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Structural materials with high strength-to-weight ratio are the candidate materials for future automotive applications. In this attempt, thick dissimilar AA6061/AA2014 alloys were welded by friction stir welding. This experiment aims at investigating the effect of polygonal hybrid pin profiles on structure–property relationship. The effect of tilt angle and tool offset on material flow at nugget zone was also investigated. The weld joint characterisation was done by optical microscopy, SEM and XRD to reveal the microstructure and constituent elements in the weldment. The weld profile produced by polygonal pin exhibits equiaxed fine grains at nugget zone. The characteristic study of tensile strength, micro-hardness and flexural strength was carried out. Optimum weld condition was found at a tool rotational speed of 900 rpm, weld speed of 20 mm/min, tilt angle of 1°, tool offset of 1.5 mm and with hybrid square pin profile. [ABSTRACT FROM AUTHOR]

□ Proton-induced X-ray emission (PIXE) was used to study submerged fermentation of ethanol from jaggery using Saccharomyces cerevisiae as the organism. The effect of CaCO3as a mineral source for the fermentation process was studied and its activity was monitored. A 3 MeV proton beam obtained from a tandem type pelletron accelerator was used for the multielemental analysis to characterize the calcium uptake in fermentation process. Along with the characterization of Ca, K, Fe, Cr, Co, Ni, Cu, and Zn were also identified in this fermentation process, which may be useful to interpret the various metabolic conditions and studying the impact of these elements. The rate of uptake of calcium by the organism was found to be highest at 14 mg/L supplementation, which was contributed to the final ethanol concentration of 57.8 g/L. A maximum uptake rate of 0.304 mg/L/hr was noticed for CaCO3at 14 mg/L supplementation. The present work demonstrates the suitability of PIXE for the determination of various elements in fermentation processes. [ABSTRACT FROM AUTHOR]

Modern life requires many different metal ions, which enable diverse biochemical functions. It is commonly assumed that metal ions' environmental availabilities controlled the evolution of early life. We argue that evolution can only explore the chemistry that life encounters, and fortuitous chemical interactions between metal ions and biological compounds can only be selected for if they first occur sufficiently frequently. We calculated maximal transition metal ion concentrations in the ancient ocean, determining that the amounts of biologically important transition metal ions were orders of magnitude lower than ferrous iron. Under such conditions, primitive bioligands would predominantly interact with Fe(II). While interactions with other metals in certain environments may have provided evolutionary opportunities, the biochemical capacities of Fe(II), Fe-S clusters, or the plentiful magnesium and calcium could have satisfied all functions needed by early life. Primitive organisms could have used Fe(II) exclusively for their transition metal ion requirements. [ABSTRACT FROM AUTHOR]

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The current study attempted to introduce nano-aluminium oxide (Al2O3) particles into ZE41 alloy via friction stir processing (FSP). The effect of these nano-Al2O3 particles on the mechanical and tribological characteristics of ZE41 alloy is investigated. The results of microstructural studies revealed the uniform distribution of Al2O3 particles and substantial grain refinement in the stir zone by FSP. Enhanced microhardness was observed in the processed region due to the grain refinement and the occurrence of regularly distributed Al2O3 particles. The wear resistance was also seen increased with the incorporation of the Al2O3 particles. Moreover, the effect of FSP parameters on the successful incorporation of nano-Al2O3 particles in ZE41 alloy without any defect is also realised. [ABSTRACT FROM AUTHOR]

This work focused on improving the weld quality and productivity of dissimilar friction stir welding of AA 7075-T6 and AA 2024-T3 aluminium alloys by controlling the process parameters of tool axial force, welding speed, tool offset, and rotational speed. A newly developed hybrid pentagonal tool is used for the fabrication of welds to enhance productivity. In this study, an RSM based on a central composite method is used for the design of experiments, optimisation, and data analysis. The result found that the ideal range of welding process parameters for 6-mm-thick AA7075-T6 and AA2024-T3 aluminium alloys by friction stir welding is to use a tool spindle rotational speed of 1178.51 rpm, an axial load of 7.78 KN, a traverse speed of 132.74 mm/min, and 0.958 mm tool offset towards the AA2024-T3 material side. Based on the UTS, a joint efficiency of 67.19% is achieved. It is observed that while increasing the value of FSW parameters like tool spindle rotational speed and traverse speed, the tensile strength and elongation values tend to increase drastically after further increasing those parameters, UTS and TE seem to decrease. [ABSTRACT FROM AUTHOR]

