Additional Active Site Research Articles

Synthesis of CdS QDs/NH2-Nb2O5 via electrostatic self-assembly method for highly efficient photocatalytic removal of NO and synchronous inhibition of NO2

A two-step electrostatic self-assembly method was used to first graft –NH2 groups onto the Nb2O5 followed by loading of CdS QDs onto the NH2-Nb2O5 to obtain CdS/NH2-Nb2O5. The performance of the samples under visible light was evaluated under simulated conditions of 25 °C and varying relative humidity (RHs). The results showed that with the increase of RH, the NO removal efficiency by CdS/NH2-Nb2O5 increased first and then decreased, reaching the maximum NO removal efficiency when RH = 50 %. The selectivity of NO2 on CdS/NH2-Nb2O5 (9.01 %) was significantly lower compared to that of Nb2O5 (24.44 %) and NH2-Nb2O5 (19.72 %). The introduction of –NH2 groups and CdS QDs significantly enhanced visible light absorption and improved the separation efficiency of photogenerated charge carriers. In-situ DRIFTS analysis revealed that Cd2+ served as an additional active site for NO adsorption. Furthermore, CdS had a relatively negative conduction band position, which was conducive to the generation of O2–, further inhibiting the generation of NO2. This work provides a new approach to the design and preparation of catalysts for photocatalytic oxidation of NO.

Theoretical evidence on pyridinic nitrogen in N, S-coordinated Co single atom catalyst as dominant active site promoting H2 cleavage, H diffusion, and hydrogenation activity

The limitation of isolated metal active sites in single atom catalysts (SAC) hinder their application in hydrogenation reactions, necessitating the creation of additional active site beyond the metal site. This study introduces pyridinic N and S atoms into the N/C sheet, optimally adjusting the local environment of the Co site. This adjustment synergistically enhances H2 activation, H diffusion, and promotes the hydrogenation of nitrobenzene into aniline. The sterically hindered Co acidic site and N basic site, known as frustrated Lewis pairs, in defect-containing Co-N3SN-def1 model cooperatively facilitate the highly efficient cleavage of the H2 molecule with a barrier of only 0.37 eV. The findings suggest that the pyridinic N site in the Co-N3SN-def1 model acts as a reservoir for *H, significantly contributing to the enhanced activity for the hydrogenation of nitrobenzene. The mechanism unveiled in this study offers valuable insights for designing efficient heterogeneous catalysts for target hydrogenation reactions.

Leveraging shape screening and molecular dynamics simulations to optimize PARP1-Specific chemo/radio-potentiators for antitumor drug design

PARP1 plays a pivotal role in DNA repair within the base excision pathway, making it a promising therapeutic target for cancers involving BRCA mutations. Current study is focused on the discovery of PARP inhibitors with enhanced selectivity for PARP1. Concurrent inhibition of PARP1 with PARP2 and PARP3 affects cellular functions, potentially causing DNA damage accumulation and disrupting immune responses. In step 1, a virtual library of 593 million compounds has been screened using a shape-based screening approach to narrow down the promising scaffolds. In step 2, hierarchical docking approach embedded in Schrödinger suite was employed to select compounds with good dock score, drug-likeness and MMGBSA score. Analysis supplemented with decomposition energy, molecular dynamics (MD) simulations and hydrogen bond frequency analysis, pinpointed that active site residues; H862, G863, R878, M890, Y896 and F897 are crucial for specific binding of ZINC001258189808 and ZINC000092332196 with PARP1 as compared to PARP2 and PARP3. The binding of ZINC000656130962, ZINC000762230673, ZINC001332491123, and ZINC000579446675 also revealed interaction involving two additional active site residues of PARP1, namely N767 and E988. Weaker or no interaction was observed for these residues with PARP2 and PARP3. This approach advances our understanding of PARP-1 specific inhibitors and their mechanisms of action, facilitating the development of targeted therapeutics.

Catalytic Effects of Active Site Conformational Change in the Allosteric Activation of Imidazole Glycerol Phosphate Synthase.

