A new organic-inorganic hybrid open-framework molybdovanadate with mixed-valences of vanadium (V4+ /V5+ =4/3) and molybdenum (Mo5+ /Mo6+ =8/2) cations has been synthesized. The complex possesses the unique V/Mo ratio (7/10), fascinating 8-C topological network and 1D 4-MR channels (7.793 Å×6.699 Å). Importantly, its catalytic activities for the selective oxidation of benzyl alcohol to benzaldehyde (oxidant: H2 O2 , 30 wt %) have been well evaluated. The results indicated that it exhibited improved catalytic activities (conv.: 96.8 %) compared with the catalyst (Cpyr)5 PV2 Mo5 W5 O40 [conv.: 88.51 %, Cpyr=(C16 H32 C5 H4 N)+ )], high recyclability and structural stability. Moreover, the conversions and selectivities (conv.: 82.4-92.5 %; sele.: 91.5-95.7 %) of the substrates containing electron donating groups (-OH, -CH3 , -OCH3 and -Cl) were significantly higher than those of the substrate containing electron withdrawing group (-NO2 ) (conv. 67.4 %; sele.: 80.8 %). This is due to the fact that the -NO2 with a large Hammett substituent constant is not conducive to the generation of transition state products. The studies revealed the complex could act as a highly efficient heterogeneous catalyst in selective oxidation of benzyl alcohols. 

Improved catalytic performance toward selective oxidation of benzyl alcohols originated from new open-framework copper molybdovanadate with a unique V/Mo ratio.

Cyanobacteria are photosynthetic prokaryotes with strong potential to be used for industrial terpenoid production. However, the key enzymes forming the principal terpenoid building blocks, called short‐chain prenyltransferases (SPTs), are insufficiently characterized. Here, we examined SPTs in the model cyanobacteria Synechococcus elongatus sp. PCC 7942 and Synechocystis sp. PCC 6803. Each species has a single putative SPT (SeCrtE and SyCrtE, respectively). Sequence analysis identified these as type‐II geranylgeranyl pyrophosphate synthases (GGPPSs) with high homology to GGPPSs found in the plastids of green plants and other photosynthetic organisms. In vitro analysis demonstrated that SyCrtE is multifunctional, producing geranylgeranyl pyrophosphate (GGPP; C20) primarily but also significant amounts of farnesyl pyrophosphate (FPP, C15) and geranyl pyrophosphate (GPP, C10); whereas SeCrtE appears to produce only GGPP. The crystal structures were solved to 2.02 and 1.37 Å, respectively, and the superposition of the structures against the GGPPS of Synechococcus elongatus sp. PCC 7002 yield a root mean square deviation of 0.8 Å (SeCrtE) and 1.1 Å (SyCrtE). We also discovered that SeCrtE is co‐encoded in an operon with a functional GGPP phosphatase, suggesting metabolic pairing of these two activities and a putative function in tocopherol biosynthesis. This work sheds light on the activity of SPTs and terpenoid synthesis in cyanobacteria. Understanding native prenyl phosphate metabolism is an important step in developing approaches to engineering the production of different chain‐length terpenoids in cyanobacteria.

/pdf/molecular-characterization-of-cyanobacterial-short-chain-1ocnnlf3.pdf

Molecular characterization of cyanobacterial short‐chain prenyltransferases and discovery of a novel GGPP phosphatase

Iron-based (pre)catalysts have attracted enormous attention for various electrooxidation reactions due to the low cost, high abundance, and multiple accessible redox states of iron. Herein, a well-defined helical iron borophosphate (LiFeBPO) is developed as an electro(pre)catalyst for the oxygen evolution reaction (OER) and selective alcohol oxidation. When deposited on nickel foam (NF), LiFeBPO exhibits an exceptional OER performance at ambient conditions attaining a current density of 100 mA cm−2 at ≈276 mV overpotential in 1 m KOH. Notably, this anode sustains durable alkaline water electrolysis at 500 mA cm−2 for over 330 h under industrial conditions (6 m KOH and 85 °C). In –situ and ex situ investigations reveal a deep reconstruction of LiFeBPO during OER, which transforms into a 3D open porous skeleton assembled by ultrasmall, low-crystalline α-FeOOH nanoparticles (interfacing with NiOOH of NF). This structure contributes to exposing accessible surface active sites, as well as accelerating mass transport and bubble detachment. Moreover, this electrode also catalyzes the electrooxidation of alcohols (methanol, ethylene glycol, and glycerol) to formic acid (FA) with high selectivity and full conversion. This study provides promising solutions for designing suitable anodes for the simultaneous production of green hydrogen fuel and value–added FA from electrooxidation reactions. 