Organoids are three‐dimensional cell aggregates with near‐physiologic cell behaviors and can undergo long‐term expansion in vitro. They are amenable to high‐throughput drug screening processes, which renders them a viable preclinical model for drug development. The procedure of organoid‐based high‐throughput screening has been extensively employed to discover small‐molecule drugs, encompassing the steps of generating organoids, examining efficient drugs in organoid cultures, and data assessment. Compared to small molecules, peptides are more straightforward to synthesize, can be modified chemically, and demonstrate high target specificity and low cytotoxicity. Therefore, they have emerged as promising carriers to deliver drugs to disease‐associated targets and could be efficient therapeutic drugs for various diseases. To date, organoids have been used to evaluate the efficacy of certain peptide agents; however, no organoid‐based high‐throughput screening of peptide drugs has been reported. Given the advantages of peptide drugs, there is an urgent need to establish organoid‐based peptide high‐throughput screening platforms. In this review, we discuss the typical approach of screening small‐molecular drugs with the use of organoid cultures, as well as provide an overview of the studies that have incorporated organoids in peptide research. Drawing on the knowledge from small molecular screens, we explore the difficulties and potential avenues for creating new platforms to identify peptide agents using organoid models. [ABSTRACT FROM AUTHOR]

Impressioncreep (IC) tests were performed at three welded regions viz: nugget zone (NZ), thermo-mechanical affected zone (TMAZ) and heat affected zone (HAZ) at 326°C, 359°C and 378°C of furnace temperature and equivalent stresses of 24MPa, 28MPa and 32MPa respectively. The high temperature deformation properties were estimated by employing power law creep equation and the results were compared with the base material (BM). The rate controlling mechanism of IC process at each selected area and its correlation with the microstructural evolution throughout FSW and IC procedures were realised. The steady-state creep rate of NZ was estimated to be the highest and of BM was the lowest. The other creep parameters such as the stress exponents and the apparent activation energy for the IC process were calculated at each localised zones for the welded material and were compared with the BM. The creep deformation was found to be homogeneous at all the selected testing areas and was of dislocation type. Creep rate was found to be affected by the grain size and testing temperature. Detail microstructural analysis of the samples before and after the IC test was performed by optical microscope. [ABSTRACT FROM AUTHOR]

A new mononuclear cobalt(III)‐pentasulfido compound, [(L)Co(S5)] (3) has been synthesized by using a convergent redox reaction between elemental sulfur and two new cobalt(II)‐thiolato compounds, [(L)Co(SR)] (R=Ph, 2 a; 2,6‐Me2‐C6H4, 2 b), which in turn were synthesized from a dimeric cobalt(II) complex, [(L)2Co2]2+ (1). Compound 3 features a low‐spin, diamagnetic, Co(III) center with a coordinated pentasulfido (S52−) chain and has no precedence in the literature. Compound 3 is highly stable towards reduction with a potential of −1.36 V (vs. Cp2Fe+/Cp2Fe) and gives back 1 upon chemical/electrochemical reduction. Reaction of 3 with phosphines yields back 1 and phosphine sulfides, while protonation of the coordinated S52− chain in 3 leads to the formation of 1, elemental sulfur and H2S. Finally, transfer of the coordinated S52− chain in 3 to selected organic compounds, such as MeI, PhCH2Br and PhCOCl, for the generation of organopolysulfido compounds has been demonstrated. [ABSTRACT FROM AUTHOR]