Imidazole glycerol phosphate synthase (IGPS) is a class-I glutamine amidotransferase (GAT) that hydrolyzes glutamine. Ammonia is produced and transferred to a second active site, where it reacts with N1-(5'-phosphoribosyl)-formimino-5-aminoimidazole-4-carboxamide ribonucleotide (PrFAR) to form precursors to purine and histidine biosynthesis. Binding of PrFAR over 25 Å away from the active site increases glutaminase efficiency by ∼4500-fold, primarily altering the glutamine turnover number. IGPS has been the focus of many studies on allosteric communication; however, atomic details for how the glutamine hydrolysis rate increases in the presence of PrFAR are lacking. We present a density functional theory study on 237-atom active site cluster models of IGPS based on crystallized structures representing the inactive and allosterically active conformations and investigate the multistep reaction leading to thioester formation and ammonia production. The proposed mechanism is supported by similar, well-studied enzyme mechanisms, and the corresponding energy profile is consistent with steady-state kinetic studies of PrFAR + IGPS. Additional active site models are constructed to examine the relationship between active site structural change and transition-state stabilization via energy decomposition schemes. The results reveal that the inactive IGPS conformation does not provide an adequately formed oxyanion hole structure and that repositioning of the oxyanion strand relative to the substrate is vital for a catalysis-competent oxyanion hole, with or without the hVal51 dihedral flip. These findings are valuable for future endeavors in modeling the IGPS allosteric mechanism by providing insight into the atomistic changes required for rate enhancement that can inform suitable reaction coordinates for subsequent investigations.

Synergistic Mo and S co-doping on NiSe2 electrodes for reduced kinetic barrier of water electrolysis

Hydrogen is an ideal energy carrier that can replace non-renewable fossil fuels in the future, and its production using electrochemical water splitting is one of the cleanest and best effective approaches. However, the commercialization of large-scale H2 production technologies requires earth-abundant electrocatalysts that exhibit Pt-like activity. This study reports, the dual doping of cations (Mo) and anions (S) into metallic NiSe2 using a green electrodeposition method to upgrade the H evolution reaction (HER) activity and durability of NiSe2, at the same time. Sulfur doping into NiSe2 provides an additional active site, whereas dual doping of Mo/S into NiSe2 boosts the HER kinetics and durability. Additionally, a NiSe2 matrix is doped with different concentrations of Mo/S and their HER performance is studied. A 5% Mo/S–NiSe2 has an optimized H∗ absorption energy, which is favorable for high HER performance. To drive the current densities of −10 and −100 mA cm−2, 5% Mo/S–NiSe2 electrode requires a small overpotentials of 89 and 222 mV, respectively, and the corresponding Tafel slope is 57 mV dec−1. The enhanced HER activity of Mo/S–NiSe2 is credited to the electronic structure adjustment, generation of a porous structure, and ample electrochemically active surface area owing to Mo/S dual doping. This strategy is promising for exploring new functional electrocatalysts for clean H2 production.

Heterostructured Mo2N–Mo2C Nanoparticles Coupled with N‐Doped Carbonized Wood to Accelerate the Hydrogen Evolution Reaction

Mo2C is a promising non‐precious hydrogen evolution reaction (HER) electrocatalyst. However, regulating the strong hydrogen adsorption characteristics of Mo2C and finding suitable support electrodes are essential processes before Mo2C can replace Pt to realize a sustainable hydrogen economy. Herein, the facile synthesis of heterostructured Mo2N–Mo2C nanoparticles on N‐doped carbonized wood (Mo2N–Mo2C/N‐CW) as a self‐supported electrode through carbonization and NH3 plasma treatment is demonstrated. The synergistic effects of heterostructured Mo2N–Mo2C and N‐CW with aligned microchannels provide enhanced catalytic activity, fast charge transfer kinetics, additional active site exposure, and rapid transport of the electrolyte and H2 bubbles, which improves the HER performance. Consequently, the Mo2N–Mo2C/N‐CW electrode exhibits superior HER performance with low overpotentials of only 79 and 311 mV to reach 10 and 500 mA cm−2 in an acidic solution, respectively. It also exhibits long‐term stability for 20 h in the high‐current‐density region (110 mA cm−2). The density functional theory (DFT) calculations at various sites reveal that the heterointerface of Mo2N and Mo2C promoted the catalytic activity by optimizing the adsorption/desorption of hydrogen.

