bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ammonia Formation Catalyzed by a Dinitrogen‐Bridged Dirhenium Complex Bearing PNP‐Pincer Ligands under Mild Reaction Conditions**
Authors: Meng Fanqiang , Kuriyama Shogo , Tanaka Hiromasa , Egi Akihito , Yoshizawa Kazunari , Nishibayashi Yoshiaki 
Published: April 2021

AbstractA series of rhenium complexes bearing a pyridine‐based PNP‐type pincer ligand are synthesized from rhenium phosphine complexes as precursors. A dinitrogen‐bridged dirhenium complex bearing the PNP‐type pincer ligands catalytically converts dinitrogen into ammonia during the reaction with KC8as a reductant and [HPCy3]BArF4(Cy=cyclohexyl, ArF=3,5‐(CF3)2C6H3) as a proton source at −78 °C to afford 8.4 equiv of ammonia based on the rhenium atom of the catalyst. The rhenium‐dinitrogen complex also catalyzes silylation of dinitrogen in the reaction with KC8as a reductant and Me3SiCl as a silylating reagent under ambient reaction conditions to afford 11.7 equiv of tris(trimethylsilyl)amine based on the rhenium atom of the catalyst. These results demonstrate the first successful example of catalytic nitrogen fixation under mild reaction conditions using rhenium‐dinitrogen complexes as catalysts.
Isolierung neutraler, mono‐ und dikationischer B2P2‐Ringe durch Addition eines Diphosphans an eine Bor‐Bor‐Dreifachbindung
Authors: Brückner Tobias , Fantuzzi Felipe , Stennett Tom E. , Krummenacher Ivo , Dewhurst Rian D. , Engels Bernd , Braunschweig Holger 
Published: April 2021

AbstractDas NHC‐stabilisierte Diborin B2(SIDep)2 (SIDep=1,3‐Bis(2,6‐diethylphenyl)imidazolin‐2‐yliden) unterzieht sich bei Raumtemperatur einer P‐P‐Bindungsaktivierung mit Tetraethyldiphosphan, wobei mittels 1,2‐Diphosphinierung über ein Diphosphoryldiboren in hohen Ausbeuten B2P2‐Heterocyclen gebildet werden. In Abhängigkeit vom verwendeten Oxidationsmittel und Gegenion kann dieser Heterocyclus zu einem Radikalkation beziehungsweise Dikation oxidiert werden. Beginnend mit dem planaren, neutralen 1,3‐Bis(alkyliden)‐1,3‐diborata‐2,4‐diphosphoniocyclobutan führt jeder Oxidationsschritt zu einer verminderten B‐B‐Bindungslänge und dem Verlust der Planarität durch die Kationisierung. Röntgenstrukturanalysen in Kombination mit DFT‐ und CASSCF/NEVPT2‐Rechnungen offenbaren für die NHC‐stabilisierten dikationischen B2P2‐Ringe geschlossenschalige, schmetterlingsartige Strukturen, wovon die diradikaloiden Isomere mit planarem Ring in energetischer Nähe liegen.
Genetic Encoding and Enzymatic Deprotection of a Latent Thiol Side Chain to Enable New Protein Bioconjugation Applications
Authors: Reille‐Seroussi Marie , Meyer‐Ahrens Pascal , Aust Annika , Feldberg Anna‐Lena , Mootz Henning D. 
Published: April 2021

AbstractThe thiol group of the cysteine side chain is arguably the most versatile chemical handle in proteins. To expand the scope of established and commercially available thiol bioconjugation reagents, we genetically encoded a second such functional moiety in form of a latent thiol group that can be unmasked under mild physiological conditions. Phenylacetamidomethyl (Phacm) protected homocysteine (HcP) was incorporated and its latent thiol group unmasked on purified proteins using penicillin G acylase (PGA). The enzymatic deprotection depends on steric accessibility, but can occur efficiently within minutes on exposed positions in flexible sequences. The freshly liberated thiol group does not require treatment with reducing agents. We demonstrate the potential of this approach for protein modification with conceptually new schemes for regioselective dual labeling, thiol bioconjugation in presence of a preserved disulfide bond and formation of a novel intramolecular thioether crosslink.
Spatial Confinement Tunes Cleavage and Re‐Formation of C=N Bonds in Fluorescent Molecules
Authors: Liu Keyan , Qiao Xuezhi , Huang Chuanhui , Li Xiao , Xue Zhenjie , Wang Tie 
Published: April 2021

