The research teams led by Prof. ZHAO Zongbao K. and Prof. XUE Song from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences revealed the molecular bases of phosphite dehydrogenase (Pdh) variants binding to a non-natural cofactor nicotinamide cytosine dinucleotide (NCD). Their findings were published in ACS Catalysis.
　　Structural information and cofactor preference for phosphite dehydrogenase and variant. (Image by LIU Yuxue and FENG Yanbin)
　　The natural redox cofactor nicotinamide adenosine dinucleotide (NAD) is omnipresent in biological systems and involved in complex processes. It is challenging to predict the consequences of NAD intervention, largely because redox cofactors are involved in diverse metabolism and processes.
　　To enable selective controlling over a specific redox biochemistry, Prof. ZHAO proposed an approach by implementing non-natural redox cofactors previously. He created bioorthogonal redox systems consisting of malic enzyme mutants that strongly favored NCD (J. Am. Chem. Soc.). NCD-linked metabolic circuits were successfully devised for reductive carboxylation of pyruvate into malate by using phosphite as the electron donor, and the system achieved higher malate yield from glucose by the engineered Escherichia coli cells (ACS Catal.).
　　In this work, the researchers further improved NCD preference of Pdh variants and collected X-ray crystal structures of 3 enzymes in their cofactor-free and cofactor-bound forms. It was found that the cofactor-binding pocket of Pdh became more crowded upon introduction of large and polar amino acid residues.
　　Further, these Pdh variants formed new molecular interactions to favor NCD binding. Such a paradigmatic study should promote efforts to engineer other enzymes to favor non-natural redox cofactors, and eventually bring them into life by chemical and synthetic biologists.
　　This work was supported by National Natural Science Foundation of China and DICP, and dedicated to the 70th anniversary of DICP, CAS. (Text by LIU Yuxue and FENG Yanbin)

　　Supported single metal atoms have attracted broad interest for their demonstrated high efficiency in single metal catalysis. The preparation of such catalysts, however, remains challenging as the neutral metal atoms have a strong tendency to agglomerate to metal particles in typical preparations.
　　Researchers at the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences and the University of Delaware have reported a way to produce a colorless liquid reservoir of metal-like discrete platinum atoms. Their findings were published in Nature Communications.
　　Schematic illustration of (R1OR2)2Pt(0)Cl2H2
　　Platinum chloride salts are reduced by alcohols to single platinum metal atoms in an environmentally benign liquid surfactant. The individual Pt atoms are shielded by a mantle of hydrochlorides and docked in the liquid through abundant oxygen atoms. The preparation of the metal-like Pt atoms is scalable.
　　As a noble metal, metallic Pt nanoparticles on carbon or oxide supports are widely used in the petroleum refining and chemical industries due to their unique catalytic functions. "The reserve of Pt on earth is limited, and about 5.6 tons of Pt are consumed every year just in the silicone industry," said Z. Conrad Zhang, who led the research.
　　The researchers tested the catalytic performance of the liquid laden with Pt atoms. "We found that the electron-deficient Pt atoms in the liquid exhibited super-high activity and high selectivity for the reaction compared to known Pt catalysts," said LIU Kairui, a graduate student and lead author of the paper.
　　The docked discrete Pt atoms do not aggregate under reaction conditions - retaining high activity and staying colorless through repeated uses. "The high activity, selectivity and stability of this catalyst may dramatically reduce the amount of Pt consumed by the silicone industry and may be broadly applicable to other applications," Zhang said.
　　Although the liquid laden with the Pt atoms is stable at 120°C and remains clear for over six months on the shelf at ambient temperature, the researchers found that it turned dark due to aggregation of the Pt atoms when exposed to X-ray or electron beams often employed to characterize the Pt atoms. To resolve this challenge, the researchers turned to 195Pt nuclear magnetic resonance (NMR) spectroscopy as the tool which was found to provide unambiguous evidences for the produced Pt atoms.
　　"The NMR spectroscopic data of the liquid not only unambiguously showed the discrete nature of mononuclear Pt atoms, but also revealed only one carbon monoxide coordinated to a Pt atom," said Professor BAI Shi of the University of Delaware.
　　"We are expanding the depositories of various metal atoms in our current research. The successful synthesis of readily removable mantles of the Pt atoms in liquid phase may potentially enable atomically controllable fabrication of catalytic materials and metallic materials by design," said Zhang. (Text by LIU Kairui)