Identification of DEDD- and PHP-Superfamilies of Proofreading Exonucleases in the Acidic Protein Subunit PA of RNA Polymerase of Human Influenza Viruses

RNA polymerase from human influenza viruses A, B and C is a heterotrimric enzyme, made up of three different subunits. It performs the crucial function of both genome replication as well as transcription. One of the RNA polymerase subunits, the polymerase acidic protein subunit (PA), is suggested to function as an endonuclease in a ‘cap-snatching’ mechanism, unique to influenza viruses. However, by multiple sequence alignment (MSA) analysis, it was found that the PA subunits of the polymerases do harbour typical proofreading (PR) DEDD-superfamily of exonuclease active site in all three viruses. However, in human influenza A virus, an additional putative PR exonuclease active site amino acids belonging to Polymerase-Histidinol Phosphatase (PHP)-superfamily are identified. The identified active site amino acids data are in close agreement with the similar DEDD- and PHP-superfamilies of PR exonucleases, already reported from both DNA-dependent RNA polymerases (DdRps) and RNA-dependent RNA polymerases (RdRps) from prokaryotes, eukaryotes and RNA viruses. The putative PHP–family PR exonuclease active site, identified by MSA analysis, is also in close agreement to the already reported PHP–family of PR exonuclease active sites from DdDps of replicases and pol X polymerases of the bacterial kingdom. Only in the pandemic causing human influenza A virus, the putative PHP-family PR exonuclease domain is found along with the DEDD-family PR exonuclease domain.

Time-dependent oxidation of graphite and cobalt oxide nanoparticles as electrocatalysts for the oxygen evolution reaction

• Co 3 O 4 /G OX was synthesized via a facile hydrothermal method for the OER. • Co 3 O 4 /G OX-10 catalyst showed the lowest overpotential of 250 mV at 10 mA cm −2 . • The optimal catalyst exhibited higher specific activity and turnover frequency. • Demonstrated improved electrical conductivity and small charge transfer resistance. • The optimal catalyst Exhibited excellent stability and durability. Water splitting is a promising way of producing hydrogen, but a highly efficient and durable electrocatalyst to accelerate the oxygen evolution reaction (OER) is required. In this study, we report cobalt oxide (Co 3 O 4 ) and oxidized graphite (G OX ) synthesized by a simple hydrothermal method to prepare a catalyst (Co 3 O 4 /G OX ) for the OER. Time-dependent oxidation of graphite (G) and Co 3 O 4 nanoparticles was observed by physical and electrochemical studies. The optimal catalyst (Co 3 O 4 /G OX-10 ) demonstrated the best catalytic OER performance with the lowest overpotential of 250 mV to reach 10 mA cm −2 and a small Tafel slope of 67 mV dec -1 , which is substantially smaller than that of pristine Co 3 O 4 and Co 3 O 4 /G. An efficient synergistic effect between Co 3 O 4 and G OX in the composite catalyst was observed compared to the individual catalysts. The optimal catalyst exhibited high specific activity (1.543 mA cm −2 ) and turnover frequency (0.474 s −1 ) compared to the other catalysts in this study. The high catalytic performance of the catalyst is attributed to the presence of oxygen functional groups, which induced a high electrochemical surface area, additional active site exposure, fast electron transfer, and enhanced dispersion of the catalyst. Thus, the synthesized Co 3 O 4 /G OX-10 catalyst can replace noble metals as an efficient OER electrocatalyst.