AbstractMolecules in confined spaces exhibit unusual behaviors that are not typically observed in bulk systems. Such behavior can provide alternative strategies for exploring new reaction pathways. Cleavage of the C=N bond of Nile red (NR) in solution is an irreversible reaction. Here, we used spatial confinement within a cationic micelle‐confined system to convert this reaction to a reversible process. The fluorescence of NR shifted between red and green for nine cycles. The new chemical pathway based on spatial confinement can be attributed to two factors: increasing the local concentration of reactants and reducing the reaction energy barrier. This effect is supported by both experimental evidence and theoretical calculations. The cross‐linked silica shell comprising the confinement chamber stabilizes the enclosed molecules. This reduces fluorophore leakage and maintains fluorescence intensity in most environments, including in solution, on paper, and in hydrogel films, and expands practical applications in encrypted information and multi‐informational displays.
Enantio‐ und diastereoselektive, vollständige Hydrierung von Benzofuranen mittels Kaskadenkatalyse
Authors: Moock Daniel , Wagener Tobias , Hu Tianjiao , Gallagher Timothy , Glorius Frank 
Published: April 2021

AbstractWir berichten über eine enantio‐ und diastereoselektive, vollständige Hydrierung von mehrfach substituierten Benzofuranen in einer Eintopf‐Kaskadenkatalyse. Das entwickelte Protokoll ermöglicht den kontrollierten Aufbau von bis zu sechs definierten Stereozentren und erzeugt architektonisch komplexe Octahydrobenzofurane, die in vielen bioaktiven Molekülen vorkommen. Ein einzigartiges Zusammenspiel eines chiralen Ruthenium‐N‐heterozyklischen Carbenkomplexes und eines aus einem Komplexvorläufer in situ aktivierten Rhodiumkatalysators ermöglicht den vorgestellten Prozess.
Macrocyclic FKBP51 Ligands Define a Transient Binding Mode with Enhanced Selectivity
Authors: Voll Andreas M. , Meyners Christian , Taubert Martha C. , Bajaj Thomas , Heymann Tim , Merz Stephanie , Charalampidou Anna , Kolos Jürgen , Purder Patrick L. , Geiger Thomas M. , Wessig Pablo , Gassen Nils C. , Bracher Andreas , Hausch Felix 
Published: April 2021

AbstractSubtype selectivity represents a challenge in many drug discovery campaigns. A typical example is the FK506 binding protein 51 (FKBP51), which has emerged as an attractive drug target. The most advanced FKBP51 ligands of the SAFit class are highly selective vs. FKBP52 but poorly discriminate against the homologs and off‐targets FKBP12 and FKBP12.6. During a macrocyclization pilot study, we observed that many of these macrocyclic analogs have unanticipated and unprecedented preference for FKBP51 over FKBP12 and FKBP12.6. Structural studies revealed that these macrocycles bind with a new binding mode featuring a transient conformation, which is disfavored for the small FKBPs. Using a conformation‐sensitive assay we show that this binding mode occurs in solution and is characteristic for this new class of compounds. The discovered macrocycles are non‐immunosuppressive, engage FKBP51 in cells, and block the cellular effect of FKBP51 on IKKα. Our findings provide a new chemical scaffold for improved FKBP51 ligands and the structural basis for enhanced selectivity.
Isolation of Neutral, Mono‐, and Dicationic B2P2 Rings by Diphosphorus Addition to a Boron−Boron Triple Bond
Authors: Brückner Tobias , Fantuzzi Felipe , Stennett Tom E. , Krummenacher Ivo , Dewhurst Rian D. , Engels Bernd , Braunschweig Holger 
Published: April 2021

