bluuebunny/crossref_metadata_2025_split huggingface dataset:
Silylierte Schwefelsäure: Herstellung eines Tris(trimethylsilyl)oxosulfonium[(Me3Si‐O)3SO]+‐Salzes
Authors: Bläsing Kevin , Labbow Rene , Schulz Axel , Villinger Alexander 
Published: April 2021

AbstractDie Chemie der silylierten Schwefelsäure, O2S(OSiMe3)2 (T2SO4, T=Me3Si; auch bekannt als Bis(trimethylsilyl)sulfat), wurde im Detail untersucht, mit dem Ziel, die formalen Autosilylierungsprodukte der silylierten Schwefelsäure, [T3SO4]+ und [TSO4]−, in Analogie zu den bekannten protonierten Spezies, [H3SO4]+ und [HSO4]−, zu synthetisieren. Die Synthese des [TSO4]−‐Ions gelingt nur, wenn eine Base, wie z. B. OPMe3, die bei der Silylierung ein schwach koordinierendes Kation bildet, mit T2SO4 umgesetzt wird, was zur Bildung von [Me3POT]+[TSO4]− führt. Die [T3SO4]+‐Salze können ausgehend von T2SO4 in der Reaktion mit [T‐H‐T]+[B(C6F5)4]− oder T+[CHB11Br6H5]− isoliert werden, aber nur, wenn ein schwach koordinierendes Anion als Gegenion verwendet wird. Alle silylierten Verbindungen konnten kristallisiert und strukturell charakterisiert werden.
Anisotropic Synthetic Allomelanin Materials via Solid‐State Polymerization of Self‐Assembled 1,8‐Dihydroxynaphthalene Dimers
Authors: Zhou Xuhao , Gong Xinyi , Cao Wei , Forman Christopher J. , Oktawiec Julia , D'Alba Liliana , Sun Hao , Thompson Matthew P. , Hu Ziying , Kapoor Utkarsh , McCallum Naneki C. , Malliakas Christos D. , Farha Omar K. , Jayaraman Arthi , Shawkey Matthew D. , Gianneschi Nathan C. 
Published: April 2021

AbstractMelanosomes in nature have diverse morphologies, including spheres, rods, and platelets. By contrast, shapes of synthetic melanins have been almost entirely limited to spherical nanoparticles with few exceptions produced by complex templated synthetic methods. Here, we report a non‐templated method to access synthetic melanins with a variety of architectures including spheres, sheets, and platelets. Three 1,8‐dihydroxynaphthalene dimers (4‐4′, 2‐4′ and 2‐2′) were used as self‐assembling synthons. These dimers pack to form well‐defined structures of varying morphologies depending on the isomer. Specifically, distinctive ellipsoidal platelets can be obtained using 4‐4′ dimers. Solid‐state polymerization of the preorganized dimers generates polymeric synthetic melanins while maintaining the initial particle morphologies. This work provides a new route to anisotropic synthetic melanins, where the building blocks are preorganized into specific shapes, followed by solid‐state polymerization.
Silylated Sulfuric Acid: Preparation of a Tris(trimethylsilyl)oxosulfonium [(Me3Si−O)3SO]+ Salt
Authors: Bläsing Kevin , Labbow Rene , Schulz Axel , Villinger Alexander 
Published: April 2021

AbstractThe chemistry of silylated sulfuric acid, O2S(OSiMe3)2 (T2SO4, T=Me3Si; also known as bis(trimethylsilyl) sulfate), has been studied in detail with the aim of synthesizing the formal autosilylation products of silylated sulfuric acid, [T3SO4]+ and [TSO4]−, in analogy to the known protonated species, [H3SO4]+ and [HSO4]−. The synthesis of the [TSO4]− ion only succeeds when a base, such as OPMe3 that forms a weakly coordinating cation upon silylation, is reacted with T2SO4, resulting in the formation of [Me3POT]+[TSO4]−. [T3SO4]+ salts could be isolated starting from T2SO4 in the reaction with [T−H−T]+[B(C6F5)4]− or T+[CHB11Br6H5]− when a weakly coordinating anion is used as counterion. All silylated compounds could be crystallized and structurally characterized.
Grafting multi‐elements hybrid polymer brushes on graphene oxide for epoxy composite with excellent flame retardancy
Authors: Zhang Jiatian , Wu Wenqian , Lv Yan , Guo Chuanluan , Xu Yiting , Zeng Birong , Dai Lizong 
Published: April 2021

