Iron Telluride-Decorated Reduced Graphene Oxide Hybrid Microspheres as Anode Materials with Improved Na-Ion Storage Properties

Transition-metal telluride materials are studied as the anode materials for Na-ion batteries (NIBs). The FeTe₂–reduced graphene oxide (rGO) hybrid powders (first target material) are prepared via spray pyrolysis and subsequent tellurization. The H₂Te gas treatment transforms the Fe₃O₄–rGO powders to FeTe₂–rGO hybrid powders with FeTe₂ nanocrystals (various sizes <100 nm) embedded within the rGO. The FeTe₂–rGO hybrid powders contain 5 wt % rGO. The Na-ion storage mechanism for FeTe₂ in NIBs is described by FeTe₂ + 4Na⁺ + 4e^–↔Fe + 2Na₂Te. The FeTe₂–rGO hybrid discharge process forms metallic Fe nanocrystals and Na₂Te by a conversion reaction of FeTe₂ with Na ions. The discharge capacities of the FeTe₂–rGO hybrid powders for the first and 80th cycles are 493 and 293 mA h g^–1, respectively. The discharge capacities of the bare FeTe₂ powders for the first and 80th cycles are 462 and 83 mA h g^–1, respectively. The FeTe₂–rGO hybrid powders have superior Na-ion storage properties compared to bare FeTe₂ powders owing to their high structural stability and electrical conductivity

The active site in the LacAB-Tag6P complex.

<p><b>A</b>, Surface representation of the active site showing the binding orientation of tagatose-6-phosphate in the pocket. <b>B</b>, The final 2Fo-Fc electron density map contoured at 1.0 σ and overlaid on the model for tagatose-6-phosphate and water molecules (red spheres) binding in the active site pocket of LacAB. <b>C</b>, Schematic showing the detailed binding mode of tagatose-6-phosphate (blue) in the active site. Dashed lines indicate hydrogen bondings and polar interactions, which are labeled with the interatomic distances in Å. Decorated arcs represent van der Waals interactions of less than 5.0 Å. Water molecules are shown as red circles. Residues of LacA are indicated by asterisks.</p

Crystal Structure and Substrate Specificity of _D-Galactose-6-Phosphate Isomerase Complexed with Substrates

<div><p>D-Galactose-6-phosphate isomerase from <i>Lactobacillus rhamnosus</i> (LacAB; EC 5.3.1.26), which is encoded by the tagatose-6-phosphate pathway gene cluster (<i>lacABCD</i>), catalyzes the isomerization of D-galactose-6-phosphate to D-tagatose-6-phosphate during lactose catabolism and is used to produce rare sugars as low-calorie natural sweeteners. The crystal structures of LacAB and its complex with D-tagatose-6-phosphate revealed that LacAB is a homotetramer of LacA and LacB subunits, with a structure similar to that of ribose-5-phosphate isomerase (Rpi). Structurally, LacAB belongs to the RpiB/LacAB superfamily, having a Rossmann-like αβα sandwich fold as has been identified in pentose phosphate isomerase and hexose phosphate isomerase. In contrast to other family members, the LacB subunit also has a unique α7 helix in its C-terminus. One active site is distinctly located at the interface between LacA and LacB, whereas two active sites are present in RpiB. In the structure of the product complex, the phosphate group of D-tagatose-6-phosphate is bound to three arginine residues, including Arg-39, producing a different substrate orientation than that in RpiB, where the substrate binds at Asp-43. Due to the proximity of the Arg-134 residue and backbone Cα of the α6 helix in LacA to the last Asp-172 residue of LacB with a hydrogen bond, a six-carbon sugar-phosphate can bind in the larger pocket of LacAB, compared with RpiB. His-96 in the active site is important for ring opening and substrate orientation, and Cys-65 is essential for the isomerization activity of the enzyme. Two rare sugar substrates, D-psicose and D-ribulose, show optimal binding in the LacAB-substrate complex. These findings were supported by the results of LacA activity assays. </p> </div

Substrate-specific binding of D-psicose and D-ribulose to LacAB.

<p><b>A</b> and <b>D</b>, The binding of D-psicose and D-ribulose, respectively, at the active site of LacAB is shown, including the amino acid residues and water molecules (red spheres). <b>B</b> and <b>E</b>, The final 2Fo-Fc electron density maps contoured at 0.8σ are overlaid on the models for D-psicose and D-ribulose. <b>C</b> and <b>F</b>, The binding modes of D-psicose and D-ribulose. The substrates are shown in blue. Dashed lines indicate hydrogen bondings and polar interactions, which are labeled with the interatomic distances in Å. Decorated arcs represent van der Waals interactions of less than 5.0 Å. Water molecules are shown as red circles.</p

Schematic of the reaction catalyzed by LacAB and alignment of LacA, LacB, and RpiB sequences.