Quorum sensing (QS) is enabled by the production of signalling molecules called autoinducers, whose presence in the environment modulates the behavior of bacterial populations. Autoinducer‐2 (AI‐2) is unique as it is recognized by different species of bacteria and fosters signalling across different species. To further understand QS mechanisms and to discover potential novel therapeutics based on the modulation of bacterial behavior many analogs have been synthesized. This review aims to provide a critical analysis of the state‐of‐the‐art of the synthesis of AI‐2 and its analogs. It serves as a non‐exhaustive consolidation of previous studies of analogs, focusing on the synthetic approaches and the structure‐activity relationship conclusions drawn after the analysis of the chemical libraries of the research groups involved in the field. This article is intended to be a strong foundation for the rational planning of synthetic strategies of analogs with specific bioactivities. [ABSTRACT FROM AUTHOR]

Root canal treatment is a treatment sequence for the infected pulp of a tooth which is intended to result in the elimination of infection and the protection of the decontaminated tooth from future microbial invasion. During root canal treatment, it is possible that the gutta-percha cones, which are a permanent filling in the treatment, become contaminated. Before being placed in the root canal, it must be sterilized. Additionally, the gutta-percha sterilization process may lead to bacterial growth in the root canal. Thus, gutta-percha sterilization should take place at the same time as root canal cleaning. For this purpose, gutta-percha sterilization must be automated, instead of conventional disinfection methods. The primary objective of this study is to automate the gutta-percha sterilization operation and improve disinfection efficacy with a low turn-around time and high precision. As per the results obtained during the experiment, the turn-around time for sterilization takes 5-8 minutes with good disinfection efficacy in microbial testing and a precision of 92% for 57 cycles of testing. [ABSTRACT FROM AUTHOR]

Iron‐sulfur clusters are well‐established targets in biological nitric oxide (NO) chemistry, but the key intermediate in these processes—a mononitrosylated [Fe4S4] cluster—has not been fully characterized in a protein or a synthetic model thereof. Here, we report the synthesis of a three‐member redox series of isostructural mononitrosylated [Fe4S4] clusters. Mononitrosylation was achieved by binding NO to a 3 : 1 site‐differentiated [Fe4S4]+ cluster; subsequent oxidation and reduction afforded the other members of the series. All three clusters feature a local high‐spin Fe3+ center antiferromagnetically coupled to 3[NO]−. The observation of an anionic NO ligand suggests that NO binding is accompanied by formal electron transfer from the cluster to NO. Preliminary reactivity studies with the monocationic cluster demonstrate that exposure to excess NO degrades the cluster, supporting the intermediacy of mononitrosylated intermediates in NO sensing/signaling. [ABSTRACT FROM AUTHOR]

Here we report an α‐thianthrenium carbonyl species, as the equivalent of an α‐carbonyl carbocation, which is generated by the radical conjugate addition of a trifluoromethyl thianthrenium salt to Michael acceptors. The reactivity allows for the synthesis of Cα‐tetrasubstituted α‐ and β‐amino acid analogues via a Ritter reaction by addition of acetonitrile. Addition of hydroxide, methoxide, and even fluoride can afford α‐heteroatom substituted α‐phenylpropanoates. [ABSTRACT FROM AUTHOR]

The last two decades have witnessed a major revolution in the field of tumor immunology including clinical progress using various immunotherapy strategies. These advances have highlighted the potential for approaches that harness the power of the immune system to fight against cancer. While cancer immunotherapies have shown significant clinical successes, patient responses vary widely due to the complex and heterogeneous nature of tumors and immune responses, calling for reliable biomarkers and therapeutic strategies to maximize the benefits of immunotherapy. Especially, stratifying responding individuals from non-responders during the early stages of treatment could help avoid long-term damage and tailor personalized treatments. In efforts to develop non-invasive means for accurately evaluating and predicting tumor response to immunotherapy, multiple affinity-based agents targeting immune cell markers and checkpoint molecules have been developed and advanced to clinical trials. In addition, researchers have recently turned their attention to substrate and activity-based imaging probes that can provide real-time, functional assessment of immune response to treatment. Here, we highlight some of those recently designed probes that image functional proteases as biomarkers of cancer immunotherapy with a focus on their chemical design and detection modalities and discuss challenges and opportunities for the development of imaging tools utilized in cancer immunotherapy., (© 2023 Wiley-VCH GmbH.)