　　Recently, Prof. LIU Yang's group at the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences revealed the molecular mechanisms of JQ1 resistance in hepatocellular carcinoma. This study could provide the theoretical basis for improving the clinical response to anti-cancer agent. Their findings were published in J Exp Clin Cancer Res.
　　Sorafenib and lenvatinib are currently the standard first-line drug approved by the Food and Drug Administration (FDA) for advanced hepatocellular carcinoma (HCC). However, these drugs only improve overall survival for 3 months of HCC patients and the tumor responses are generally poor. Therefore, it is urgent to develop a new novel therapeutic drug for HCC treatment.
　　EGFR -I645L mutant constitutively activates MEK/ERK signal to attenuate FBXW7 mediated C-MYC ubiquitination though regulating phosphorylation of p-MYC-ser62 site. (Image by YIN Yalei and WANG Ting)
　　It was reported that JQ1, which is a specific and competitive inhibitor of bromodomain-containing protein 4 (BRD4), inhibited expression of c-Myc and induced cellular apoptosis, suggesting its great potential in HCC clinical treatment. However, the molecular mechanism of the sensitivity of HCC to JQ1 has not been understood yet.
　　"We uncovered a novel activating EGFR mutation-I645L in JQ1-insensitive HCC cells by using whole exome-sequencing (WES)" said LIU. "This mutant could constitutively activate MAPK pathway, leading to phosphorylation of C-Myc at ser62 site and enhanced stability of oncogenic MYC protein in JQ1 resistant cells." LIU added. Furthermore, the combination of JQ1 with either EGFR or ERK inhibitors significantly enhanced the anti-tumor effect of JQ1 in vitro and in vivo.
　　This study suggests that EGFR or MAPK status might be considered ahead of JQ1 therapy and great therapeutic value for HCC treatment.
　　The research was supported by the National Key Research and Development Program of China, National Natural Science Foundation of China grants, Innovation program of science and research from the DICP, CAS. (Text by TIN Yalei and WANG Ting)

　　Recently, Dr. ZHOU Yan and Prof. SHEN Wenjie at the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences and their collaborators identified the atomic structure of the catalytically active copper-ceria interface and proposed a copper bilayer model. Their findings were published in Nature Catalysis.
　　Because of their high natural abundance, low cost, and, more importantly, their unique electronic characteristics, copper catalysts have been industrially applied and fundamentally studied for several chemical reactions that are intimately relevant to energy.
　　Copper nanoparticles, dispersed on ceria, constitute a highly efficient catalyst system for the low-temperature water-gas shift reaction, which generates hydrogen, and CO/CO2 hydrogenation that yields methanol. The two processes are crucial for utilizing carbon resources.
　　The copper-ceria interface has been presumed responsible for the catalytic performance. However, direct identification and a quantitative description of the active sites, which directly interact with the reactive molecules during catalysis, remain challenging.
　　Atomic structure of the copper-ceria interface. (Image by ZHOU Yan)
　　"Our conclusions are based on the observation of tiny copper clusters by a combination of scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS), probing the interfacial bonding environment by in situ infrared (IR) spectroscopy, and rationalization by density functional theory (DFT) calculations," said Prof. SHEN.
　　"In studying the atomic structure of the catalytically active copper-ceria interface, we found the copper cluster consisted of a bottom layer of mainly Cu+ atoms bonded on the oxygen vacancies of ceria, and a top layer of Cu0 atoms coordinated with the underlying Cu+ atoms," Prof. SHEN added.
　　Moreover, the scientists found that the low-temperature water-gas shift reaction occurred at the copper-ceria interfacial perimeter via a site cooperation mechanism, by which the Cu+ site chemically adsorbs CO while the neighboring oxygen vacancy site dissociatively activates water. (Text by ZHOU Yan)

