bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ein neuer Aufbau zur Untersuchung der Struktur und Funktion von solvatisierten, lyophilisierten und kristallinen Metalloenzymen – veranschaulicht anhand von [NiFe]‐Hydrogenasen
Authors: Lorent Christian , Pelmenschikov Vladimir , Frielingsdorf Stefan , Schoknecht Janna , Caserta Giorgio , Yoda Yoshitaka , Wang Hongxin , Tamasaku Kenji , Lenz Oliver , Cramer Stephen P. , Horch Marius , Lauterbach Lars , Zebger Ingo 
Published: March 2021

AbstractZur Untersuchung von Metalloenzymen haben wir einen Aufbau für die Präparation katalytischer Intermediate und deren anschließende Charakterisierung mit spektroskopischen Techniken entwickelt. Mit diesem können Redoxreaktionen in Enzymen in Form von Lyophilisat, gelöst oder als Kristall in einem großen Temperaturbereich IR‐spektroskopisch in situ verfolgt werden. Zwei sauerstofftolerante [NiFe]‐Hydrogenasen wurden als Modellenzyme untersucht. Zunächst wurde der Aufbau zur Herstellung von komprimiertem Lyophilisat einer Hydrogenase in einem paramagnetischen Zustand mit verbrückendem Hydrid genutzt. Dies erleichterte die Charakterisierung durch57Fe‐kernresonante inelastische Streuung und erlaubte es, in Kombination mit DFT, die schwingungsspektroskopischen Merkmale dieses katalytischen Intermediats zu detektieren. Der In‐situ‐IR‐Aufbau lieferte zusammen mit Resonanz‐Raman‐Untersuchungen auch Einblicke in die Redoxchemie von Proteinkristallen. Eine Ergänzung röntgenkristallographischer Daten durch komplementäre spektroskopische Analysen ist daher essentiell.
Ion Mobility Mass Spectrometry Uncovers Guest‐Induced Distortions in a Supramolecular Organometallic Metallosquare
Authors: Vicent Cristian , Martinez‐Agramunt Victor , Gandhi Viraj , Larriba‐Andaluz Carlos , Gusev Dmitry G. , Peris Eduardo 
Published: March 2021

AbstractThe encapsulation of the tetracationic palladium metallosquare with four pyrene‐bis‐imidazolylidene ligands [1]4+with a series of organic molecules was studied by Electrospray ionization Travelling Wave Ion‐Mobility Mass Spectrometry (ESI TWIM‐MS). The method allowed to determine the Collision Cross Sections (CCSs), which were used to assess the size changes experienced by the host upon encapsulation of the guest molecules. When fullerenes were used as guests, the host is expanded ΔCCS 13 Å2and 23 Å2, for C60or C70, respectively. The metallorectangle [1]4+was also used for the encapsulation of a series of polycyclic aromatic hydrocarbons (PAHs) and naphthalenetetracarboxylic diimide (NTCDI), to form complexes of formula [(NTCDI)2(PAH)@1]4+. For these host:guest adducts, the ESI IM‐MS studies revealed that [1]4+is expanded by 47–49 Å2.. The energy‐minimized structures of [1]4+, [C60@1]4+, [C70@1]4+, [(NTCDI)2(corannulene)@1]4+in the gas phase were obtained by DFT calculations.Introduction
25 Jahre retikuläre Chemie
Authors: Freund Ralph , Canossa Stefano , Cohen Seth M. , Yan Wei , Deng Hexiang , Guillerm Vincent , Eddaoudi Mohamed , Madden David G. , Fairen‐Jimenez David , Lyu Hao , Macreadie Lauren K. , Ji Zhe , Zhang Yuanyuan , Wang Bo , Haase Frederik , Wöll Christof , Zaremba Orysia , Andreo Jacopo , Wuttke Stefan , Diercks Christian S. 
Published: March 2021