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/adfm.202303702

In Situ Reconstruction of Helical Iron Borophosphate Precatalyst toward Durable Industrial Alkaline Water Electrolysis and Selective Oxidation of Alcohols

Archaeal glycerophospholipids are the main constituents of the cytoplasmic membrane in the archaeal domain of life and fundamentally differ in chemical composition compared to bacterial phospholipids. They consist of isoprenyl chains ether-bonded to glycerol-1-phosphate. In contrast, bacterial glycerophospholipids are composed of fatty acyl chains ester-bonded to glycerol-3-phosphate. This largely domain-distinguishing feature has been termed the "lipid-divide". The chemical composition of archaeal membranes contributes to the ability of archaea to survive and thrive in extreme environments. However, ether-bonded glycerophospholipids are not only limited to extremophiles and found also in mesophilic archaea. Resolving the structural basis of glycerophospholipid biosynthesis is a key objective to provide insights in the early evolution of membrane formation and to deepen our understanding of the molecular basis of extremophilicity. Many of the glycerophospholipid enzymes are either integral membrane proteins or membrane-associated, and hence are intrinsically difficult to study structurally. However, in recent years, the crystal structures of several key enzymes have been solved, while unresolved enzymatic steps in the archaeal glycerophospholipid biosynthetic pathway have been clarified providing further insights in the lipid-divide and the evolution of early life. 

/pdf/the-catalytic-and-structural-basis-of-archaeal-2ca13gqy.pdf

The catalytic and structural basis of archaeal glycerophospholipid biosynthesis

A hemiterpene, isoprene, is commercially produced from crude oil refining processes. As a result of fossil fuel depletion, isoprene production process development is gaining attention from recombinant cyanobacteria and other microbial systems for its industrial and biofuel applications. In the present study, a fast-growing and CO2-tolerant cyanobacteria, Synechococcus elongatus UTEX 2973, is engineered with Pueraria montana isoprene synthase (IspS) at neutral site I (NSI) in the genome of S. elongatus UTEX 2973. Furthermore, to enhance isoprene production a key enzyme (isopentenyl diphosphate isomerase, IDI) of the methyl-D-erythritol 4-phosphate (MEP) pathway is also overexpressed at neutral site III (NSIII). Wild-type and recombinant strains of S. elongatus UTEX 2973 (UTEX IspS and UTEX IspS.IDI) are studied for growth and isoprene production in the presence of an inducer (IPTG) and/or inhibitor (alendronate). Alendronate is used for the inhibition of geranyl diphosphate synthase (CrtE), downstream of the MEP pathway that catalyzes dimethylallyl diphosphate/isopentenyl pyrophosphate (DMAPP/IPP) condensation in the recombinant UTEX 2973 strains. The docking studies on SeCrtE (CrtE of Synechcoccus elongatus PCC 7942) and alendronate as an inhibitor have revealed that alendronate binds more tightly than IPP in the cavity of SeCrtE, with a higher number of intermolecular interactions and energy. The UTEX IspS strain has shown isoprene production below the limit of detection in the presence of an inducer and/or inhibitor; however, production studies using UTEX IspS.IDI showed a maximum production of 79.97 and 411.51 µg/g dry cell weight (DCW) in a single day in the presence of an inducer only and an inducer along with an inhibitor, respectively. The UTEX IspS.IDI strain produced 0.41 mg/g DCW of cumulative isoprene in the presence of an inducer and 1.92 mg/g DCW in the presence of an inducer as well as an inhibitor during six days of production. The yield improvement of isoprene is observed as being 4.7-fold by using the inhibition strategy, which is used for the first time in the recombinant cyanobacterial system. The average productivities of isoprene obtained from UTEX IspS.IDI are observed to be 2.8 μg/g DCW/h in the presence of an inducer and 13.35 μg/g DCW/h in the presence of an inducer as well as an inhibitor. This study provides a basis for the process development and yield improvement in isoprene production using a novel inhibition strategy in fast-growing recombinant cyanobacteria. Recombinant strains and metabolic pathway inhibition studies can be used in future attempts to photosynthetically produce hemiterpenes.