Functionalized Carbon Nanotubes Supported 3D Zinc/Cobalt Oxide as an Efficient Electrocatalyst for Oxygen Evolution Reaction

In this study, we developed 3D zinc oxide (ZnO) and cobalt oxide (Co3O4) supported by functionalized carbon nanotubes (O-CNT) to form a catalyst (ZnO/Co3O4@O-CNT) for oxygen evolution reaction (OER). The catalyst improved catalytic OER performance with the lowest overpotential of 260 mV to reach 10 mA cm−2 and a small Tafel slope of 79 mV dec−1, which is smaller than that of ZnO/Co3O4 and O-CNT. The catalyst exhibited fast electron transfer and high electrical conductivity owing to the O-CNT that acted as a conducting support, and the introduction of ZnO synergistically enhanced the OER activity of the synthesized catalyst. The specific activity and turnover frequency of the ZnO/Co3O4@O-CNT catalyst at an overpotential of 400 mV were 0.130 mA cm−2 and 2.45 s−1, respectively, which are considerably higher than those of pristine ZnO/Co3O4 (0.024 mA cm−2, 0.23 s−1) and O-CNT (0.012 mA cm−2, 0.03 s−1). The high catalytic performance of the catalyst is attributed to the presence of oxygen functional groups, which induced a high electrochemical surface area, additional active site exposure, fast electron transfer, and enhanced dispersion of the catalyst. Thus, the synthesized ZnO/Co3O4@O-CNT catalyst can be a good candidate as an alternative to high-cost noble metals for OER performance.

Kinetic model of ethylene oxidation in the presence of both ethylene dichloride (1,2-dichloroethane) and carbon dioxide over a highly selective silver catalyst

Experiments were conducted to obtain the kinetic model of ethylene oxidation over a commercial highly selective catalyst αAl2O3/Ag-Cs-Re, for the first time. A gas mixture of 4.15–7.5% O2, 24.23% C2H4, 0–3.464% CO2, 0.56 ppm C2H4Cl2 and N2 at 17.4 bar and 208–240 °C was deployed, similar to that in industry. An adsorbed atomic oxygen and a gaseous ethylene molecule through modified or original Eley-Rideal mechanisms were responsible for both the partial and complete oxidation of ethylene. The partial oxidation engaged an additional uncovered active site in surface reaction compared to the complete oxidation. The surface reaction was the rate-limiting step under the experimental conditions. The proposed model is in remarkable agreement with the experimental data. The addition of CO2 to the feed was proved detrimental to the EO selectivity, only suppressing the EO production rate. Temperature raise was much in favor of the CO2 production rate, decreasing the EO selectivity.

Cg10062 Catalysis Forges a Link between Acetylenecarboxylic Acid and Bacterial Metabolism.

The reliance of biocatalysis on plant-derived carbon for the synthesis of fuels and chemicals places it in direct competition with food production for resources. A potential solution to this problem is development of a metabolic link between alternative carbon sources and bacterial metabolism. Acetylenecarboxylic acid, which can be synthesized from methane and carbon dioxide, could enable this connection. It was previously shown that the enzyme Cg10062 catalyzes hydration of acetylenecarboxylate to afford malonate semialdehyde. Subsequent hydration-dependent decarboxylation to form acetaldehyde (81%), which was also observed, limits its biocatalytic usefulness. Several Cg10062 variants including E114Q and E114D do not catalyze decarboxylation and provide malonate semialdehyde as the sole product, albeit with substantially reduced catalytic activity. To identify an efficient enzyme capable of catalyzing acetylenecarboxylate hydration without decarboxylation, we undertook a mechanistic investigation of Cg10062 using mutagenesis, kinetic characterization, and X-ray crystallography. Cg10062 is a member of the tautomerase superfamily of enzymes, characterized by their β-α-β protein fold and an N-terminal proline residue situated at the center of the enzyme active site. Along with Pro-1, five additional active site residues (His-28, Arg-70, Arg-73, Tyr-103, and Glu-114) are required for Cg10062 activity. Incubation of crystals of four catalytically slow variants of Cg10062 with acetylenecarboxylate resulted in atomic resolution structures of Pro-1 bound to a complete set of intermediates, fully elaborating the detailed mechanism of the enzyme and establishing the process to involve covalent catalysis. Further, the intermediate-bound E114D structure explains the mechanism governing decarboxylation suppression. Together, these studies provide the most detailed picture of the catalytic mechanism of a tautomerase enzyme to date.