AbstractIm Wesentlichen hat die retikuläre Chemie die Präzision und Expertise der organischen und anorganischen Synthese auf den festen Zustand übertragen. Während die anfängliche Aufregung über Metall‐organische Gerüstverbindungen (MOFs) und kovalente organische Gerüstverbindungen (COFs) zweifellos durch ihre beispiellose Porosität und Oberfläche befeuert wurde, war die tiefgreifendste wissenschaftliche Innovation des Feldes die Ausarbeitung von Designstrategien für die Synthese von erweiterten kristallinen Festkörpern durch starke gerichtete Bindungen. In diesem Aufsatz beleuchten wir die verschiedenen Klassen von retikulären Materialien, die entwickelt worden sind, wie solche Gerüstverbindungen funktionalisiert werden können und wie Komplexität in ihr Grundgerüst eingeführt werden kann. Schließlich zeigen wir, wie die strukturelle Kontrolle über diese Materialien von der molekularen Skala über ihre Kristallmorphologie und Form auf der Nanoskala bis hin zu ihrer Gestaltung auf der Bulk‐Skala erweitert wird.
Structural and Functional Analyses of the Tridomain‐Nonribosomal Peptide Synthetase FmoA3 for 4‐Methyloxazoline Ring Formation
Authors: Katsuyama Yohei , Sone Kaoru , Harada Ayaka , Kawai Seiji , Urano Naoki , Adachi Naruhiko , Moriya Toshio , Kawasaki Masato , Shin‐ya Kazuo , Senda Toshiya , Ohnishi Yasuo 
Published: March 2021

AbstractNonribosomal peptide synthetases (NRPSs) are attractive targets for bioengineering to generate useful peptides. FmoA3 is a single modular NRPS composed of heterocyclization (Cy), adenylation (A), and peptidyl carrier protein (PCP) domains. It uses α‐methyl‐l‐serine to synthesize a 4‐methyloxazoline ring, probably with another Cy domain in the preceding module FmoA2. Here, we determined the head‐to‐tail homodimeric structures of FmoA3 by X‐ray crystallography (apo‐form, with adenylyl‐imidodiphosphate and α‐methyl‐l‐seryl‐AMP) and cryogenic electron microscopy single particle analysis, and performed site‐directed mutagenesis experiments. The data revealed that α‐methyl‐l‐serine can be accommodated in the active site because of the extra space around Ala688. The Cy domains of FmoA2 and FmoA3 catalyze peptide bond formation and heterocyclization, respectively. FmoA3’s Cy domain seems to lose its donor PCP binding activity. The collective data support a proposed catalytic cycle of FmoA3.
Halide Replacement with Complete Preservation of Crystal Lattice in Mixed‐Anion Lanthanide Oxyhalides
Authors: Udayakantha Malsha , Handy Joseph V. , Davidson Rachel D. , Kaur Jagjit , Villalpando Graciela , Zuin Lucia , Chakraborty Sudip , Banerjee Sarbajit 
Published: March 2021

AbstractA challenge in anion control in periodic solids is to preserve the crystal lattice while substituting for different anions of widely varying size and hardness. Post‐synthetic modification routes that place cations or anions in non‐equilibrium configurations are promising; however, such methods remain relatively unexplored for anion placement. Here, we report the synthesis of LaOI nanocrystals by a non‐hydrolytic sol‐gel condensation reaction and their transformation into LaOBr, LaOCl, and LaOF nanocrystals along hard–soft acid–base principles using post‐synthetic metathesis reactions with ammonium halides. Anion displacement proceeds along halide planes, preserving the tetragonal matlockite structure. Energy‐variant X‐ray excited optical luminesce signatures of alloyed Tb3+‐ions is a sensitive quantum reporter of the preservation of the cation sublattice and hardening of the crystal structure upon anion replacement.
Bicyclic β‐Sheet Mimetics that Target the Transcriptional Coactivator β‐Catenin and Inhibit Wnt Signaling
Authors: Wendt Mathias , Bellavita Rosa , Gerber Alan , Efrém Nina‐Louisa , van Ramshorst Thirza , Pearce Nicholas M. , Davey Paul R. J. , Everard Isabel , Vazquez‐Chantada Mercedes , Chiarparin Elisabetta , Grieco Paolo , Hennig Sven , Grossmann Tom N. 
Published: March 2021