Armed with the useful properties of small molecules and proteins, peptides hold the potential to be utilized in almost all biomedical research fields. However, the clinical application of peptides has been limited due to their intrinsic drawbacks, such as poor plasma stability and low target binding affinity. The conjugation of peptides to biological, organic (nonbiological), and inorganic materials has recently emerged as a promising strategy to address these problems. Hence, in this article, we provide an overview of the successful outcomes of using peptide‐bio/organic/inorganic conjugates in various biomedical applications, including the diagnosis and treatment of diseases. [ABSTRACT FROM AUTHOR]

The objective of this study was to characterize the tree bark of Araucaria angustifolia, for estimate the energy potential of this biomass as a source of renewable energy and products from biorefineries. Studies have been carried out using thermal analysis (TGA-DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM) and dispersive energy spectroscopy (EDS) for thermochemical and morphological analysis. Through thermal analysis, it is possible to observe in A. angustifolia the thermal effects in the presence of air and nitrogen for a dry sample and its phases in view of the effects of temperature and mass loss. A calorific value measured around 12.23MJ/Kg was also seen, being able to consider this product as an alternative energy source and products such as maltol were identified indicating that substances from biorefineries are present in this biomass. [ABSTRACT FROM AUTHOR]

A new mononuclear cobalt(III)-pentasulfido compound, [(L)Co(S 5 )] (3) has been synthesized by using a convergent redox reaction between elemental sulfur and two new cobalt(II)-thiolato compounds, [(L)Co(SR)] (R=Ph, 2 a; 2,6-Me 2 -C 6 H 4 , 2 b), which in turn were synthesized from a dimeric cobalt(II) complex, [(L) 2 Co 2 ] 2+ (1). Compound 3 features a low-spin, diamagnetic, Co(III) center with a coordinated pentasulfido (S 5 2- ) chain and has no precedence in the literature. Compound 3 is highly stable towards reduction with a potential of -1.36 V (vs. Cp 2 Fe + /Cp 2 Fe) and gives back 1 upon chemical/electrochemical reduction. Reaction of 3 with phosphines yields back 1 and phosphine sulfides, while protonation of the coordinated S 5 2- chain in 3 leads to the formation of 1, elemental sulfur and H 2 S. Finally, transfer of the coordinated S 5 2- chain in 3 to selected organic compounds, such as MeI, PhCH 2 Br and PhCOCl, for the generation of organopolysulfido compounds has been demonstrated., (© 2023 Wiley-VCH GmbH.)

mRNA display is a powerful biological display platform for the directed evolution of proteins and peptides. mRNA display libraries covalently link the displayed peptide or protein (phenotype) with the encoding genetic information (genotype) through the biochemical activity of the small molecule puromycin. Selection for peptide/protein function is followed by amplification of the linked genetic material and generation of a library enriched in functional sequences. Iterative selection cycles are then performed until the desired level of function is achieved, at which time the identity of candidate peptides can be obtained by sequencing the genetic material. The purpose of this review is to discuss the development of mRNA display technology since its inception in 1997 and to comprehensively review its use in the selection of novel peptides and proteins. We begin with an overview of the biochemical mechanism of mRNA display and its variants with a particular focus on its advantages and disadvantages relative to other biological display technologies. We then discuss the importance of scaffold choice in mRNA display selections and review the results of selection experiments with biological (e.g., fibronectin) and linear peptide library architectures. We then explore recent progress in the development of "drug-like" peptides by mRNA display through the post-translational covalent macrocyclization and incorporation of non-proteogenic functionalities. We conclude with an examination of enabling technologies that increase the speed of selection experiments, enhance the information obtained in post-selection sequence analysis, and facilitate high-throughput characterization of lead compounds. We hope to provide the reader with a comprehensive view of current state and future trajectory of mRNA display and its broad utility as a peptide and protein design tool. [ABSTRACT FROM AUTHOR]