Breaking the Scaling Relations in Oxygen Reduction Reaction on MoOy/Pt(CuNi)x Catalyst Toward Enhanced Activity

In recent years, density function theory (DFT) calculations have indicated that the trends in oxygen reduction reaction (ORR) activity of various catalysts can be correlated to the energetics of some key reaction intermediates, which oftentimes leads to a specific trend, namely “volcano plot” where the catalytic activity rises and falls as the absorption free energies of the intermediates change.1 More importantly, researchers found out the absorption free energies of the three species are strongly correlated, which implies the difficulty of optimizing the absorption free energies of the three independently.1,2 This finding suggests that reduction of the energy barrier for one reaction step will presumably lead to an increase for another.2–4 There are several proposed strategies to circumvent the absorption free energy scaling relations, such as N, S-doping,5 introducing additional absorption site,6,7 strain effect,8 etc. Of all the strategies, the introduction of reducible transition oxides has recently shown the great potential in tailing adsorption energies of reaction intermediates on the active sites.In this work, a group of Pt(CuNi)x ternary alloy nanoparticles on carbon support were synthesized using a modified solid-state chemistry method (x = 0.33, 0.5, 0.66, 1, 1.5, 2, 3). It is believed that alloying Pt with transition metals could shift the d-band center of the alloy downwards, which causes lower absorption energy of the intermediate oxygenated species. By changing the composition of Pt(CuNi)x alloy, we could essentially tune the reaction intermediate absorption energy. Interestingly, the ORR catalytic activity test shows as x (i.e., the content of Cu and Ni) increased, the intrinsic area-specific activity (SA) increased, then deceased, exhibiting a “volcano trend” where the Pt(CuNi)0.66 peaked with a SA of 4.15 mA cm-2 Pt. Since the catalytic activity can be correlated with the reaction intermediate absorption energy, the volcano trend can be explained by Pt(CuNi)0.66 alloy having the most suitable intermediate absorption energy compared to alloys with other compositions. However, the scaling relations between oxygenated intermediate species (*O, *OH, and *OOH) limited the further improvement of catalytic activity. Thus, the deposition of molybdenum oxide as an additional active site was proposed to break the scaling relations and improve further beyond the volcano peak. After the typical synthesis of Pt(CuNi)x catalyst, molybdenum hexacarbonyl (Mo(CO)6) was deposited onto the fresh Pt(CuNi)x catalyst and reduced to metallic Mo. The MoOy/Pt(CuNi)x catalyst was obtained by oxidizing Mo to MoOy in the air. The X-ray photoelectron spectroscopy (XPS) analysis reveals that the MoOy consisted of a mixture of MoO3 and MoO2. The electrochemically active area (ECSA) value for MoOy/Pt(CuNi)0.66 decreased from 32.1 to 24.0 m2 g-1 Pt, suggesting a 25% coverage of the metal alloy surface by MoOy. The SA of MoOy/Pt(CuNi)0.66 increased by roughly 14%, from 4.4 to 5.0 mA cm-2 Pt. The SA enhancement was observed for all synthesized MoOy/Pt(CuNi)x catalyst causing the activity volcano plot to shift upwards, which provides strong experimental evidence the activity limit imposed by scaling relations was broken by the deposition of MoOy. The synergistic effect between Pt surface and metal oxides provides several benefits: (i) providing additional active sites for reaction intermediate absorption and reducing the intermediate coverage by enabling spillovers of intermediates between Pt and metal oxide surface.6,7,9 The dual-site cascade oxygen reduction mechanism was reported in detail previously by our group.6 (ii) facilitating O2 absorption and bond breakage by tailoring the electronic structure of adjacent Pt sites.7,10 Therefore, the utilization of reducible transition oxide has shown great potential to overcome the scaling rations to achieve higher ORR activity on Pt-based catalysts.Reference A. Kulkarni, S. Siahrostami, A. Patel, and J. K. Nørskov, Chem. Rev., 118, 2302–2312 (2018).J. K. Nørskov et al., J. Phys. Chem. B, 108, 17886–17892 (2004).Z. W. Seh et al., Science (80-. )., 355, eaad4998 (2017).T. Z. H. Gani and H. J. Kulik, ACS Catal., 8, 975–986 (2018).Y.-Y. Wang, D.-J. Chen, T. C. Allison, and Y. J. Tong, J. Chem. Phys., 150, 41728 (2019).X. Shen et al., J. Am. Chem. Soc., 141, 9463–9467 (2019).W. Gao, Z. Zhang, M. Dou, and F. Wang, ACS Catal., 9, 3278–3288 (2019).A. Khorshidi, J. Violet, J. Hashemi, and A. A. Peterson, Nat. Catal., 1, 263–268 (2018).Z. Awaludin, J. G. S. Moo, T. Okajima, and T. Ohsaka, J. Mater. Chem. A, 1, 14754–14765 (2013).Y. Lu, Y. Jiang, X. Gao, X. Wang, and W. Chen, J. Am. Chem. Soc., 136, 11687–11697 (2014). Figure 1