AbstractProtein complexes are defined by the three‐dimensional structure of participating binding partners. Knowledge about these structures can facilitate the design of peptidomimetics which have been applied for example, as inhibitors of protein–protein interactions (PPIs). Even though β‐sheets participate widely in PPIs, they have only rarely served as the basis for peptidomimetic PPI inhibitors, in particular when addressing intracellular targets. Here, we present the structure‐based design of β‐sheet mimetics targeting the intracellular protein β‐catenin, a central component of the Wnt signaling pathway. Based on a protein binding partner of β‐catenin, a macrocyclic peptide was designed and its crystal structure in complex with β‐catenin obtained. Using this structure, we designed a library of bicyclic β‐sheet mimetics employing a late‐stage diversification strategy. Several mimetics were identified that compete with transcription factor binding to β‐catenin and inhibit Wnt signaling in cells. The presented design strategy can support the development of inhibitors for other β‐sheet‐mediated PPIs.
Enhanced Supercapacitor Performance Using a Co3O4@Co3S4 Nanocomposite on Reduced Graphene Oxide/Ni Foam Electrodes
Authors: Ansarinejad Hanieh , Shabani‐Nooshabadi Mehdi , Ghoreishi Sayed Mehdi 
Published: March 2021

AbstractTo avoid an enormous energy crisis in the not‐too‐distant future, it be emergent to establish high‐performance energy storage devices such as supercapacitors. For this purpose, a three‐dimensional (3D) heterostructure of Co3O4 and Co3S4 on nickel foam (NF) that is covered by reduced graphene oxide (rGO) has been prepared by following a facile multistep method. At first, rGO nanosheets are deposited on NF under mild hydrothermal conditions to increase the surface area. Subsequently, nanowalls of cobalt oxide are electro‐deposited on rGO/Ni foam by applying cyclic‐voltammetry (CV) under optimized conditions. Finally, for the synthesis of Co3O4@Co3S4 nanocomposite, the nanostructure of Co3S4 was fabricated from Co3O4 nanowalls on rGO/NF by following an ordinary hydrothermal process through the sulfurization for the electrochemical application. The samples are characterized by using X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The obtained sample delivers a high capacitance of 13.34 F cm−2 (5651.24 F g−1) at a current density of 6 mA cm−2 compared to the Co3O4/rGO/NF electrode with a capacitance of 3.06 F cm−2 (1230.77 F g−1) at the same current density. The proposed electrode illustrates the superior electrochemical performance such as excellent specific energy density of 85.68 W h Kg−1, specific power density of 6048.03 W kg−1 and a superior cycling performance (86% after 1000 charge/discharge cycles at a scan rate of 5 mV s−1). Finally, by using Co3O4 @Co3S4/rGO/NF and the activated carbon‐based electrode as positive and negative electrodes, respectively, an asymmetric supercapacitor (ASC) device was assembled. The fabricated ASC provides an appropriate specific capacitance of 79.15 mF cm−2 at the applied current density of 1 mA cm−2, and delivered an energy density of 0.143 Wh kg−1 at the power density of 5.42 W kg−1.
Rapid optimization of processes for the integrated purification of biopharmaceuticals
Authors: Crowell Laura E. , Rodriguez Sergio A. , Love Kerry R. , Cramer Steven M. , Love J. Christopher 
Published: March 2021

