slope of 51 mV dec−1, with a less progressive decay in activity over a period of 8 h of accelerated degradation testing. This contrasts with both fully amorphous or more crystalline IrO2 films that decayed much more rapidly within 1 h of testing indicating the role that amorphous/crystalline regions have on OER performance.

Reaction Engineering and Comparison of Electroenzymatic and Enzymatic ATP Regeneration Systems

Posted on by
Reaction Engineering and Comparison of Electroenzymatic and Enzymatic ATP Regeneration Systems

An electrochemically coupled ATP regeneration by pyruvate oxidase and acetate kinase for the phosphorylation of mevalonate was established and expanded by a polyphosphate kinase. The reaction was characterized and compared with other ATP regenerating systems in terms of the phosphate donor properties and biocatalytic metrics.


Abstract

Adenosine-5’-triphosphate (ATP) plays a crucial role in many biocatalytic reactions and its regeneration can influence the performance of a related enzymatic reaction significantly. Here, we established electrochemically coupled ATP regeneration by pyruvate oxidase and acetate kinase (ACK) for the phosphorylation of mevalonate catalyzed by mevalonate kinase. A yield of 84 % for the product mevalonate phosphate was reached and a total turnover number for ADP of 68. These metrics are promising for the development of an economic feasible bioprocess and surpass many other enzymatic ATP regeneration systems. A comparison was made to polyphosphate kinases (PPKs), ACK, pyruvate kinase, and creatine kinase in terms of the phosphate donor properties and biocatalytic metrics of exemplary reactions. Furthermore, our system was expanded by a PPK that enables the phosphorylation of AMP, which can broaden the spectrum of applications even further.

The size induced phase transition in the Rb0.95NbxMo2‐xO6.475‐0.5x (x = 1.31–1.663) solid solution with β‐pyrochlore structure

Posted on by

The size induced phase transition for non-cubic β-pyrochlore compounds Rb0.95NbxMo2-xO6.475-0.5x (x = 1.31–1.663) has been studied in detail. The Rb0.95NbxMo2-xO6.475-0.5x (x = 1.31–1.663) powders with different size particles have been prepared and investigated by X-ray powder diffraction analysis and scanning electron microscopy with X-ray microanalysis. The Rb0.95Nb1.5Mo0.5O5.73 and Rb0.95Nb1.375Mo0.625O5.79 powders consisted of ~ 20 µm crystals possess orthorhombic Pnma symmetry, whereas the same powders with particle size less 1 µm have cubic Fd-3m and characterized by decreasing Rb content - Rb0.7Nb1.5Mo0.5O5.58 and Rb0.9Nb1.625Mo0.375O5.62. The crystal structure of Rb0.7Nb1.5Mo0.5O5.58 cubic phase refinement has been performed using the Rietveld method; and crystallographic reasons of structure reconstruction have been discussed. The electronic structure and band gap of Rb0.95NbxMo2-xO6.475-0.5x (x = 1.31–1.663) compounds have been studied. Moreover the comparison of electronic structure for cubic and orthorhombic phases has been performed.

Inhibitory Effect of Salicin on Staphylococcus aureus Coagulase

Posted on by
Inhibitory Effect of Salicin on Staphylococcus aureus Coagulase

Coagulase (Coa) can bind and activate prothrombin, converting fibrinogen into fibrin, forming a fibrin network that protects S. aureus from host immune phagocytosis, and causes blood clotting. Salicin, as an inhibitor of S. aureus Coa, could also inhibit coagulation activity, interfere with the coagulation cascade, and protect mice from fatal pneumonia caused by S. aureus.


Abstract

The massive use of antibiotics has resulted in an alarming increase in antibiotic resistance in Staphylococcus aureus (S. aureus). This study aimed to identify the inhibitory effect of salicin on S. aureus. Coagulase (Coa) activity was assessed using in vitro Coa assays and Western blot, thermal shift assay (TSA), fluorescence quenching and molecular docking experiments were conducted to verify the interaction between salicin and Coa. An in vivo mouse pneumonia model demonstrated that salicin can reduce the virulence of S. aureus. In vitro Coa assays elucidated that salicin directly inhibited Coa activity. The Western blot and TSA results suggested that salicin did not block the expression of Coa but affected the thermal stability of the protein by binding to Coa. The fluorescence quenching, molecular docking and molecular dynamics assays have found that the most promising binding site between salicin and Coa was GLN-97. The pneumonia model of mice infected with S. aureus revealed that salicin could not only reduce the content of lung bacteria in mice but also prolong their survival. Salicin was identified as a novel anti-infective candidate compound with the potential to target Coa and inhibit its activity by binding to it, which would facilitate the development of roadmaps for future research.