<p><b>A</b>, Galactose-6-phosphate (Gal6P) is converted to tagatose-6-phosphate (Tag6P) by LacAB during lactose catabolism. <b>B</b>, Multiple sequence alignment of LacA and LacB from <i>Lactobacillus rhamnosus</i> (GenBank accession numbers ZP03210387 and ZP03210388, respectively), <i>Ec</i>RpiB from <i>Escherichia coli</i> (PDB ID 1NN4; NP418514), <i>Mt</i>RpiB from <i>Mycobacterium tuberculosis</i> (2VVP; YP006515902), and <i>Ct</i>RpiB from <i>Clostridium thermocellum</i> (3PH4; YP001038990). The sequences are for precursors, and the numbering is based on LacA. Highly conserved residues are shown in red type and boxed in blue; strictly conserved residues are shown on a red background. Secondary structure elements are indicated in pink for LacA and in green for LacB. Residues interacting directly with bound Taga6P are indicated with a triangle in pink (LacA) and green (LacB). The figure was prepared using ESPript [41].</p

<i>In silico</i> identification and screening of CYP24A1 inhibitors: 3D QSAR pharmacophore mapping and molecular dynamics analysis

<p>Vitamin D is a key signalling molecule that plays a vital role in the regulation of calcium phosphate homeostasis and bone remodelling. The circulating biologically active form of vitamin D is regulated by the catabolic mechanism of cytochrome P450 24-hydroxylase (CYP24A1) enzyme. The over-expression of CYP24A1 negatively regulates the vitamin D level, which is the causative agent of chronic kidney disease, osteoporosis and several types of cancers. In this study, we found three potential lead molecules adverse to CYP24A1 through structure-based, atom-based pharmacophore and e-pharmacophore-based screening methods. Analysis was done by bioinformatics methods and tools like binding affinity (binding free energy), chemical reactivity (DFT studies) and molecular dynamics simulation (protein–ligand stability). Combined computational investigation showed that the compounds NCI_95001, NCI_382818 and UNPD_141613 may have inhibitory effects against the CYP24A1 protein.</p

Eco-Friendly Composite of Fe₃O₄‑Reduced Graphene Oxide Particles for Efficient Enzyme Immobilization

A novel type of spherical and porous composites were synthesized to dually benefit from reduced graphene oxide (rGO) and magnetic materials as supports for enzyme immobilization. Three magnetic composite particles of Fe₃O₄ and rGO containing 71% (rGO-Fe₃O₄-M1), 36% (rGO-Fe₃O₄-M2), and 18% (rGO-Fe₃O₄-M3) Fe were prepared using a one-pot spray pyrolysis method and were used for the immobilization of the model enzymes, laccase and horseradish peroxidase (HRP). The rGO-Fe₃O₄ composite particles prepared by spray pyrolysis process had a regular shape, finite size, and uniform composition. The immobilization of laccase and HRP on rGO-Fe₃O₄-M1 resulted in 112 and 89.8% immobilization efficiency higher than that of synthesized pure Fe₃O₄ and rGO particles, respectively. The stability of laccase was improved by approximately 15-fold at 25 °C. Furthermore, rGO-Fe₃O₄-M1-immobilized laccase exhibited 92.6% of residual activity after 10 cycles of reuse and was 192% more efficient in oxidizing different phenolic compounds than the free enzyme. Therefore, these unique composite particles containing rGO and Fe₃O₄ may be promising supports for the efficient immobilization of industrially important enzymes with lower acute toxicity toward <i>Vibrio fischeri</i> than commercial pure Fe₃O₄ particles

Experimental design (coded variables) and results of CCD-RSM for xylanase-aided pretreatment of pulp.

<p>a – Temperature (°C); b – Enzyme Dose (U/mg); c – Retention time (min); d – Permanganate Number; e – Brightness (%ISO) of pulp after pretreatment; f – Yellowness (b*) of pulp after pretreatment.</p

Reduction in Acute Ecotoxicity of Paper Mill Effluent by Sequential Application of Xylanase and Laccase

<div><p>In order to reduce the ecotoxicity of paper mill, four different enzymatic pretreatment strategies were investigated in comparison to conventional chemical based processes. In strategy I, xylanase-aided pretreatment of pulp was carried out, and in strategy II, xylanase and laccase-mediator systems were used sequentially. Moreover, to compare the efficiency of <i>Bacillus stearothermophilus</i> xylanase and <i>Ceriporiopsis subvermispora</i> laccase in the reduction of ecotoxicity and pollution, parallel strategies (III and IV) were implemented using commercial enzymes. Conventional C_DE_OPD₁D₂ (C_D, Cl₂ with ClO₂; E_OP, H₂O₂ extraction; D₁ and D_2, ClO₂) and X/XLC_DE_OPD₁D₂ (X, xylanase; L, laccase) sequences were employed with non-enzymatic and enzymatic strategies, respectively. Acute toxicity was determined by the extent of inhibition of bioluminescence of <i>Vibrio fischeri</i> with different dilutions of the effluent. Two-fold increase was observed in EC₅₀ values for strategy I compared to the control process. On the other hand, sequential application of commercial enzymes resulted in higher acute toxicity compared to lab enzymes. In comparison to the control process, strategy II was the most efficient and successfully reduced 60.1 and 25.8% of biological oxygen demand (BOD) and color of effluents, respectively. We report for the first time the comparative analysis of the ecotoxicity of industrial effluents.</p></div

Experimental design (coded variables) and results of CCD-RSM for laccase-aided pretreatment of pulp.

<p>a – Retention Time (min); b – Enzyme Dose (U/mg); c – Mediator Concentration (%); d – Permanganate Number; e – Brightness (%ISO) of pulp after <i>C. subvermispora</i> laccase mediated pretreatment; f – Yellowness (b*) of pulp after <i>C. subvermispora</i> laccase mediated pretreatment.</p