AbstractThe NHC‐stabilised diboryne (B2(SIDep)2; SIDep=1,3‐bis(2,6‐diethylphenyl)imidazolin‐2‐ylidene) undergoes a high‐yielding P−P bond activation with tetraethyldiphosphine at room temperature to form a B2P2 heterocycle via a diphosphoryldiborene by 1,2‐diphosphination. The heterocycle can be oxidised to a radical cation and a dication, respectively, depending on the oxidant used and its counterion. Starting from the planar, neutral 1,3‐bis(alkylidene)‐1,3‐diborata‐2,4‐diphosphoniocyclobutane, each oxidation step leads to decreased B−B distances and loss of planarity by cationisation. X‐ray analyses in conjunction with DFT and CASSCF/NEVPT2 calculations reveal closed‐shell singlet, butterfly‐shaped structures for the NHC‐stabilised dicationic B2P2 rings, with their diradicaloid, planar‐ring isomers lying close in energy.
Electro‐Conductive Single‐Molecule Magnet Composed of a Dysprosium(III)‐Phthalocyaninato Double‐Decker Complex with Magnetoresistance
Authors: Sato Tetsu , Breedlove Brian K. , Yamashita Masahiro , Katoh Keiichi 
Published: April 2021

AbstractA one‐dimensional (1D) arrangement of an unsubstituted partially oxidized Dy3+ double‐decker complex, [DyPc2]Ix (Pc=phthalocyaninato, I=iodide; 1.93<x<2.26) (1), was obtained by using electro‐oxidation and chemical oxidation. In 1, the Pc ligands were partially oxidized, and I3− ion was present as a counter ion. From the results of spectrophotometric analysis on 1, the π radicals were delocalized in a 1D column and behaved as a conductor even at low‐temperatures. Since conductivity was observed at temperatures lower than the blocking temperature (TB), magnetoresistance (MR) effects corresponding to a magnetic hysteresis of single‐molecule magnet (SMM) were observed when the galvanomagnetic characteristics were investigated at 2.2 K.
A Light‐Operated Molecular Cable Car for Gated Ion Transport
Authors: Wang Chenxi , Wang Shunkang , Yang Huiting , Xiang Yanxin , Wang Xuebin , Bao Chunyan , Zhu Linyong , Tian He , Qu Da‐Hui 
Published: April 2021

AbstractInspired by the nontrivial and controlled movements of molecular machines, we report an azobenzene‐based molecular shuttle PR2, which can perform light‐gated ion transport across lipid membranes. The amphiphilicity and membrane‐spanning molecular length enable PR2 to insert into the bilayer membrane and efficiently transport K+ (EC50=4.1 μm) through the thermally driven stochastic shuttle motion of the crown ether ring along the axle. The significant difference in shuttling rate between trans‐PR2 and cis‐PR2 induced by molecular isomerization enables a light‐gated ion transport, i.e., ON/OFF in situ regulation of transport activity and single‐channel current. This work represents an example of using a photoswitchable molecular machine to realize gated ion transport, which demonstrates the value of molecular machines functioning in biomembranes.
Adducts of the Parent Boraphosphaketene H2BPCO and their Decarbonylative Insertion Chemistry
Authors: Hagspiel Stephan , Fantuzzi Felipe , Dewhurst Rian D. , Gärtner Annalena , Lindl Felix , Lamprecht Anna , Braunschweig Holger 
Published: April 2021

AbstractThe first examples of Lewis base adducts of the parent boraphosphaketene (H2B‐PCO) and their cyclodimers are prepared. One of these adducts is shown to undergo mild decarbonylation and phosphinidene insertion into a B−C bond of a borole, forming very rare examples of 1,2‐phosphaborinines, B/P isosteres of benzene. The strong donor properties of these 1,2‐phosphaborinines are confirmed by the synthesis of their π complexes with the Group 6 metals.
Chiral Metal Nanoparticle Superlattices Enabled by Porphyrin‐Based Supramolecular Structures
Authors: Yang Fei , Liu Xinyong , Yang Zhijie 
Published: April 2021