/pdf/geranyl-diphosphate-synthase-crte-inhibition-using-3bq4ozld.pdf

Geranyl Diphosphate Synthase (CrtE) Inhibition Using Alendronate Enhances Isoprene Production in Recombinant Synechococcus elongatus UTEX 2973: A Step towards Isoprene Biorefinery

Cyanobacteria are photosynthetic prokaryotes that perform oxygenic photosynthesis. Due to their ability to use the photon energy of sunlight to fix carbon dioxide into biomass, cyanobacteria are promising hosts for the sustainable production of terpenoids, also known as isoprenoids, a diverse class of natural products with potential as advanced biofuels and high-value chemicals. However, the cyanobacterial enzymes involved in the biosynthesis of the terpene precursors needed to make more complicated terpenoids are poorly characterized. Here we show that the predicted type II prenyltransferase CrtE encoded by the model cyanobacterium Synechococcus sp. PCC 7002 is homodimeric and able to synthesize C20-geranylgeranyl pyrophosphate (GGPP) from C5-isopentenyl pyrophosphate (IPP) and C5-dimethylallyl pyrophosphate (DMAPP). The crystal structure of CrtE solved to a resolution of 2.7 A revealed a strong structural similarity to the large subunit of the heterodimeric geranylgeranyl pyrophosphate synthase 1 from Arabidopsis thaliana with each subunit containing 14 helices. Using mutagenesis, we confirmed that the fourth and fifth amino acids (Met-87 and Ser-88) before the first conserved aspartate-rich motif (FARM) play important roles in controlling chain elongation. While the WT enzyme specifically produced GGPP, variants M87F and S88Y could only generate C15-farnesyl pyrophosphate (FPP), indicating that residues with large side chains obstruct product elongation. In contrast, replacement of M87 with the smaller Ala residue allowed the formation of the longer C25-geranylfarnesyl pyrophosphate (GFPP) product. Overall, our results provide new structural and functional information on the cyanobacterial CrtE enzyme that could lead to the development of improved cyanobacterial platforms for terpenoid production.

/pdf/crystal-structure-of-geranylgeranyl-pyrophosphate-synthase-1u5r9bu9al.pdf

Crystal Structure of Geranylgeranyl Pyrophosphate Synthase (CrtE) Involved in Cyanobacterial Terpenoid Biosynthesis.

A novel 3D open-framework copper borovanadate with a unique crown-shaped anion [(VIVO)8(VVO)4B32O64(OH)8]12- and the largest ratio of Cu2+/borovanadate anions (6/1) has been successfully synthesized and systematically studied. The compound not only possesses high stability in a wide pH range of 3.2-10.8 (DMF solution), but also exhibits excellent catalytic activities for selective oxidation of sulfides.

A highly efficient heterogeneous catalyst for selective oxidation of sulfides derived from an open-framework copper borovanadate containing a unique crown-shaped anion.

A novel open-framework borate-rich cadmium borophosphate has been obtained by the boric acid reflux method. The compound exhibits a complicated network which is composed of CdO6 octahedra and interesting 1D...

Efficient Degradation of Reactive Brilliant Red on the First Open-Framework Borate-Rich Cadmium Borophosphate

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Crystal Structure of Geranylgeranyl Pyrophosphate Synthase (CrtE) Involved in Cyanobacterial Terpenoid Biosynthesis.

A highly efficient heterogeneous catalyst for selective oxidation of sulfides derived from an open-framework copper borovanadate containing a unique crown-shaped anion.

Efficient Degradation of Reactive Brilliant Red on the First Open-Framework Borate-Rich Cadmium Borophosphate