AbstractIn this paper, a silicon‐oxygen coupling agent (MPS) with a double bond is hydrolyzed with graphene oxide (GO) to obtain MPS‐GO. The polymerization of MPS‐GO with the phosphorus‐containing monomer (HEPO) is initiated with 2,2′‐Azobis(2‐methylpropionitrile) (AIBN) to obtain multi‐elements hybrid polymer brushes grafting graphene oxide (HM‐GO). As a flame retardant, different amounts of HM‐GO are added to obtain EP composites. In this system, the properties of composite flame retardant obviously increase with the increasing of HM‐GO. The limiting oxygen index (LOI) value of composites with 4 wt% addition of HM‐GO is 31.0%, while the LOI value of EP‐0 is only 23.9%. And the peak heat release rate (PHRR) value is reduced from 515.8 W g−1 of pure epoxy resin to 376.9 W g−1. In addition, with the increase of HM‐GO addition, the Tg value, flexural strength and flexural modulus of EP composites are improved. Through calculation, it is proved that the rising of Tg was due to the increase of crosslink density of the system. The flame retardant performance and mechanical properties of the composite materials are steadily improved, indicating that such flame retardants are dispersed well in the epoxy resin. HM‐GO is an efficient macromolecular modified graphene oxide halogen‐free flame retardant, which can improve both flame retardant properties and mechanical properties.
Structural and biological aspects of natural bridged macrobicyclic peptides from marine resources
Authors: Dahiya Rajiv , Dahiya Sunita , Kumar Priyank , Kumar Radhika V. , Dahiya Saurabh , Kumar Suresh , Saharan Renu , Basu Paramita , Mitra Arindam , Sharma Ajay , Kashaw Sushil K. , Patel Jayvadan K. 
Published: April 2021

AbstractAmong peptide‐based drugs, naturally occurring bicyclic compounds have been established as molecules with unique therapeutic potential. The diverse pharmacological activities associated with bicyclic peptides from marine tunicates, sponges, and bacteria render them suitable to be employed as effective surrogate between complex and small therapeutic moieties. Bicyclic peptides possess greater conformational rigidity and higher metabolic stability as compared with linear and monocyclic peptides. The antibody‐like affinity and specificity of bicyclic peptides enable their binding to the challenging drug targets. Bridged macrobicyclic peptides from natural marine resources represent an underexplored class of molecules that provides promising platforms for drug development owing to their biocompatibility, similarity, and chemical diversity to proteins. The present review explores major marine‐derived bicyclic peptides including disulfide‐bridged, histidinotyrosine‐bridged, or histidinoalanine‐bridged macrobicyclic peptides along with their structural characteristics, synthesis, structure–activity relationship, and bioproperties.The comparison of these macrobicyclic congeners with linear/monocyclic peptides along with their therapeutic potential are also briefly discussed.
High accuracy adaptive motion control for a robotic manipulator with model uncertainties based on multilayer neural network
Authors: Hu Jian , Wang Pengfei , Xu Chenchen , Zhou Haibo , Yao Jianyong 
Published: April 2021

AbstractA robotic manipulator is widely used nowadays, and its high‐accuracy motion control has become a hot topic. However, since it is a very complicated control plant, there exist many structural and unstructured uncertainties in its mathematical model, which would degrade the manipulator control performance when the traditional model‐based control method such as feedback linearization control is adopted. In this paper, a practical method that combines feedback linearization control with multilayer neural network (MNN)‐based model uncertainties observer is proposed for high‐accuracy motion control of a robotic manipulator. The proposed controller not only accounts for the parametric uncertainties but also for the external disturbance. A multilayer neural network capable of online learning is designed to estimate all of the model uncertainties, which can be compensated through the feedforward cancellation technique. A weight adaption law for the online learning neural network is derived based on Lyapunov stability theory. Finally, a feedback linearization method with the MNN‐based observer is designed to stabilize the whole system. The stability proof shows that bounded stability of a manipulator system with the proposed controller is guaranteed. Extensive simulation results show that this control strategy achieves high‐accuracy tracking control in the presence of the manipulator parametric uncertainties and external disturbance.
Controller synthesis for discrete‐time positive switched T–S fuzzy systems with partially controllable subsystems
Authors: Yang Gengjiao , Hao Fei , Zhang Lin , Li Bo hu 
Published: April 2021