AbstractHerein, we show that chiral metal nanoparticle superlattices can be produced through coassembly of achiral metal nanoparticles and porphyrin‐based organic molecules. This chirality transfer from molecules to nanoparticle superstructures across three orders of magnitude in length scale is enabled by the hetero chain‐chain van der Waals interactions. As far as we know, these are the first chiral nanoparticle assemblies based on chirality transfer through weak van der Waals forces. The dimensionality of the nanoparticle superlattices (1D chiral chains, 2D chiral sheets (cones), and 3D chiral particles) can be controlled based on a same synthetic chiral porphyrin molecule. Metalation of these porphyrin molecules with zinc cations results in the switching of molecular packing from J‐type to H‐type, which thereby produces 1D chiral nanoparticle chains. Functionalization of these zinc porphyrins with oleylamine can induce the assembly of nanoparticles into 2D chiral nanoparticle sheets.
Atomic Sulfur Filling Oxygen Vacancies Optimizes H Absorption and Boosts the Hydrogen Evolution Reaction in Alkaline Media
Authors: Jin Jing , Yin Jie , Liu Hongbo , Huang Bolong , Hu Yang , Zhang Hong , Sun Mingzi , Peng Yong , Xi Pinxian , Yan Chun‐Hua 
Published: April 2021

AbstractThe hydrogen evolution reaction (HER) usually has sluggish kinetics in alkaline solution due to the difficulty in forming binding protons. Herein we report an electrocatalyst in which sulfur atoms are doping in the oxygen vacancies (VO) of inverse spinel NiFe2O4 (S‐NiFe2O4) to create active sites with enhanced electron transfer capability. This electrocatalyst has an ultralow overpotential of 61 mV at the current density of 10 mA cm−2 and long‐term stability of 60 h at 1.0 Acm−2 in 1.0 M KOH media. In situ Raman spectroscopy revealed that S sites adsorb hydrogen adatom (H*) and in situ form S‐H*, which favor the production of hydrogen and boosts HER in alkaline solution. DFT calculations further verified that S introduction lowered the energy barrier of H2O dissociation. Both experimental and theoretical investigations confirmed S atoms are active sites of the S‐NiFe2O4.
Synthesis of Ionic Vinylene‐Linked Covalent Organic Frameworks through Quaternization‐Activated Knoevenagel Condensation
Authors: Meng Fancheng , Bi Shuai , Sun Zuobang , Jiang Biao , Wu Dongqing , Chen Jie‐Sheng , Zhang Fan 
Published: April 2021

AbstractWe developed a simple approach to synthesizing ionic vinylene‐linked two‐dimensional covalent organic frameworks (COFs) through a quaternization‐promoted Knoevenagel condensation at three aromatic methyl carbon atoms ofN‐ethyl‐2,4,6‐trimethylpyridinium halide with multitopic aromatic aldehyde derivatives. The resultant COFs exhibited a honeycomb‐like structure with high crystallinity and surface areas as large as 1343 m2 g−1. The regular shape‐persistent nanochannels and the positively charged polymeric frameworks allowed the COFs to be uniformly composited with linear polyethylene oxide and lithium salt, displaying ionic conductivity as high as 2.72×10−3 S cm−1.
Reconstructing tooth crown heights and enamel caps: A comparative test of three existing methods with recommendations for their use
Authors: O'Hara Mackie C. , Guatelli‐Steinberg Debbie 
Published: April 2021