Utilization of the Coffee Ground-Derived Hard Carbon and Enhancement of Its Electrochemical Performance Via Sulfur Doping

Waste reduction and recycling performance in global economic and ecologic spheres are beginning to take shape every year. Undoubtedly, a particular attention is being devoted to the utilization of biomass-derived products for battery fabrication. It is significant to note that a selection of relevant biomass material, possessing a high and stable capacity (~300 mAh/g) within 200 cycles is a challenging part, becoming the main objective of the research project.In this context, coffee ground derived anode material for Sodium-ion battery (SIB) preserved a semi-stable structure with intergranular and microcracks due to the successive thermal treatments. Hydrothermal conversion processes acts as a significant part of the thermal conversion from coffee ground to hard carbon due to the continuous re-condensation reactions, allowing fabricating low surface area and blocked pores. Doping hard carbon with S improved electrochemical performance by achieving higher capacity than undoped material. The sulfur doped carbonized material has a unique porous structure that increased specific surface area and provided additional active site for sodium ion adsorption. Subsequently, further investigation will be focused on enhancement of hard carbon’s pores. Acknowledgments This work was supported by the Ministry of Education and Science of the Republic of Kazakhstan Grant (AP09259165), “Utilization of the biowaste-derived carbon and enhancement of its electrochemical performance via doping”.

Insight into the effects of dislocations in nanoscale titanium niobium oxide (Ti2Nb14O39) anode for boosting lithium-ion storage

Defect engineering through induction of dislocations is an efficient strategy to design and develop an electrode material with enhanced electrochemical performance in energy storage technology. Yet, synthesis, comprehension, identification, and effect of dislocation in electrode materials for lithium-ion batteries (LIBs) are still elusive. Herein, we propose an ethanol-thermal method mediated with surfactant-template and subsequent annealing under air atmosphere to induce dislocation into titanium niobium oxide (Ti2Nb14O39), resultant nanoscale-dislocated-Ti2Nb14O39 (Nano-dl-TNO). High-resolution transmission electron microscope (HRTEM), fast Fourier transform (FFT), and Geometrical phase analysis (GPA) denote that the high dislocation density engraved with stacking faults forms into the Ti2Nb14O39 lattice. The presence of dislocation could offer an additional active site for lithium-ion storage and tune the electrical and ionic properties of the Ti2Nb14O39. The resultant Nano-dl-TNO delivers superior rate capability, high specific capacity, better cycling stability, and making Ti2Nb14O39 a suitable candidate among fast-charging anode materials for lithium-ion batteries. Moreover, In-situ High-resolution transmission electron microscope (HRTEM) and Geometrical phase analysis (GPA) evinces that the removal of the dislocated area in the Nano-dl-TNO leads to the contraction of the lattice, alleviation of the total volume expansion, causing the symmetrization and preserves structural stability. The present findings and designed approach reveal the rose-colored perspective of dislocation engineering into mixed transition metal oxides as next-generation anodes for advanced lithium-ion batteries and all-solid-state lithium-ion batteries.

Surface Mechanism of Fe3+ Ions on the Improvement of Fine Monazite Flotation With Octyl Hydroxamate as the Collector.

