The Conversion of UDP‐Glc to UDP‐Man: In Silico and Biochemical Exploration To Improve the Catalytic Efficiency of CDP‐Tyvelose C2‐Epimerases

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The Conversion of UDP-Glc to UDP-Man: In Silico and Biochemical Exploration To Improve the Catalytic Efficiency of CDP-Tyvelose C2-Epimerases

Promiscuous CDP-tyvelose 2-epimerase (TyvE) converts NDP-glucose to NDP-mannose. We present the sequence fingerprints that are indicative of this conversion in TyvE-like enzymes. Eleven TyvE-like enzymes were identified, and the top two wild-type candidates and a quadruple mutant were characterized. The improved catalytic efficiency of these enzymes might help the design of new nucleotide production pathways starting from a cheap sugar substrates like sucrose.


Abstract

A promiscuous CDP-tyvelose 2-epimerase (TyvE) from Thermodesulfatator atlanticus (TaTyvE) belonging to the nucleotide sugar active short-chain dehydrogenase/reductase superfamily (NS-SDRs) was recently discovered. TaTyvE performs the slow conversion of NDP-glucose (NDP-Glc) to NDP-mannose (NDP-Man). Here, we present the sequence fingerprints that are indicative of the conversion of UDP-Glc to UDP-Man in TyvE-like enzymes based on the heptagonal box motifs. Our data-mining approach led to the identification of 11 additional TyvE-like enzymes for the conversion of UDP-Glc to UDP-Man. We characterized the top two wild-type candidates, which show a 15- and 20-fold improved catalytic efficiency, respectively, on UDP-Glc compared to TaTyvE. In addition, we present a quadruple variant of one of the identified enzymes with a 70-fold improved catalytic efficiency on UDP-Glc compared to TaTyvE. These findings could help the design of new nucleotide production pathways starting from a cheap sugar substrate like glucose or sucrose.

New Insights into the Behaviour of Commercial Silicon Electrode Materials via Empirical Fitting of Galvanostatic Charge‐Discharge Curves

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New Insights into the Behaviour of Commercial Silicon Electrode Materials via Empirical Fitting of Galvanostatic Charge-Discharge Curves

The fast fading of silicon electrodes is a known issue preventing commercialization. Using empirical equations and electrochemical impedance spectroscopy, we isolate the lithiation phases of silicon and show that the capacity fade of commercial silicon electrodes is reversible and related to the iR drop of the cell.


Abstract

Silicon (Si) materials for use in Lithium ion batteries (LIBs) are of continued interest to battery manufacturers. With an increasing number of commercially available Si materials, evaluating their performance becomes a challenge. Here, we use an empirical fitting function presented earlier to aid in the analysis of galvanostatic charge-discharge data of commercial Si half-cells with relatively high loading. We find that the fitting procedure is capable of detecting dynamic changes in the cell, such as reversible capacity fade of the Si electrode. This fading is found to be due to the highly lithiated Li2Si Li3.5Si phase and that the behaviour is strongly dependent on the potential of this phase. EIS reveals that the Si electrode is responsible for the reversible behaviour due to progressive loss of Li+ leading to increasing resistance. SEM/EDX and XPS characterization are also employed to determine the origin of the irreversible resistance growth on the Si electrodes.

Metal Carbide Additives in Graphite‐Silicon Composites for Lithium‐Ion Batteries

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Metal Carbide Additives in Graphite-Silicon Composites for Lithium-Ion Batteries

Graphite-silicon composites for batteries: Molybdenum and Chromium Carbides are used as additives to stabilize graphite/silicon composites. Spark plasma sintering technology is used to sinter the electrode powders. The presence of molybdenum or chromium carbides promotes the performance of C/Si electrodes in lithium cells, improving the cycling stability compared to pristine graphite/silicon compounds.


Abstract

The pathway for improving lithium-ion batteries′ energy density strongly depends on finding materials with enhanced performance. Although great efforts have been done, on the anode-side, graphite is still the best choice. In the last decade, silicon elements are attracting growing attention as anode since their use can theoretically increase specific capacity of the negative electrode side. However, as the electrochemical mechanism involves the alligation of a large amount of Li, the silicon electrode experiences huge volume changes (more than 300 % of its initial volume), leading to fractures and pulverizations of the electrode. Herein, we propose for the first time using Molybdenum and Chromium Carbides as additive to stabilize graphite/silicon composites. Spark plasma sintering technology is used to sinter the electrode powders. We demonstrated that the presence of molybdenum or chromium carbides promotes the performance of C/Si electrodes, improving the cycling stability compared to pristine graphite/silicon electrodes.