　　Single-atom catalysts (SACs) with atomically dispersed active metal centers on supports represent an intermediary between heterogeneous and homogeneous catalysis. Therefore, understanding the homogeneous catalysis prototype creates a great opportunity for designing SACs and developing related applications.
　　HUANG Yanqiang and colleagues in Prof. ZHANG Tao's research group at the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences recently developed a strategy to rationally design a single-atom catalyst for applications. The method involves creating single-atom active sites on supports based on homologous homogeneous prototypes. This process ensures the stability of the active sites and also preserves catalytic capability during the corresponding homogeneous processes.
　　The strategy is exemplified in the Ir-based catalysts for the catalytic transformation of CO2 to formate. The support in an SAC is similar to the ligands of a mononuclear metal complex in homogeneous catalysis. The surface atomic structure of the support behaves like a "chelator" of organic complexes toward single atom metal centers, and this function is directly related to the chemical bonding and electronic state of the active metal sites.
　　Accordingly, the design of a support having electron-donating functional groups, which imitates a mononuclear Ir pincer complex, is a key factor in the development of an Ir-based SAC for the catalytic transformation of CO2 to formate.
　　By developing a porous organic polymer with aminopyridine functionalities to construct Ir single-atom active sites analogous to the mononuclear Ir complexes (Fig. 1), this material exhibits superior activity relative to conventional nanoparticle catalysts during the hydrogenation of CO2 to formate under mild conditions. This represents the best performance yet for a heterogeneous conversion of CO2 to formate, while maintaining outstanding stability upon recycling.
　　Meanwhile, a catalytic mechanism similar to that over a homogeneous Ir catalyst was observed with this quasi-homogeneous Ir-based SAC. The present strategy provides a promising basis for the design of efficient SACs for use in present-day homogeneous chemical conversions, and serves to illustrate potential bridging between homogeneous and heterogeneous catalysis.
　　Fig. 1 A porous organic polymer with aminopyridine functionalities with Ir single atom active sites analogous to the mononuclear Ir pincer complexes was demonstrated. (Image by DICP)
　　Published in Chem, this work was supported by the National Key R&D Program of China, the Strategic Priority Research Program of the Chinese Academy of Sciences, and the National Natural Science Foundation of China. (Text by DICP)

　　Screen-printed devices show strength in numbers
　　Researchers in China have developed an easy way to make complicated arrays of microsupercapacitors that involves screen-printing them out of graphene ink. The simplicity and freedom offered by the approach will aid the development of new approaches to electronics and flexible devices.
　　Although semiconductor components continue to shrink, not all of the parts of modern gadgets are as easy to miniaturise. Capacitors and batteries are particularly challenging given that they are complex and discrete bundles of different materials. Microsupercapacitors, a tiny relative of both of these components, can do similar jobs.
　　Now, scientists at the Chinese Academy of Sciences have come up with a screen-printing method using a multi-purpose graphene ink that quickly lays down multiple microsupercapacitors in a variety of shapes and as complicated arrays. The ink combines graphene and carbon black, both of which are conductive, with a polymer binder in a solvent, although the simplicity of the mixture belies the difficulty in finding the right composition. ‘Preparing inks with suitable electrical, electrochemical and rheological properties was one of the biggest challenges for printable integrated microsupercapacitors,’ emphasises Zhong-Shuai Wu, one of the principal investigators on the project. Importantly, the ink shows shear-thinning behaviour, like ketchup: as it’s applied, the force causes it to lose its viscosity so it flows easily, but as soon as the force is removed, it thickens and keeps its shape.
　　They applied the graphene ink to a substrate, such as glass or flexible PET plastic, using a patterned screen as a stencil. The resulting pattern includes all of the conductive parts of the device. ‘The graphene-based ink can act as the microelectrodes, metal-free current collectors and interconnects, simultaneously,’ Wu notes. The ink dries for 12 hours, and then an electrolyte gel is applied and allowed to solidify for a further 12 hours, at which point the device is ready to use.
　　Because the entire structure of the device can be laid out in one step, very complicated designs can be made with ease. Although a single microsupercapacitor supplies less than one volt, the researchers were able to integrate 130 of them in series, giving an output of over 100 volts. ‘Micro-robots and soft actuators based on dielectric elastomer require hundreds and even thousands of volts,’ says Wu. ‘High voltage operation increases the scope and usefulness of microsupercapacitors,’ agrees Francesca Iacopi, head of the integrated nanosystems lab at the University of Technology Sydney in Australia.
　　The supercapacitors are incredibly flexible. (Image by Royal Society of Chemistry)
　　The devices are also flexible, if they’re printed on a flexible substrate, which should make them compatible with wearable electronics. ‘The versatility and low cost of this screen-print approach could be a plus in the wearable systems that are disposable, which is what most of the external health monitoring and other wearable systems are meant to be,’ says Iacopi. ‘I believe microsupercapacitors on flexible substrates like these would be particularly promising to support the area of wearable systems for health monitoring, for example sensors placed on skin and eyes.’
　　The investigators are keen use their method to make more complete devices, by including components that can harvest energy and store it in the microsupercapacitors, or put that stored energy to use. They also hope to use new electrolytes to increase the voltage each capacitor can provide, and improve the total energy a device can store. (Chemistry World)