We report the synthesis and characterization of the first terminal imido complex of an Fe–S cluster, (IMes)3Fe4S4=NDipp (2; IMes=1,3‐dimesitylimidazol‐2‐ylidene, Dipp=2,6‐diisopropylphenyl), which is generated by oxidative group transfer from DippN3 to the all‐ferrous cluster (IMes)3Fe4S4(PPh3). This two‐electron process is achieved by formal one‐electron oxidation of the imido‐bound Fe site and one‐electron oxidation of two IMes‐bound Fe sites. Structural, spectroscopic, and computational studies establish that the Fe–imido site is best described as a high‐spin Fe3+ center, which is manifested in its long Fe−N(imido) distance of 1.763(2) Å. Cluster 2 abstracts hydrogen atoms from 1,4‐cyclohexadiene to yield the corresponding anilido complex, demonstrating competency for C−H activation. [ABSTRACT FROM AUTHOR]

We have developed a stainless steel internal tendon anchor that is used to strengthen a tendon repair. This study tested its use in vitro to produce a repair that can withstand the tensile strength demands of early active flexion. Fresh human cadaver flexor digitorum profundus tendons were harvested, divided, and then repaired using four different techniques: Kessler, Becker or Savage stitches, or the internal tendon anchor. The internal splint repairs demonstrated a 99–270% increase in mean maximal linear tensile strength and a 49–240% increase in mean ultimate tensile strength over the other repairs. It is hoped that this newly developed internal anchor will provide a repair that will be strong enough to allow immediate active range of motion. [ABSTRACT FROM PUBLISHER]

The discovery of potent STAT3 inhibitors has gained noteworthy impetus in the last decade. In line with this trend, considering the proven biological importance of 1,2,4-triazoles, herein, we are reporting the design, synthesis, pharmacokinetic profiles, and in vitro anticancer activity of novel C3-linked 1,2,4-triazole-N-arylamide hybrids and their in silico proposed mechanism of action via inhibition of STAT3. The 1,2,4-triazole scaffold was selected as a privilege ring system that is embedded in core structures of a variety of anticancer drugs which are either in clinical use or still under clinical trials. The designed 1,2,4-triazole derivatives were synthesized by linking the triazole-thione moiety through amide hydrophilic linkers with diverse lipophilic fragments. In silico study to predict cytotoxicity of the new hybrids against different kinds of human cancer cell lines as well as the non-tumor cells was conducted. The multidrug-resistant human breast adenocarcinoma cells (MDA-MB-231) was found most susceptible to the cytotoxic effect of synthesized compounds and hence were selected to evaluate the in vitro anticancer activity. Four of the designed derivatives showed promising cytotoxicity effects against selected cancer cells, among which compound 12 showed the highest potency (IC50 = 3.61 µM), followed by 21 which displayed IC50 value of 3.93 µM. Also, compounds 14 and 23 revealed equipotent activity with the reference cytotoxic agent doxorubicin. To reinforce these observations, the obtained data of in vitro cytotoxicity have been validated in terms of ligand–protein interaction and new compounds were analyzed for ADMET properties to evaluate their potential to build up as good drug candidates. This study led us to identify two novel C3-linked 1,2,4-triazole-N-arylamide hybrids of interesting antiproliferative potentials as probable lead inhibitors of STAT3 with promising pharmacokinetic profiles. [ABSTRACT FROM AUTHOR]

By employing the computational protocol for calculation of reduction potentials of the Fe4S4‐containing species validated using a representative series of well‐defined synthetic complexes, we focused on redox properties of two prototypical radical SAM enzymes to reveal how they transform SAM into the reactive 5'‐deoxyadenosyl radical, and how they tune this radical for its proper biological function. We found the reduction potential of SAM is indeed elevated by 0.3–0.4 V upon coordination to Fe4S4, which was previously speculated in the literature. This makes a generation of 5'‐deoxyadenosyl radical from SAM less endergonic (by ca. 7–9 kcal mol−1) and hence more feasible in both enzymes as compared to the identical process in water. Furthermore, our calculations indicate that the enzyme‐bound 5'‐deoxyadenosyl radical has a significantly lower reduction potential than in referential aqueous solution, which may help the enzymes to suppress potential side redox reactions and simultaneously elevate its proton‐philic character, which may, in turn, promote the radical hydrogen‐atom abstraction ability. [ABSTRACT FROM AUTHOR]