AbstractThe controller synthesis problem for discrete‐time positive switched T–S fuzzy systems (PSTSFSs) is investigated in this paper. Unlike previous literature, subsystems are assumed to be partially controllable in this paper. A novel slow–fast combined mode‐dependent average dwell time (SFCMDADT) approach is proposed to obtain sufficient conditions for the stability of general positive switched nonlinear systems with partially stable subsystems. Then based on the obtained results, a parallel distributed compensation (PDC)‐based fuzzy controller is designed, and sufficient conditions for the stability of PSTSFSs with partially controllable subsystems are developed with the aid of a time‐scheduled multiple linear copositive Lyapunov function. Furthermore, sufficient conditions for the stability of the positive switched T–S fuzzy system are given respectively for the two cases that the subsystems are all controllable and all uncontrollable. Finally, two simulation examples are provided to illustrate the effectiveness of the proposed method.
The impact of COVID‐19 on stress, anxiety, and coping in youth with and without autism and their parents
Authors: Corbett Blythe A. , Muscatello Rachael A. , Klemencic Mark E. , Schwartzman Jessica M. 
Published: April 2021

AbstractIn the wake of COVID‐19, the world has become a more uncertain environment—a breeding ground for stress and anxiety, especially for individuals with autism spectrum disorder (ASD). The study examined stress, anxiety, and coping in a data‐driven, real‐time assessment of 122 youth with and without ASD and their parents at the height of the COVID‐19 shutdown and three‐months later. Standardized measures were administered to ascertain stress and coping explicitly related to the pandemic (RSQ COVID‐19‐Child [self‐report], Adult [self‐report from the guardian of youth], Parent [report about child]) and anxiety (STAI‐C, STAI‐A). Multivariate, univariate analyses of variance and hierarchical regression were used. ASD youth endorsed more Trait anxiety and response to specific stressors (e.g., virus). Caregivers of youth with ASD (Adults) self‐reported higher anxiety, yet scores were elevated for both groups. Adults of youth with ASD reported more stress, especially related to the virus, access to healthcare, and concern for the future. In the TD group, youth and adults used more Primary and Secondary Control Coping whereas ASD youth and adults used more Disengagement Coping. Adult stress was the primary predictor of parent perception of child stress as well as Child self‐reported stress. While the ASD group was consistently high compared to the TD group, there were no significant changes over time for stress or anxiety. Results reveal striking differences in youth with ASD and their parents regarding stress, anxiety, and coping. Findings highlight the need for essential support, access to services, and strategies to enhance psychological and emotional well‐being.Lay SummaryThis study examined stress, anxiety, and coping related to the COVID‐19 pandemic in 61 youth with autism spectrum disorder (ASD) and 61 youth with typical development (TD) and their parents. Results showed that ASD youth reported more anxiety and stress. Adults of youth with ASD indicated higher self‐reported anxiety and stress than adults of TD youth. TD youth and their parents reported using more adaptive coping strategies. Findings highlight the need for strategies to enhance psychological and emotional well‐being.
Adsorbed protein film on pump surfaces leads to particle formation during fill‐finish manufacturing
Authors: Roffi Kirk , Li Li , Pantazis Jacob 
Published: April 2021

AbstractDuring fill‐finish manufacturing, therapeutic proteins may aggregate or form subvisible particles in response to the physical stresses encountered within filling pumps. Understanding and quantitating this risk is important since filling may be the last unit operation before the patient receives their dose. We studied particle formation from lab‐scale to manufacturing‐scale using sensitive and robust protein formulations. Filling experiments with a ceramic rotary piston pump were integrated with a rinse‐stripping method to investigate the relationship between protein adsorption and particle formation. For a sensitive protein, multilayer film formation on the piston surface correlated with high levels of subvisible particles in solution. For a robust protein formulation, adsorption and subvisible particle formation were minimal. These results support an aggregation mechanism that is initiated by adsorption to pump surfaces and propagated by mechanical and/or hydrodynamic disruption of the film. The elemental analysis confirmed that ceramic wear debris remained at trace levels and did not contribute appreciably to protein aggregation.
Determination of the Phytochemical Composition and Antioxidant Potential of Eugenia copacabanensis and Myrciaria tenella Leaves (Myrtaceae) Using a Saccharomyces cerevisiae Model
Authors: de Carvalho Martins Víctor , França Liliana Princisval , da Silva Ferreira Yasmim , Pires Daniele Cabral , de Souza Cardoso Bárbara , Pessanha de Araújo Santiago Manuela Cristina , Pacheco Sidney , da Costa Souza Marcelo , Riger Cristiano Jorge , de Oliveira Godoy Ronoel Luiz , Geraldo de Carvalho Mario 
Published: April 2021