AbstractStraight‐through chromatography, wherein the eluate from one column passes directly onto another column without adjustment, is one strategy to integrate and intensify manufacturing processes for biologics. Development and optimization of such straight‐through chromatographic processes is a challenge, however. Conventional high‐throughput screening methods optimize each chromatographic step independently, with limited consideration for the connectivity of steps. Here, we demonstrate a method for the development and optimization of fully integrated, multi‐column processes for straight‐through purification. Selection of resins was performed using an in silico tool for the prediction of processes for straight‐through purification based on a one‐time characterization of host‐cell proteins combined with the chromatographic behavior of the product. A two‐step optimization was then conducted to determine the buffer conditions that maximized yield while minimizing process‐ and product‐related impurities. This optimization of buffer conditions included a series of range‐finding experiments on each individual column, similar to conventional screening, followed by the development of a statistical model for the fully integrated, multi‐column process using design of experiments. We used this methodology to develop and optimize integrated purification processes for a single‐domain antibody and a cytokine, obtaining yields of 88% and 86%, respectively, with process‐ and product‐related variants reduced to phase‐appropriate levels for nonclinical material.
Equity through innovation in teaching and learning: A student‐centered approach to systemwide implementation of direct assessment CBE
Authors: Lowe Aisha , Leal‐Carrillo Nadia , Guiney Chantee , Diaz Amparo 
Published: March 2021

AbstractThe California Community Colleges (CCC) system has adopted an equity‐imperative approach to systemic reforms. As part of this effort, and to meet the state's workforce demands of the future, the system has focused on better serving the needs of adult learners, those between the ages of 25 and 64 with some college but no degree. The current impact of COVID‐19 has exacerbated the inequitable learning experiences of minoritized students and has forced the system to reimagine teaching and learning, with urgency. With a heightened focus on access, persistence, and the success of CCC students, direct assessment competency‐based education (CBE) through self‐paced learning, high‐touch and high‐tech student support is a clear next step in the evolution of teaching and learning to meet the needs of adult learners. This paper discusses the impetus for such innovation and the CCC system's effort to add direct assessment CBE to its educational offerings.
Electrocatalytic Hydrogen Evolution Catalyzed by 3,4‐Toluenedithiolate Nickel Complexes of Bis(diphenylphosphine)amine Ligand Containing An Azahydrophilic Group
Authors: Li Tao , Xie Bin , Zhang Dongliang , Lai Chuan , Li Xiaolong , Mou Wenyu , Cao Jiaxi , Bai Xiaoxue , Chen Luo 
Published: March 2021

AbstractTwo 3,4‐toluenedithiolate nickel complexes of bis(diphenylphosphine)amine ligand containing an azahydrophilic group, [(CH3)2N(CH2)2N(PPh2)2Ni(tdt)] (1) and [(CH3)2N+Bz(CH2)2N(PPh2)2Ni(tdt)] Br− (2) (tdt=3,4‐toluenedithiolate, Bz=PhCH2), have been synthesized and characterized by elemental analysis and spectroscopy (FTIR, UV‐vis, 1H, and 31P{1H} NMR). The electrochemical property of 1 and 2 was investigated in MeCN and MeCN/H2O, respectively. The redox potentials of 1 and 2 are shifted to less‐negative potentials as the water contents increase in MeCN/H2O, in which the first reduction potentials for 1 and 2 are shifted positively by 160 and 140 mV in 7 : 3 MeCN/H2O in compassion to neat MeCN. 1 and 2 exhibit the electrocatalysis for hydrogen (H2) evolution using trifluoroacetic acid (TFA) as the proton source both in MeCN and in MeCN/H2O. Remarkably, 1 and 2 display favorable energetics towards electrocatalytic proton reduction in the presence of water, and the more hydrophilic quaternary ammonium group is beneficial to enhance the catalytic activity for 2. A CEEC (C is a chemical step protonation and E is the electrochemical step reduction) electrocatalytic mechanism for hydrogen production by 1 was proposed in MeCN, where the catalyst 1 firstly undergo rapidly protonation at the coordinating S1 atom in the tdt ligand to generate intermediate [NiIIS1‐H]+ before undergoing reduction, and the reduction of [NiIIS1‐H]+ yields a key metal hydride species, [NiIII‐H]. Theoretical calculations carried out using density functional theory (DFT) which is consistent with the proposed catalytic reaction mechanism for 1.
Modeling of the Pervaporation for Dehydration of Dimethyl Aminoethyl Azide by Ceramic Composite Membranes
Authors: Alikamar Mitra Rezaei , Pakdehi Shahram G. 
Published: March 2021