Bidirectional Communication between Droplet Interface Bilayers Driven by Cell‐Free Quorum Sensing Gene Circuits

Posted on by
Bidirectional Communication between Droplet Interface Bilayers Driven by Cell-Free Quorum Sensing Gene Circuits

The Front Cover shows collections of communicating synthetic cells composed of water-in-oil droplets separated and stabilized by lipid bilayer interfaces and containing cell-free expression system with quorum sensing gene circuits. Cover design by David T. Gonzales. More information can be found in the Research Article by T.-Y. Dora Tang and co-worker.


Targeting EPHA2 with Kinase Inhibitors in Colorectal Cancer

Posted on by
Targeting EPHA2 with Kinase Inhibitors in Colorectal Cancer

Targeting the kinase EPHA2 in colorectal cancer (CRC): The kinase EPHA2 plays a role in the development and progression of CRC and seems to be involved in resistance mechanism towards a monoclonal antibody. This concept paper reviews the present results of targeting EPHA2 in CRC with small molecules and highlights the potential of this approach.


Abstract

The ephrin type-A 2 receptor tyrosine kinase (EPHA2) is involved in the development and progression of various cancer types, including colorectal cancer (CRC). There is also evidence that EPHA2 plays a key role in the development of resistance to the endothelial growth factor receptor (EGFR) monoclonal antibody Cetuximab used clinically in CRC. Despite the promising pharmacological potential of EPHA2, only a handful of specific inhibitors are currently available. In this concept paper, general strategies for EPHA2 inhibition with molecules of low molecular weight (small molecules) are described. Furthermore, available examples of inhibiting EPHA2 in CRC using small molecules are summarized, highlighting the potential of this approach.

Highly Efficient β‐Functionalized Oxidomolybdenum(V) Corroles for Catalytic Oxidative Bromination of Phenols at Room Temperature

Posted on by
Highly Efficient β-Functionalized Oxidomolybdenum(V) Corroles for Catalytic Oxidative Bromination of Phenols at Room Temperature

3-Formyl- and 3-dicyanovinyl-functionalized oxido-molybdenum corroles have been synthesized and utilized as an efficient catalyst with high TOF values (59801–71174 h−1) for oxidative bromination for a wide variety of phenol derivatives at room temperature in water in the presence of KBr/H2O2/HClO4 as brominating agent.


Abstract

Two new β-functionalized oxidomolybdenum(V) corroles, oxido[3-formyl-5,10,15-triphenylcorrolato]molybdenum(V) (Mo-1) and oxido[3-dicyanovinyl-5,10,15-triphenylcorrolato]molybdenum(V) (Mo-2) were synthesized and characterized by various spectroscopic techniques and electrochemical studies. Mo-2 manifests splitted B bands due to x and y polarizations and highly red shifted longest B and Q bands due to the electron-deficient nature of the dicyanovinyl group. EPR data showed that these complexes exhibit an axial compression with d xy 1 configuration. DFT studies revealed that HOMO and LUMO orbitals are stabilized in Mo-2 relative to Mo-1. Mo-1 exhibits two successive reversible reductions and two oxidation potentials in cyclic voltammetry. Surprisingly, Mo-2 exhibits three successive reversible reductions and two oxidations; the one extra reduction could possibly be due to the reduction of the dicyanovinyl moiety. The catalytic activities of Mo-1 and Mo-2 for the oxidative bromination of various phenols using H2O2-KBr-HClO4 mixture in water have been explored and exhibited excellent activity at a very low catalyst loading of 0.0030 and 0.0028 mol%, respectively. Both synthesized β-functionalized Mo(V) corroles manifest much higher conversion and TOF (59801–71174 h−1) for oxidative bromination of phenols relative to earlier reported meso-functionalized Mo(V) corroles (20781–61646 h−1). Hence, Mo-1 and Mo-2 mimic vanadium bromoperoxidase (VBPO) and act as functional models for these catalytic applications. These catalysts were reused upto 3 cycles and showed conversion rate upto 82 % indicating their excellent thermal and chemical stabilities.

Peptide and Peptidomimetic Assemblies in Dynamic Combinatorial Chemistry

Posted on by
Peptide and Peptidomimetic Assemblies in Dynamic Combinatorial Chemistry

The Cover Feature illustrates three strategies for the generation of dynamic combinatorial libraries (DCLs) of peptide or peptidomimetic-based assemblies. Exploring their self-adaptative potential can lead to the discovery of smart nanomaterials, drug nanocarriers or drugs for untreated diseases. Cover design by Ashmi Rodrigues. More information can be found in the Review by Ashmi Rodrigues, Lou Rocard and Roba Moumné.