Insights into the Effect of Sulfur Incorporation into Tungsten Diphosphide for Improved Hydrogen Evolution Reaction.

Exploring the highly active and stable nonprecious metal electrocatalysts is particularly important for the advancement of water electrolysis, whereas it remains a challenge to efficiently improve the intrinsic electrocatalytic activity. Herein, we reasonably constructed a self-supporting nanosheet array material with sulfur incorporated into WP2. Because of the tunability of electronic configuration and the formation of partial metal phase sulfides, the optimized catalyst exhibits a low overpotential of 115 mV at 10 mA cm-2, along with superb durability over 24 h in acidic media. Furthermore, theoretical calculations reveal that sulfur substitution effectively manipulates the local electronic configuration of WP2, which reduces the interaction between the catalyst surface and hydrogen atoms, thus improving the intrinsic activity of the hydrogen evolution reaction. This work provides valuable insight into the rational fabrication of highly efficient flexible electrode materials based on resourceful electrocatalysts for electrochemical water splitting.

Metallic S-CoTe with Surface Reconstruction Activated by Electrochemical Oxidation for Oxygen Evolution Catalysis.

Developing highly active electrocatalysts toward oxygen evolution reaction (OER) is critical for the application of water splitting for hydrogen production and can further alleviate the energy crisis problem, but still remaining challenging. Especially, unlocking the catalytic site, in turn, helps design the available catalysts. Herein, the nanorod cobalt telluride with sulfur incorporation grown on a carbon cloth (S-CoTe/CC) as catalysts for OER, which displays extraordinary catalytic activity, is reported. Significantly, the in situ formed CoOOH species on the surface of S-CoTe merited from the structure evolution during the OER process serves as the active species. Furthermore, density functional theory calculations demonstrate that sulfur incorporation can tailor the electronic structure of active species and substantially optimize the free energy, accelerating the OER kinetics. This work provides an in-depth understanding of enhanced OER mechanism through foreign elements incorporating into precatalysts and is beneficial for the guiding design of more efficient catalysts.

Cryptic Sulfur Incorporation in Thioangucycline Biosynthesis.

Sulfur incorporation into natural products is a critical area of biosynthetic studies. Recently, a subset of sulfur-containing angucyclines has been discovered, and yet, the sulfur incorporation step is poorly understood. In this work, a series of thioether-bridged angucyclines were discovered, and a cryptic epoxide Michael acceptor intermediate was revealed en route to thioangucyclines (TACs) A and B. However, systematic gene deletion of the biosynthetic gene cluster (BGC) by CRISPR/Cas9 could not identify any gene responsible for the conversion of the epoxide intermediate to TACs. Instead, a series of in vitro and in vivo experiments conclusively showed that the conversion is the result of two non-enzymatic steps, possibly mediated by endogenous hydrogen sulfide. Therefore, the TACs are proposed to derive from a detoxification process. These results are expected to contribute to the study of both angucyclines and the utilization of inorganic sulfur in natural product biosynthesis.

An in vitro DNA phosphorothioate modification reaction.

Phosphorothioation (PT) involves the replacement of a nonbridging phosphate oxygen on the DNA backbone with sulfur. In bacteria, the procedure is both sequence- and stereo-specific. We reconstituted the PT reaction using purified DndCDE from Salmonella enterica and IscS from Escherichia coli. We determined that the in vitro process of PT was oxygen sensitive. Only one strand on a double-stranded (ds) DNA substrate was modified in the reaction. The modification was dominant between G and A in the GAAC/GTTC conserved sequence. The modification between G and T required the presence of PT between G and A on the opposite strand. Cysteine, S-adenosyl methionine (SAM) and the formation of an iron-sulfur cluster in DndCDE (DndCDE-FeS) were essential for the process. Results from SAM cleavage reactions support the supposition that PT is a radical SAM reaction. Adenosine triphosphate (ATP) promoted the reaction but was not essential. The data and conclusions presented suggest that the PT reaction in bacteria involves three steps. The first step is the binding of DndCDE-FeS to DNA and searching for the modification sequence, possibly with the help of ATP. Cysteine locks DndCDE-FeS to the modification site with an appropriate protein conformation. SAM triggers the radical SAM reaction to complete the oxygen-sulfur swapping.

Stabilization of Lead-Tin-Alloyed Inorganic-Organic Halide Perovskite Quantum Dots.