AbstractPervaporation as a membrane process is applied for dehydration of organic mixtures. The performance of a composite ceramic membrane was assessed in the pervaporation process for dehydration of dimethyl aminoethyl azide (DMAZ) solution under different operational conditions. The system behavior was modeled, and the model solved numerically with the finite element method via COMSOL software. Good verification in experimental and modeling results was observed with calculated errors of less than 2 %.
Preparation and Properties of Benzylsulfonyl‐Containing Silicone Copolymers via Ring‐opening Copolymerization of Macroheterocyclosiloxane and Cyclosiloxane
Authors: Guo Mengdong , Huang Yue , Chen Zhongkai , Zhang Yangping , Zhang Ya , Zhu Mingquan , Zhang Jie , Feng Shengyu 
Published: March 2021

AbstractRing‐opening copolymerization (ROCP) of benzylsulfonyl macroheterocyclosiloxane (BSM) and five different cyclosiloxanes was systematically investigated. A general approach for the synthesis of benzylsulfonyl‐containing silicone copolymers with various substituents, including methyl, vinyl, ethyl, and phenyl, was developed herein. A series of copolymers with variable incorporation (from 6 % to 82 %) of BSM were obtained by modifying the comonomer feed ratio and using KOH as the catalyst in a mixed solvent of dimethylformamide and toluene. The obtained copolymers exhibited various composition‐dependent properties and unique viscoelasticity. Notably, the surface and fluorescent characteristics as well as the glass transition temperatures of the copolymers could be tailored by varying the amount of BSM. Unlike typical sulfone‐containing polymers, such as poly(olefin sulfone)s, the prepared copolymers displayed excellent thermal and hydrolytic stability. The universal strategy developed in the present study provides a platform for the design of innovative silicone copolymers with adjustable structures and performance.
Mechanistic and Kinetic Factors of ortho‐Benzyne Formation in Hexadehydro‐Diels‐Alder (HDDA) Reactions
Authors: Maier Jan , Marder Todd B. 
Published: March 2021

AbstractWith the rapid development of the hexadehydro‐Diels‐Alder reaction (HDDA) from its first discovery in 1997, the question of whether a concerted or stepwise mechanism better describes the thermally activated formation of ortho‐benzyne from a diyne and a diynophile has been debated. Mechanistic and kinetic investigations were able to show that this is not a black or white situation, as minor changes can tip the balance. For that reason, especially, linked yne‐diynes were studied to examine steric, electronic, and radical‐stabilizing effects of their terminal substituents on the reaction mechanism and kinetics. Furthermore, the influence of the nature of the linker on the HDDA reaction was explored. The more recently discovered photochemical HDDA reaction also gives ortho‐arynes, which display the same reactivity as the thermally generated ones, but their formation might not proceed by the same mechanism. This minireview summarizes the current state of mechanistic understanding of the HDDA reaction.
Unveiling the Hidden σ‐Dimerization of a Kinetically Protected Olympicenyl Radical
Authors: Xiang Qin , Xu Jun , Guo Jing , Dang Yanfeng , Xu Zhanqiang , Zeng Zebing , Sun Zhe 
Published: March 2021