AbstractStudies of enamel growth and thickness, whether in paleoanthropology, bioarchaeology, or primatology, require measurements of crown height (CH), cuspal enamel thickness (CET), average (AET), and/or regional enamel thickness (RegAET) on complete, unworn crowns. Yet because fully unworn crowns are uncommon, three methods to bolster sample sizes by reconstructing slightly worn teeth have been developed: Profile, Polynomial, and Pen Tool. Although these methods have been tested for accuracy, no study has yet directly compared the three methods to assess their performance across CH, CET, AET, and RegAET measurements. Moreover, it is currently unclear how accurate the methods are when reconstructing crowns with varying degrees of wear. The present study addresses this gap in our understanding of how these methods perform on four key dental measurements, evaluates the degree of wear for which accurate crown reconstructions can be completed, and offers recommendations for applying these methods. Here, the methods are compared on Paranthropus robustus mandibular molars, a sample chosen because it exhibits variable morphology, presenting a challenge for reconstruction methods. For minimally worn teeth, Profile, Polynomial, and Pen Tool methods can be employed (in that order) for all measurements except CET, which cannot be reliably measured on reconstructions. For teeth with wear that obliterates the nadir of the occlusal basin or dentin horns, CH and AET can be measured using Profile and Polynomial reconstructions; however, no other measurements or methods were reliable. Recommendations provided here will make it possible to increase sample sizes and replicability, enhancing studies of enamel thickness and growth.
Effect of Atorvastatin on Knee Cartilage Volume in Patients With Symptomatic Knee Osteoarthritis: Results From a Randomized Placebo‐Controlled Trial
Authors: Wang Yuanyuan , Jones Graeme , Hill Catherine , Wluka Anita E. , Forbes Andrew B. , Tonkin Andrew , Hussain Sultana Monira , Ding Changhai , Cicuttini Flavia M. 
Published: April 2021

ObjectiveTo determine whether atorvastatin slows tibial cartilage volume loss in patients with symptomatic knee osteoarthritis (OA) in a multicenter, randomized, double‐blind, placebo‐controlled trial.MethodsParticipants ages 40–70 years were randomized to receive oral atorvastatin (40 mg once daily) (n = 151) or matching placebo (n = 153). The primary end point was annual percentage change in tibial cartilage volume over 2 years, assessed using magnetic resonance imaging (MRI). The prespecified secondary end points were progression of cartilage defects and bone marrow lesions over 2 years, which were assessed using MRI and change in Western Ontario and McMaster Universities Osteoarthritis (WOMAC) Index pain, stiffness, and function scores.ResultsA total of 248 of 304 participants (81.6%) completed the trial (mean age 55.7 years; 55.6% women). The annual change in tibial cartilage volume differed minimally between the atorvastatin and placebo groups (mean change –1.66% versus –2.17%, between‐group difference 0.50% [95% confidence interval (95% CI) –0.17%, 1.17%]). There were no significant differences in the progression of cartilage defects (odds ratio [OR] 0.86 [95% CI 0.52, 1.41]) or progression of bone marrow lesions (OR 1.00 [95% CI 0.62, 1.63]). Moreover, there were no significant differences in change in WOMAC pain, stiffness, or function scores over 2 years between the atorvastatin and placebo groups (mean change in pain score –36.0 versus –29.5, adjusted difference –2.7 [95% CI –27.1, 21.7]; mean change in stiffness score –14.2 versus –11.8, adjusted difference –0.2 [95% CI –12.2, 11.8]; mean change in function score –89.4 versus –87.5, adjusted difference 0.3 [95% CI –83.1, 83.6]). The incidence of adverse events (AEs) was similar between the atorvastatin and placebo groups (57 [37.7%] versus 52 [34.0%] experiencing AEs).ConclusionTreatment with oral atorvastatin (40 mg once daily), compared to placebo, did not significantly reduce cartilage volume loss over 2 years in patients with symptomatic knee OA. These findings do not support the use of atorvastatin for the treatment of knee OA.
Sodium‐Ion Capacitors: Recent Development in Electrode Materials
Authors: Zhang Zhihao , Gu Zhihao , Zhang Chenguang , Li Jiabao , Wang Chengyin 
Published: April 2021