AbstractEugenia copacabanensis and Myrciaria tenella are present in restingas of the Atlantic Forest, but little information is available about their chemical and biological potential. In this context, the hexane, dichloromethane, ethyl acetate and butanol fractions from the leaves of methanolic extract were analyzed by GC/MS and HPLC‐DAD and the antioxidant potential was determined by DPPH and ABTS assays and using a Saccharomyces cerevisiae model. Dereplication allowed the identification of 68 compounds, 42 and 41 of which, respectively, are first reported here for E. copacabanensis and M. tenella. In vivo results revealed that the ethyl acetate and butanol fractions showed expressive antioxidant protection in the BY4741 and Δgsh1 strains, with greater impact on glutathione‐deficient cells. With a high diversity of phenolic compounds, these polar fractions of E. copacabanensis and M. tenella leaves are potential protectors against intracellular oxidative stress.
Labeling and Characterization of Phenol‐Containing Glycopeptides Using Chemoselective Probes with Isotope Tags
Authors: Wang Tsung‐Shing Andrew , Wu Ruo‐Yu , Hong Yu , Wang Zhe‐Chong , Li Tsung‐Lin , Shie Jiun‐Jie , Hsu Cheng‐Chih 
Published: April 2021

AbstractSecondary metabolites are structurally diverse natural products (NPs) and have been widely used for medical applications. Developing new tools to enrich NPs can be a promising solution to isolate novel NPs from the native and complex samples. Here, we developed native and deuterated chemoselective labeling probes to target phenol‐containing glycopeptides by the ene‐type labeling used in proteomic research. The clickable azido‐linker was included for further biotin functionalization to facilitate the enrichment of labeled substrates. Afterward, our chemoselective method, in conjunction with LC‐MS and MSn analysis, was demonstrated in bacterial cultures. A vancomycin‐related phenol‐containing glycopeptide was labeled and characterized by our labeling strategy, showing its potential in glycopeptide discovery in complex environments.
Electrochemical Transformations of Methylxanthines in Non‐Aqueous Medium
Authors: Di Matteo Paola , Bortolami Martina , Feroci Marta , Scarano Vincenzo , Petrucci Rita 
Published: April 2021

AbstractCoffee, cocoa and tea are the main sources of the natural methylxanthines caffeine, theobromine and theophylline. They are the most consumed alkaloids worldwide, with both beneficial and harmful effects on health. In addition to more traditional therapeutic uses, beneficial effects related to the oxidative stress have been more recently ascribed to these compounds. Moreover, natural methylxanthines have recently attracted attention as bio‐based and renewable starting materials for organic synthesis. By using the electron as a green and sustainable reagent, organic electrochemistry provides a precious tool to carry out redox reactions for both mechanistic and synthetic purposes. The electrochemistry of natural methylxanthines was studied previously in an aqueous electrolytes, in which their chemistry is closely related to that of uric acid. Conversely, their electrochemistry in organic solvent is recent history: a few but successful examples of organic electrosyntheses and functionalizations have been reported, with promising applications in the pharmaceutical field. Moreover, some advances in molecular mechanisms might shed light on their potentialities as antioxidants. A prospective is given in the present minireview.
Hydrodehalogenation of Polychloromethanes on Silver‐Based Gas Diffusion Electrodes
Authors: Rondinini Sandra , Pargoletti Eleonora , Vertova Alberto , Minguzzi Alessandro 
Published: April 2021

AbstractThis work reports the electroreduction of a volatile organic halide (trichloromethane) from an airborn stream. In the past years, we highlighted the role of polycrystalline silver as powerful electrocatalyst for the electroreductive hydrodehalogenation of volatile organic halides (VOH) in water/organic solvent mixtures, from 0 to 100 % of the aqueous component. The successful conversion of trichloromethane and 1,1,1‐trichloethane to the relevant dehalogenated compounds, methane and ethane have prompted us to extend the investigations to the treatment of gaseous effluents, adopting a silver Gas Diffusion Electrode (Ag‐GDE) and the appropriate cell design. In the field of electroreduction processes the possibility of using GDE to treat gaseous effluents for the removal of volatile organic pollutants represents an electrochemical challenge, and the treatment of N2/CHCl3 gas mixtures fed into the cathodic Ag‐GDE compartment demonstrates the feasibility of the electroreductive detoxification process. Our results will be presented and discussed in terms of CHCl3 removal efficiency, selectivity and energy consumption in preparative electrolyses.
Rational Enzyme Design without Structural Knowledge: A Sequence‐Based Approach for Efficient Generation of Transglycosylases
Authors: Teze David , Zhao Jiao , Wiemann Mathias , Kazi Zubaida G. A. , Lupo Rossana , Zeuner Birgitte , Vuillemin Marlène , Rønne Mette E. , Carlström Göran , Duus Jens Ø. , Sanejouand Yves‐Henri , O'Donohue Michael J. , Nordberg Karlsson Eva , Fauré Régis , Stålbrand Henrik , Svensson Birte 
Published: April 2021