Recently, lead-tin-based alloyed halide perovskite quantum dots (QDs) with improved stability and less toxicity have been introduced. However, the perovskite QDs containing tin are still unstable and exhibit low photoluminescence quantum yields (PLQYs), owing to the presence of defects in the alloyed system. Here, we have attempted to introduce sulfur anions (S2-) into the host lattice (MAPb0.75Sn0.25Br3) as a promising route to stable alloyed perovskite QDs with improved stability and PLQY. In this study, we used elemental sulfur as a sulfur precursor. The successful incorporation of sulfur anions into the host lattice resulted in a highly improved PLQY (>75% at room temperature), which is believed to be due to a reduction in the defect-related non-radiative recombination centers present in the host lattice. Furthermore, we found that the emission property could be tuned between the bright green and cyan-bluish regions without compromising on color quality. This work invigorates the perovskite research community to prepare stable, bright, and color-tunable alloyed inorganic-organic perovskite QDs without compromising on their phases and color quality, which can lead to considerable advances in display technology.

Biosynthesis of antibiotic chuangxinmycin from Actinoplanes tsinanensis.

Chuangxinmycin is an antibiotic isolated from Actinoplanes tsinanensis CPCC 200056 in the 1970s with a novel indole-dihydrothiopyran heterocyclic skeleton. Chuangxinmycin showed in vitro antibacterial activity and in vivo efficacy in mouse infection models as well as preliminary clinical trials. But the biosynthetic pathway of chuangxinmycin has been obscure since its discovery. Herein, we report the identification of a stretch of DNA from the genome of A. tsinanensis CPCC 200056 that encodes genes for biosynthesis of chuangxinmycin by bioinformatics analysis. The designated cxn cluster was then confirmed to be responsible for chuangxinmycin biosynthesis by direct cloning and heterologous expressing in Streptomyces coelicolor M1146. The cytochrome P450 CxnD was verified to be involved in the dihydrothiopyran ring closure reaction by the identification of seco-chuangxinmycin in S. coelicolor M1146 harboring the cxn gene cluster with an inactivated cxnD. Based on these results, a plausible biosynthetic pathway for chuangxinmycin biosynthesis was proposed, by hijacking the primary sulfur transfer system for sulfur incorporation. The identification of the biosynthetic gene cluster of chuangxinmycin paves the way for elucidating the detail biochemical machinery for chuangxinmycin biosynthesis, and provides the basis for the generation of novel chuangxinmycin derivatives by means of combinatorial biosynthesis and synthetic biology.

Biosynthesis of antibiotic chuangxinmycin from

Chuangxinmycin is an antibiotic isolated from CPCC 200056 in the 1970s with a novel indole-dihydrothiopyran heterocyclic skeleton. Chuangxinmycin showed antibacterial activity and efficacy in mouse infection models as well as preliminary clinical trials. But the biosynthetic pathway of chuangxinmycin has been obscure since its discovery. Herein, we report the identification of a stretch of DNA from the genome of CPCC 200056 that encodes genes for biosynthesis of chuangxinmycin by bioinformatics analysis. The designated cluster was then confirmed to be responsible for chuangxinmycin biosynthesis by direct cloning and heterologous expressing in M1146. The cytochrome P450 CxnD was verified to be involved in the dihydrothiopyran ring closure reaction by the identification of seco-chuangxinmycin in M1146 harboring the gene cluster with an inactivated . Based on these results, a plausible biosynthetic pathway for chuangxinmycin biosynthesis was proposed, by hijacking the primary sulfur transfer system for sulfur incorporation. The identification of the biosynthetic gene cluster of chuangxinmycin paves the way for elucidating the detail biochemical machinery for chuangxinmycin biosynthesis, and provides the basis for the generation of novel chuangxinmycin derivatives by means of combinatorial biosynthesis and synthetic biology.

The versatile low-molecular-weight thiols: Beyond cell protection.

Low-molecular-weight (LMW) thiols are extensively involved in the maintenance of cellular redox potentials and the protection of cells from a variety of reactive chemical and electrophilic species. However, we recently found that the metabolic coupling of two LMW thiols - mycothiol (MSH) and ergothioneine (EGT) - programs the biosynthesis of the anti-infective agent lincomycin A. Remarkably, such a constructive role of the thiols in the biosynthesis of natural products has so far received relatively little attention. We speculate that the unusual thiol EGT might function as a chiral thiolation carrier (for modification) and a novel activator (for glycosylation) of sugar. Additionally, we examine recent evidence for LMW thiols (MSH and others) as sulfur donors of sulfur-containing natural products. Clearly, the LMW thiols have more diverse activities beyond cell protection, and more attention should be paid to the correlation of their functions with thiol-dependent enzymes.