Friction stir welding (FSW) is a solid state technique used to join aluminum alloys effectively compared with other conventional welding methods. AA6061/AA2014 Al-alloys in dissimilar combination were processed for welding because they have significant demand in various engineering applications. The process parameters chosen for welding are tool rotational speed (710 to 1120 rpm), weld speed (20 to 40 mm/min) and pin profile (Triangular, Square and Pentagon) were arranged in L9 orthogonal array. The weld joint properties such as hardness and tensile strength were tested as per ASTM standard. The microstructure of weld profile was studied with optical, scanning electron microscopy. The welds processed at 900-20-S were exhibits higher properties such as UTS, YS and hardness as 191, 170 MPa, 110 HV respectively. [ABSTRACT FROM AUTHOR]

Laser beam welding is an essential metal joining method for magnesium and its alloys with their growing applications in automotive, aerospace, marine, etc. In this research paper, the experimental modelling for laser beam welding of ZE41 Mg alloy and the mechanical and metallurgical characterisation after welding are reported. The effects of weld scan speed and laser beam power on the weld geometry for bead on plates of ZE41 Mg alloy using a continuous-wave CO2 laser system were analysed in this work. The microstructure, hardness, and radiography analysis were discussed. The results indicate the influence of laser parameters and the validity of the regression equations developed for the optimisation of process parameters. [ABSTRACT FROM AUTHOR]

IspH/LytB, an oxygen‐sensitive [4Fe‐4S] enzyme, catalyzes the last step of the methylerythritol phosphate (MEP) pathway, a target for the development of new antimicrobial agents. This metalloenzyme converts (E)‐4‐hydroxy‐3‐methylbut‐2‐en‐1‐yl diphosphate (HMBPP) into the two isoprenoid precursors: isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP). Here, the synthesis of (S)‐[4‐2H1]HMBPP and (R)‐[4‐2H1]HMBPP is reported together with a detailed NMR analysis of the products formed after their respective incubation with E. coli IspH/LytB in the presence of the biological reduction system used by E. coli to reduce the [4Fe‐4S] center. (S)‐[4‐2H1]HMBPP was converted into [4‐2H1]DMAPP and (E)‐[4‐2H1]IPP, whereas (R)‐[4‐2H1]HMBPP yielded [4‐2H1]DMAPP and (Z)‐[4‐2H1]IPP, hence providing the direct enzymatic evidence that the mechanism catalyzed by IspH/LytB involves a rotation of the CH2OH group of the substrate to display it away from the [4Fe‐4S]. [ABSTRACT FROM AUTHOR]

Incorporation of monatomic 2p ligands into the core of iron–sulfur clusters has been researched since the discovery of interstitial carbide in the FeMo cofactor of Mo‐dependent nitrogenase, but has proven to be a synthetic challenge. Herein, two distinct synthetic pathways are rationalized to install nitride ligands into targeted positions of W‐Fe‐S clusters, generating unprecedented nitride‐ligated iron–sulfur clusters, namely [(Tp*)2W2Fe6(μ4‐N)2S6L4]2− (Tp*=tris(3,5‐dimethyl‐1‐pyrazolyl)hydroborate(1−), L=Cl− or Br−). 57Fe Mössbauer study discloses metal oxidation states of WIV2FeII4FeIII2 with localized electron distribution, which is analogous to the mid‐valent iron centres of FeMo cofactor at resting state. Good agreement of Mössbauer data with the empirical linear relationship for Fe–S clusters indicates similar ligand behaviour of nitride and sulfide in such clusters, providing useful reference for reduced nitrogen in a nitrogenase‐like environment. [ABSTRACT FROM AUTHOR]