Froth flotation of fine minerals has always been an important research direction in terms of theory and practice. In this paper, the effect and mechanism of Fe3+ on improving surface hydrophobicity and flotation of fine monazite using sodium octyl hydroxamate (SOH) as a collector were investigated through a series of laboratory tests and detection measurements including microflotation, fluorescence spectrum, zeta potential, and X-ray photoelectron spectroscopy (XPS). Flotation tests have shown that fine monazite particles (−26 + 15 μm) cannot be floated well with the SOH collector compared to the coarse fraction (−74 + 38 μm). However, adding a small amount of Fe3+ to the pulp before SOH can significantly improve the flotation of fine monazite. This is because the addition of Fe3+ promotes the adsorption of SOH and greatly improves the hydrophobicity of the monazite surface. This can result in the formation of a more uniform and dense hydrophobic adsorption layer, as shown by the fluorescence spectrum and zeta potential results. From the XPS results, Fe3+ reacts with surface O atoms on the surface of monazite to form a monazite–Osurf–Fe group that acts as a new additional active site for SOH adsorption. A schematic model was also proposed to explain the mechanism of Fe3+ for improving surface hydrophobicity and flotation of fine monazite using octyl hydroxamate as a collector. The innovative point of this study is using a simple reagent scheme to float fine mineral particles rather than traditional complex processes.

Dynamic interactions in the l-lactate oxidase active site facilitate substrate binding at pH4.5

The crystal structure of l-lactate oxidase in complex with l-lactate was solved at a 1.33 Å resolution. The electron density of the bound l-lactate was clearly shown and comparisons of the free form and substrate bound complexes demonstrated that l-lactate was bound to the FMN and an additional active site within the enzyme complex. l-lactate interacted with the related side chains, which play an important role in enzymatic catalysis and especially the coupled movement of H265 and D174, which may be essential to activity. These observations not only reveal the enzymatic mechanism for l-lactate binding but also demonstrate the dynamic motion of these enzyme structures in response to substrate binding and enzymatic reaction progression.

Engineering nanointerface of molybdenum-based heterostructures to boost the electrocatalytic hydrogen evolution reaction

The heterostructure can remarkably boost the HER activity contributed by the re-distribution of interface charge and the resulting modification of interface hydrogen adsorption behavior. Rational heterostructure-design in electrocatalysts represents a promising approach toward high performance in the electrocatalytic hydrogen evolution reaction (HER). In specific, optimizing the H adsorption behavior at the surface/interface of heterostructure is of key importance to improve the catalytic performance. Herein, we demonstrate the construction of a heterostructure from a well-defined oxygen-bridged Co/Mo heterometallic zeolitic imidazolate framework (MOZ) as an efficient electrocatalyst for HER. The optimized hybrid exhibits high catalytic activity and stability in electrolytes with a wide pH range. Detailed XPS, XAS and theoretical studies reveal that the regulation of metal species can tailor the lattice of Mo 2 C within the hybrid and induce the formation of defect sites, which could not only induce surface charge transfer between the atoms and provide an additional active site, but also affect the H adsorption behavior at the interface of a heterostructure. This work provides an effective strategy to design a heterostructure with tailored active sites for energy conversion.

Abstract MP11: Aldosterone Synthase Structure With Cushing’s Disease Drug Osilodrostat Provides Clues For Treatment Of Primary Aldosteronism