AbstractGlycobiology is dogged by the relative scarcity of synthetic, defined oligosaccharides. Enzyme‐catalysed glycosylation using glycoside hydrolases is feasible but is hampered by the innate hydrolytic activity of these enzymes. Protein engineering is useful to remedy this, but it usually requires prior structural knowledge of the target enzyme, and/or relies on extensive, time‐consuming screening and analysis. Here, a straightforward strategy that involves rational rapid in silico analysis of protein sequences is described. The method pinpoints 6–12 single‐mutant candidates to improve transglycosylation yields. Requiring very little prior knowledge of the target enzyme other than its sequence, the method is generic and procures catalysts for the formation of glycosidic bonds involving various d/l‐, α/β‐pyranosides or furanosides, and exo or endo action. Moreover, mutations validated in one enzyme can be transposed to others, even distantly related enzymes.
Porous Tungsten Oxide: Recent Advances in Design, Synthesis, and Applications
Authors: Bentley John , Desai Salil , Bastakoti Bishnu Prasad 
Published: April 2021

AbstractTungsten oxide (WO3) has received ever more attention and has been highly researched over the last decade due to its being a low‐cost transition metal semiconductor with tunable, yet widely stable, band gaps. This minireview briefly highlights the challenges in the design and synthesis of porous WO3 including methods, precursors, solvent effects, crystal phases, and surface activities of the porous WO3 base material. These topics are explored while also drawing a connection of how the morphology and crystal phase affect the band gap. The shifts in band gap not only impact the optical properties of tungsten but also allow tuning to operate on different energy levels, which makes WO3 highly desirable in many applications such as supercapacitors, batteries, solar cells, catalysts, sensors, smart windows, and bioapplications.
Low‐Temperature Direct Electrochemical Methanol Reforming Enabled by CO‐Immune Mo‐Based Hydrogen Evolution Catalysts
Authors: Bau Jeremy A. , Rueping Magnus 
Published: April 2021

AbstractHydrogen storage in the form of intermediate artificial fuels such as methanol is important for future chemical and energy applications, and the electrochemical regeneration of hydrogen from methanol is thermodynamically favorable compared to direct water splitting. However, CO produced from methanol oxidation can adsorb to H2‐evolution catalysts and drastically reduce activity. In this study, we explore the origins of CO immunity in Mo‐containing H2‐evolution catalysts. Unlike conventional catalysts such as Pt or Ni, Mo‐based catalysts display remarkable immunity to CO poisoning. The origin of this behavior in NiMo appears to arise from the apparent inability of CO to bind Mo under electrocatalytic conditions, with mechanistic consequences for the H2‐evolution reaction (HER) in these systems. This specific property of Mo‐based HER catalysts makes them ideal in environments where poisons might be present.
Co3O4−CeO2 Nanocomposites for Low‐Temperature CO Oxidation
Authors: Yang Jingxia , Yigit Nevzat , Möller Jury , Rupprechter Günther 
Published: April 2021

AbstractIn an effort to combine the favorable catalytic properties of Co3O4 and CeO2, nanocomposites with different phase distribution and Co3O4 loading were prepared and employed for CO oxidation. Synthesizing Co3O4‐modified CeO2 via three different sol‐gel based routes, each with 10.4 wt % Co3O4 loading, yielded three different nanocomposite morphologies: CeO2‐supported Co3O4 layers, intermixed oxides, and homogeneously dispersed Co. The reactivity of the resulting surface oxygen species towards CO were examined by temperature programmed reduction (CO‐TPR) and flow reactor kinetic tests. The first morphology exhibited the best performance due to its active Co3O4 surface layer, reducing the light‐off temperature of CeO2 by about 200 °C. In contrast, intermixed oxides and Co‐doped CeO2 suffered from lower dispersion and organic residues, respectively. The performance of Co3O4‐CeO2 nanocomposites was optimized by varying the Co3O4 loading, characterized by X‐ray diffraction (XRD) and N2 sorption (BET). The 16–65 wt % Co3O4−CeO2 catalysts approached the conversion of 1 wt % Pt/CeO2, rendering them interesting candidates for low‐temperature CO oxidation.