Herein, a PD-L1 targeted native peptide was developed for PET imaging. 18F and 64Cu were utilized to label the peptide. To improve the pharmacokinetics and biodistribution of the tracers, the peptide was further pegylated to form star-like tetramers. Consequently, four tracers were synthesized with acceptable radiochemical characteristics and their in vivo pharmacokinetics and PD-L1 imaging capability were systematically evaluated. This proof-of-principle study may provide new possibilities for PD-L1 PET imaging in cancers. [ABSTRACT FROM AUTHOR]

Biaryl atropisomers are of great importance in natural products, pharmaceuticals, and asymmteric synthesis. The efficient synthesis of these chiral scaffolds with full enantiocontrol and high diversity remains challenging. Reported herein is a Pd‐catalyzed atroposelective C−H allylation with tert‐leucine as an efficient catalytic chiral transient auxiliary. A wide range of enantioenriched biaryl aldehydes were prepared in synthetically useful yields with excellent enantioselectivity (up to >99 % ee) through β‐O elimination. The reaction could be carried out on a gram scale without erosion of the ee value. A variety of axially chiral carboxylic acids could be obtained with high enantiopurity. The resulting axially chiral biaryl aldehydes and carboxylic acids might be used in asymmetric synthesis as chiral ligands and/or organocatalysts. A Pd‐catalyzed atroposelective C−H allylation with allylic surrogates is reported. tert‐Leucine was identified as an efficient catalytic transient chiral auxiliary. A range of enantioenriched biaryls were prepared in synthetically useful yields with enantioselectivities up to >99 % ee through β‐O elimination. The reaction could be scaled up and the products could be further converted into enantiomerically pure axially chiral carboxylic acids. [ABSTRACT FROM AUTHOR]

[Fe4S4] iron–sulfur clusters are typically anchored to the protein scaffold via four cysteine residues, but in a number of proteins one of the Cys is replaced with another ligand. The biological role of such a replacement is unknown although essential to maintain catalytic activity. Here, we explore the geometries and electronic structures of 3:1 site differentiated model compounds [Fe4S4][S(CH3)]3(L) using quantum chemical methods. The unique ligands L were chosen to represent biologically relevant molecules: methanethiol (represents cysteine), acetic acid (asparagine), 4‐methylimidazole (histidine), and water/hydroxyl anion. Each ligand was considered as deprotonated anion or protonated neutral molecule. We found the replacements do not influence structure of the cluster significantly. On the contrary, the impact on the reduction potentials is visible and may reach up to 0.2 V depending on the charge of the ligand. We also studied previously unconsidered asymmetry in excess charge distribution in a reduced [Fe4S4]+ cubane caused by a unique ligation. Our findings show that protonation/deprotonation reactions may provide gating mechanisms in the electron flow carried by iron–sulfur clusters. Additionally, we calculated X‐ray absorption (XAS) and emission (XES) spectra of all compounds under investigation. Particularly, theoretical XES show clear features characteristic to each unique ligand. However, their intensity may be too small to be observed experimentally. [ABSTRACT FROM AUTHOR]

Sulfur-bridged binuclear structures [2M-2S] play a pivotal role in a variety of chemical processes such as bond breaking and formation and electron transfer. In general, structural persistence is deemed essential to the respective function but owing to the lack of a suitable molecular model system, the current understanding of the factors that control the thermodynamic and kinetic stability of [2M-2S] cores clearly is limited. This work reports a series of binuclear complexes of nickel derived from a 1,4-terphenyldithiophenol ligand platform that is ideally suited for mechanistic work to overcome this limitation. Redox-induced assembly and disassembly of S-bridged [2M-2S] fragments have been investigated at the molecular level. As part of an extended square scheme, metastable binuclear structures that are significant mechanistically have been identified, characterized, and their reactivity studied quantitatively. Electronic properties that are inherent to [2M-2S] structures and determine thermodynamic and kinetic stability are differentiated from steric effects imposed by co-ligands. [ABSTRACT FROM AUTHOR]