AbstractSodium‐ion hybrid capacitors (SICs), combining the advantages of both sodium‐ion batteries (SIBs) and electrochemical supercapacitors, have captured sustained attention in the field of energy storage devices due to their high energy and power density, long lifespan, and excellent operation stability. However, conventional SICs based on battery‐type anodes and capacitive‐type cathodes suffer from imbalance on capacity and kinetics. In this regard, rational structure design on electrode materials is still necessary for SICs. Over the past two decades, tremendous efforts have been devoted to the exploration of suitable electrode materials to fabricate high‐performance SICs. Herein, after a brief introduction on the charge storage mechanisms of SICs, the recent developments on electrode materials for SICs are summarized, especially focusing on material design strategies as well as the relationship between structure and corresponding electrochemical performances. Furthermore, the challenges and opportunities for the further development of SICs are also proposed.
Sustainable development in the Legal Amazon: energy recovery from açaí seeds
Authors: Maciel‐Silva Francisco W , Buller Luz S , M B B Gonçalves Maria L , Rostagno Mauricio A , Forster‐Carneiro Tânia 
Published: April 2021

AbstractThe Brazilian açaí industry reached national and international prominence in the last few years. Its final product, mainly frozen pulp, became popular worldwide, accounting for a high market share, including exports. Nevertheless, the solid by‐products arising from the processing are not always discarded in an environmentally suitable manner. This review presents a scientometric analysis of açaí research in the last 27 years (1993 to 2019), applying a longitudinal bibliometric study. Through data analysis, it can be observed that Brazil and the USA are the countries that mostly contributed to the development of açaí research. Although Brazil has more publications, the USA presents more articles in partnership with 21 countries. The results also showed that few documents addressed renewable energy recovery with the following technologies: combustion, pyrolysis, supercritical water hydrolysis, and anaerobic digestion. Further analysis of the anaerobic digestion of the totality of açaí seeds generated in Brazil indicated that, theoretically, the electric energy from biogas burning could supply the whole frozen pulp industry requirement with an additional surplus for sales to the grid. Hence, electricity replacement contributes to greenhouse gas mitigation. The assessment of the potential electric energy generation illustrates how technological integration can be an innovative way to rethink the açaí production chain using a circular economy concept. Moreover, the technological advances could stimulate sustainable agro‐industrial intensification in areas such as the Legal Amazon, considered a hotspot for climate change mitigation. © 2021 Society of Industrial Chemistry and John Wiley & Sons Ltd.
Self‐emulsifying drug delivery system of (R)‐α‐lipoic acid to improve its stability and oral absorption
Authors: Banik Sujan , Halder Shimul , Sato Hideyuki , Onoue Satomi 
Published: April 2021

AbstractThe present study was designed to develop a self‐emulsifying drug delivery system (SEDDS) of (R)‐α‐lipoic acid (RLA) to improve the physicochemical and nutraceutical properties of RLA. RLA/SEDDS was prepared using medium‐chain triglycerides, Tween 80, and polyethylene glycol 400 as oil, surfactant, and co‐surfactant, respectively. The preferable composition of SEDDS was selected according to a pseudo‐ternary phase diagram for improved emulsification properties, and its physicochemical and pharmacokinetic properties were evaluated. RLA/SEDDS showed the immediate formation of fine micelles with a mean droplet size of approximately 260 nm when introduced into aqueous media. In simulated gastric fluid, this system could significantly improve the dissolution behavior of RLA and prevent the degradation of RLA, possibly due to the encapsulation of RLA into the emulsion structure. Following the oral administration of RLA/SEDDS (10 mg RLA/kg) in rats, systemic exposure to RLA and dihydrolipoic acid (DHLA), a reduced form of RLA, increased by 7‐ and 3‐fold, respectively. The improved dissolution and gastric stability of RLA could contribute to enhancing systemic exposure to RLA and DHLA after oral administration. From these findings, RLA/SEDDS might be an efficacious dosage option for improving the oral bioavailability as well as nutraceutical properties of RLA.