Unravelling the Secrets of α‐Pyrones from Aspergillus Fungi: A Comprehensive Review of Their Natural Sources, Biosynthesis, and Biological Activities

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Aspergillus, one of the most product-rich and genetically robust genera, contains a diverse range of species with potential economic and ecological implications. Chemically, Aspergillus is one of the essential sources of polyketides, alkaloids, diphenyl ethers, diketopiperazines, and other miscellaneous compounds, displaying a variety of pharmacological activities. The α-pyrones are unsaturated six-membered lactones. Although α-pyrone has a small structure, it is responsible for the structural diversity of several natural and synthetic compounds and multiple biological activities. In this review, we have summarized approximately 178 α-pyrone containing metabolites derivatives identified/reported from terrestrial, marine, endophytic, and filamentous Aspergillus species, including their sources, biological properties, and biosynthetic pathways until mid-2023, for the first time. This review is the first to compile and analyze the available data on α-pyrone metabolites from Aspergillus, which could facilitate further research and innovation in this field. Additionally, it offers a valuable source of scaffolds for future bioactive drug development, as some of these metabolites have shown potent antimicrobial, anti-inflammatory, and anticancer effects. Therefore, this review has significant implications for the advancement of natural product chemistry, pharmacology, biotechnology, and medicine.

Metal‐free Covalent organic frameworks for Oxygen Reduction Reaction

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Oxygen reduction reaction (ORR) is the key reaction in metal air and fuel cells. Among the catalysts towards ORR, carbon-based metal-free catalysts are getting more attention because of their maximum atom utilization, effective active sites and satisfactory catalytic activity and stability. However, the pyrolysis synthesis of these carbons resulted in disordered porosities and uncontrolled catalytic sites, which hindered us to achieve the catalysts’ properties previously, and build the structure–property relationship at molecular level. Covalent organic frameworks (COFs) constructed with designable building blocks have been employed as metal free electrocatalysts towards oxygen reduction reaction (ORR) due to their controlled skeletons, tailored pores size and environments, and well-defined location and kinds of catalytic sites. In this concept article, the development of metal-free COFs for ORR is summarized, and different strategies including skeletons regulation, linkages engineering and edge-sites modulation to improve the catalytic selectivity and activity are discussed. Furthermore, this Concept provides prospective for design and construction high electrocatalysts based on the catalytic COFs.

Synthesis of Organic Optoelectronic Materials Using Direct C‐H Functionalization

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Small molecules and polymers with conjugated structures can be used as organic optoelectronic materials. These molecules have conventionally been synthesized by cross-coupling reactions; however, in recent years, direct functionalization of C-H bonds has been used to synthesize organic optoelectronic materials. Representative reactions include direct arylation reactions (C-H/C-X couplings, with X being halogen or pseudo-halogen) and cross-dehydrogenative coupling (C-H/C-H cross-coupling) reactions. Although these reactions are convenient for short-step synthesis, they require regioselectivity in the C-H bonds and suppression of undesired homo-coupling side reactions. This review introduces examples of the synthesis of organic optoelectronic materials using two types of direct C-H functionalization reactions. In addition, we summarize our recent activities in the development of direct C-H functionalization reactions using fluorobenzenes as substrates. This review covers the reaction mechanism and material properties of the resulting products.

Precise Construction of Cu‐Based Catalysts using Surface Molecular Modifiers for Electroreduction of CO2 to Multi‐Carbon Products

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Converting CO2 into valuable chemicals has been intensively explored in recent years. Benefited from the substantial cost reduction of renewable electricity, the electrochemical methods have been emerging as a potential means for CO2 capture and conversion. Recently, molecular tuning has been recognized as a powerful technique to modify catalyst’s surface and verified effective in improving CO2RR performance. However, there are few comprehensive and insightful reviews on molecularly modified Cu-based catalysts to precisely modulate the activity and selectivity of C2+ products in CO2 reduction. Herein, the development of CO2RR plausible reaction mechanisms is first introduced. The process and reaction pathways of the carbon-carbon coupling are briefly discussed. Four main aspects of the molecular tuning strategy of the CO2RR are described as the first coordination layer, second coordination layer, outer-layer, and confined effects. The understanding of the improved C2+ performance is demonstrated for molecularly modified Cu-based catalysts. The challenges and perspectives in this field are addressed to further inspire the disclosure of the fundamental understanding in CO2RR, the system optimization, advanced in situ and operando techniques, and integration of CO2 capture and conversion technology with high activity and selectivity for durable applications.