AbstractThe σ‐dimer of a kinetically protected olympicenyl radical, which evaded the experimental detection, was revealed by conversion into biolympicenylidene with E‐configuration in a regioselective manner. The complicated stereochemistry and energetics of the σ‐dimers derived from C2v symmetry and uneven spin distribution of the olympicenyl radical were revealed by the theoretical calculations, and the energetic preference of π‐dimer over σ‐dimer by a minute gap was disclosed. The E‐biolympicenylidene, a polycyclic ene structure previously considered as reactive intermediate in the phenalenyl radical system, exhibited exceptional stability, which allowed for a detailed investigation on its singlet diradical character and physical properties by means of X‐ray crystallography, UV‐vis‐NIR absorption/emission spectroscopy and cyclic voltammetry, and assisted by theoretical calculations. The E‐biolympicenylidene showed high resistance towards both thermal and photochemical ring‐cyclization reactions, which was attributed to high activation energies for the rate‐determining electrocyclization operated on both disrotatory and conrotatory mode, as well as a small spin density at the bonding sites for the radical‐radical coupling process.
Total Syntheses and Chemical Biology Studies of Hymeglusin and Fusarilactone A, Novel Circumventors of β‐Lactam Drug Resistance in Methicillin‐Resistant Staphylococcus aureus
Authors: Kanaida Masahiro , Kimishima Aoi , Eguchi Shuhei , Iwatsuki Masato , Watanabe Yoshihiro , Honsho Masako , Hirose Tomoyasu , Noguchi Yoshihiko , Nonaka Kenichi , Sennari Goh , Matsui Hidehito , Kaito Chikara , Hanaki Hideaki , Asami Yukihiro , Sunazuka Toshiaki 
Published: March 2021

AbstractHymeglusin, a previously known eukaryotic hydroxymethylglutaryl‐CoA (HMG−CoA) synthase inhibitor, was identified as circumventing the β‐lactam drug resistance in methicillin‐resistant Staphylococcus aureus (MRSA). We describe the concise total syntheses of a series of natural products, which enabled determination of the absolute configuration of fusarilactone A and provided structure‐activity relationship information. Based on previous reports, we speculated that the target protein of this circumventing effect may be MRSA bacterial HMG−CoA synthase (mvaS). We found that this enzyme was dose‐dependently inhibited by hymeglusin. Furthermore, overexpression of the MRSA mvaS gene and site‐directed mutagenesis studies suggested its binding site and the mechanism of action.
Investigating the effect of mouth guard use on aerobic performance in amateur boxers
Authors: Ahmed Irfan , Kipps Courtney , Fine Peter 
Published: March 2021

AbstractObjectivesTo assess if wearing a mouth guard impacts maximal aerobic capacity in amateur boxers.Materials and MethodsA prospective crossover cohort (pilot) study was conducted to assess maximal aerobic capacity in amateur boxers using the 20 m multi stage fitness test (MSFT). Two primary outcomes measures were recorded: (1) the maximum oxygen uptake (peak VO2—mL/kg/min) and (2) distance run (meters—m). Thirteen amateur boxers completed the MSFT 7 days apart under control (no mouth guard—C) and intervention conditions (mouth guard—MG). Participants also submitted data on height, weight, type of mouth guard and Rate of Perceived Exertion (RPE) during the test.StatisticsPaired T‐test.ResultsMouth guard use was shown to reduce peak VO2 and distance run during the 20 m MSFT from 56.31 to 54.12 mL/kg/min and 2572 to 2380 m respectively (p < 0.05). Twelve out of 13 participants wore a Boil & Bite mouthguard and recorded lower peak VO2 scores (−4.38%) when wearing a mouth guard compared to control conditions, (Mean = −2.46 mL/kg/min, Range of decrease = 4.2–0.9 mL/kg/min; p < 0.05). Ten participants submitted data on RPE—One participant with a custom made mouthguard reported no change in RPE in mouthguard conditions, while nine participants reported an average (+30.5%) increase in mean RPE in Boil & Bite mouthguard conditions compared to control conditions.ConclusionsBoil & Bite mouth guard use was shown to significantly reduce aerobic performance in amateur boxers and increase the perceived rate of exertion during the 20 m MSFT.