Primary aldosteronism, the major form of secondary hypertension, often leads to cardiac disease. It develops due to excess steroid hormone aldosterone produced by aldosterone synthase, also known as cytochrome P450 11B2. CYP11B2 is 93% identical to cortisol-producing CYP11B1, which makes it difficult to design drugs specifically targeting CYP11B2. Osilodrostat (LCI699, Isturisa®) was initially developed as CYP11B2 inhibitor, but due to higher potency for CYP11B1 is now the first FDA-approved drug for CYP11B1-mediated Cushing’s disease. Thus, there is still no effective therapeutic option targeting CYP11B2 for primary aldosteronism. To determine aspects of the CYP11B2/osilodrostat interaction that could be improved to design a more selective CYP11B2 inhibitor, this project took a structure/function approach. First, osilodrostat affinity to CYP11B2 was examined using UV/vis spectroscopy. Osilodrostat induced a spectral change typical of ligand nitrogen coordination to the catalytic heme iron, establishing the binding location and mode, and revealed high CYP11B2 affinity. X-ray crystallography was used to solve the structure of CYP11B2 bound to osilodrostat. Consistent with the spectral analysis, osilodrostat binds in the active site with its imidazole nitrogen coordinating the heme iron. Additional interactions occur with the osilodrostat fluorinated benzonitrile. Osilodrostat binding was compared with that of its analog fadrozole to both CYP11B enzymes. CYP11B2 binding of osilodrostat is similar to (R) -fadrozole, but the fluorination of osilodrostat mediates additional active site interactions. Comparison with the previously-available CYP11B1 structure reveals CYP11B1 favors (S) -fadrozole due to distinct CYP11B active site architectures. These results suggest an opportunity to optimize inhibitor sterics to better discriminate between these two steroidogenic cytochrome P450 enzymes. Exploiting structural differences between the CYP11B enzymes should promote the design of therapeutics for the treatment of primary aldosteronism targeting CYP11B2, while reducing undesirable side effects due to off-target CYP11B1 inhibition.

Catalytic influence of light element incorporation in the lattice of palladium

The alloying of metals with foreign elements is a common approach for manipulating catalytic properties of active sites. For palladium-based catalysts, incorporation of light elements receives far less attention than Pd-metal alloys even though incorporated light element are catalytically significant. Due to their small size, light elements (H, B, C, and O) can occupy octahedral sites in Pd to form an interstitial phase, while palladium adjusts its lattice to accommodate the incorporation of larger light elements (S and P) to form distinct phases. The incorporated light element modifies the electronic structure of palladium, influencing the binding energy of substrates and reactive intermediates. Pd hydride and oxide often form in situ during hydrogenation or oxidation reactions, respectively, representing the (more, less) active phase of the catalyst. The reactive interstitial hydrogen dissolved in Pd tends to hydrogenate reactants completely and unselectively. Pd oxide can be the active phase for oxidation reactions, and the incorporated oxygen or oxygen vacancies may participate in the reaction directly. Incorporated light elements change geometric aspects of Pd ensembles, serving the role of site blocking, ensemble isolation, or serve as an additional active site, endowing Pd with bifunctional character. We review the synthetic approaches for incorporating light elements into the palladium lattice. We summarize the catalytic influence of light element incorporation into the palladium lattice with respect to electronic and geometric modification, in situ incorporated hydrogen and oxygen, and discuss the influence of light element incorporation into Pd on specific reactions (i.e., selective hydrogenation, oxidation, electrocatalysis, and CC cross coupling).

TiO2 anchored on MoS2 nanosheets based on molybdenite exfoliation as an efficient cathode for enhanced Cr (VI) reduction in microbial fuel cell

MoS2 nanosheet-decorated TiO2 nanocomposites were prepared via facile liquid-phase exfoliation of natural molybdenite combined with in situ hydrolysis route. These materials were used as a photocathode for the first time in microbial fuel cell (MFC) to reduce hexavalent chromium (Cr (VI)). Results showed the maximum power density of 1 wt% MoS2/TiO2-based MFC was 3.7 and 1.9 times higher than that of blank graphite and TiO2-based MFC, respectively. This MFC achieved 99.57% removal of Cr (VI) with a concentration of 20 mg L−1 within 8 h under visible light illumination at pH 2 and high degradation rate of 2.49 g m−3 h−1. The introduction of MoS2 nanosheets as a cocatalyst can expand the absorption of visible light, thereby leading to increased electronic participation in Cr (VI) reduction. Moreover, the appropriate amounts of MoS2 nanosheets also contribute to electrons migration and additional active site. The enhanced power output and Cr (VI) reduction efficiency of MFC can be attributed to the synergistic coupling between bioanode and MoS2/TiO2 photocathode. On the basis of its facile and scalable synthetic strategy as well as its stable and outstanding photoelectrocatalytic performance for MFC, this MoS2/TiO2 nanocomposite showed potential in the efficient treatment of wastewater.