A highly active FeSe2 electrocatalyst for durable overall water splitting was prepared from a molecular 2Fe-2Se precursor. The as-synthesized FeSe2 was electrophoretically deposited on nickel foam and applied to the oxygen and hydrogen evolution reactions (OER and HER, respectively) in alkaline media. When used as an oxygen-evolution electrode, a low 245 mV overpotential was achieved at a current density of 10 mA cm−2, representing outstanding catalytic activity and stability because of Fe(OH)2/FeOOH active sites formed at the surface of FeSe2. Remarkably, the system is also favorable for the HER. Moreover, an overall water-splitting setup was fabricated using a two-electrode cell, which displayed a low cell voltage and high stability. In summary, the first iron selenide material is reported that can be used as a bifunctional electrocatalyst for the OER and HER, as well as overall water splitting. [ABSTRACT FROM AUTHOR]

In the present paper, highly transparent, monolithic and hydrophobic silica aerogel monoliths were prepared by using tetraethoxysilane (TEOS) as precursor and methyltriethoxysilane (MTES) as co-precursor with different MTES/TEOS molar ratios (M) by two-step acid-base catalyzed sol-gel process followed by supercritical alcohol drying. The molar ratio of TEOS, ethanol (EtOH), water (0.001 M oxalic acid catalyst) and ammonium hydroxide (1 M NHOH) was kept constant at 1:5:3.5:3.5 respectively, while the molar ratio of MTES/TEOS (M) was varied from 0 to 0.75. It has been observed that as the M value increases, the gelation time increases. It has been found that lower (0.25) M values resulted in highly transparent (optical transmission >90 % for a 10 mm thick sample at 700 nm wavelength) and negligible volume shrinkage (<10 %) but less hydrophobic aerogels, whereas higher (0.75) M values resulted in semitransparent (<25 % optical transmission at 700 nm for a 10 mm thick sample) aerogels with >10 % volume shrinkage but excellent hydrophobicity. A good compromise of acceptable optical transmittance (~87 % optical transmission at 700 nm wavelength for a 10 mm thick sample) with negligible volume shrinkage (6 %) were obtained at M = 0.50. The hydrophobicity of the aerogels was tested by measuring the contact angle between a water droplet and silica aerogel surface. The hydrophobicity was confirmed by Fourier transform infra-red spectroscopy and contact angle measurements. the aerogels have been characterized by percentage of volume shrinkage, optical transmittance, scanning electron microscopy, thermal conductivity measurements and thermogravimetric analysis and differential thermal analysis. [ABSTRACT FROM AUTHOR]

Phenotype-based screening of diverse compound collections generated by privileged substructure-based diversity-oriented synthesis (pDOS) is considered one of the prominent approaches in the discovery of novel drug leads. However, one key challenge that remains is the development of efficient and modular synthetic routes toward the facile access of privileged small-molecule libraries with skeletal and stereochemical complexity and drug-like properties. In this regard, a novel and diverse one-pot procedure for the diastereoselective synthesis of privileged polycyclic benzopyrans and benzoxepines is described herein. These unexplored chemotypes were accessed by utilizing an acid-mediated diaza-Diels-Alder reaction of 2-allyloxy- and/or homoallyloxy benzaldehyde with 2-aminoazine building blocks. Profiling of representative analogues against blood-stage Plasmodium falciparum parasites identified three lead candidates with low micromolar antimalarial activity. [ABSTRACT FROM AUTHOR]

A palladium-catalyzed asymmetric allyl-allyl cross-coupling of acetates of racemic Morita-Baylis-Hillman adducts and allylB(pin) has been developed using a spiroketal-based bis(phosphine) as the chiral ligand, thus affording a series of chiral 1,5-dienes bearing a vinylic ester functionality in good yields, high branched regioselectivities, and uniformly excellent enantioselectivities (95-99 % ee). Further synthetic manipulations of the allylation products provided novel ways for rapid access to a range of chiral polycyclic lactones and polycyclic lactams, as well as the antidepressant drug (−)-Paroxetine, in high optical purities. [ABSTRACT FROM AUTHOR]