2,881 results match your criteria catalysis electrostatic

Structure and Reactivity of N-Heterocyclic Alkynyl Hypervalent Iodine Reagents.

Chemistry 2021 May 12. Epub 2021 May 12.

Ecole Polytechnique Federale de Lausanne, ISIC - Laboratory of Catalysis and Organic Synthesis, EPFL BCH 4306 Batiment chimie UNIL, 1015, Lausanne, SWITZERLAND.

Ethynylbenziodoxol(on)e (EBX) cyclic hypervalent iodine reagents have become popular reagents for the alkynylation of radicals and nucleophiles, but only offer limited possibilities for further structure and reactivity fine-tuning. Herein, we report the synthesis of new N -heterocyclic hypervalent iodine reagents with increased structural flexibility based on amide, amidine and sulfoximine scaffolds. Solid state structures of the reagents are reported and the analysis of the I-C alkyne bond lengths allowed assessing the trans -effect of the different substituents. Read More

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Electrostatic perturbations from the protein affect C-H bond strengths of the substrate and enable negative catalysis in the TmpA biosynthesis enzyme.

Chemistry 2021 May 12. Epub 2021 May 12.

University of Manchester, Manchester Institute of Biotechnology, 131 Princess Street, M1 7DN, Manchester, UNITED KINGDOM.

The nonheme iron dioxygenase 2-(trimethylammonio)-ethylphosphonate dioxygenase (TmpA) is an enzyme involved in the regio- and chemoselective hydroxylation at the C 1 -position of the substrate as part of the biosynthesis of glycine betaine in bacteria and carnitine in humans. To understand how the enzyme avoids breaking the weak C 2 -H bond in favor of C 1 -hydroxylation, we set up a cluster model of 242 atoms representing the first and second-coordination sphere of the metal center and substrate binding pocket and investigated possible reaction mechanisms of substrate activation by an iron(IV)-oxo species by density functional theory methods. In agreement with experimental product distributions, the calculations predict a favorable C 1 -hydroxylation pathway. Read More

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Testing the Limitations of MD-Based Local Electric Fields Using the Vibrational Stark Effect in Solution: Penicillin G as a Test Case.

J Phys Chem B 2021 May 26;125(17):4415-4427. Epub 2021 Apr 26.

Department of Chemistry, Stanford University, Stanford, California 94305-5012, United States.

Noncovalent interactions underlie nearly all molecular processes in the condensed phase from solvation to catalysis. Their quantification within a physically consistent framework remains challenging. Experimental vibrational Stark effect (VSE)-based solvatochromism can be combined with molecular dynamics (MD) simulations to quantify the electrostatic forces in solute-solvent interactions for small rigid molecules and, by extension, when these solutes bind in enzyme active sites. Read More

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Glutamate Mediates Proton-Coupled Electron Transfer Between Tyrosines 730 and 731 in Ribonucleotide Reductase.

J Am Chem Soc 2021 Apr 15;143(16):6054-6059. Epub 2021 Apr 15.

Department of Chemistry, Yale University, 225 Prospect Street, New Haven, Connecticut 06520, United States.

Ribonucleotide reductase (RNR) is an essential enzyme in DNA synthesis for all living organisms. It reduces ribonucleotides to the corresponding deoxyribonucleotides by a reversible radical transfer mechanism. The active form of Ia RNR is composed of two subunits, α and β, which form an active asymmetric αβ complex. Read More

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In-Cell Characterization of the Stable Tyrosyl Radical in E. coli Ribonucleotide Reductase via Advanced EPR Spectroscopy.

Angew Chem Int Ed Engl 2021 Apr 12. Epub 2021 Apr 12.

Technische Universitat Dortmund, Chemistry and Chemical Biology, Otto-Hahn-Strasse 6, 44227, Dortmund, GERMANY.

The E. coli ribonucleotide reductase (RNR), a paradigm for class Ia enzymes including human RNR, catalyzes the biosynthesis of DNA building blocks and requires a di-iron tyrosyl radical (Y122•) cofactor for activity. The knowledge on in vitro Y122• structure and its radical distribution within ß2 subunit has accumulated over the years; yet, little information exists on in vivo Y122•. Read More

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Iodine-Substituted Lithium/Sodium -Decaborates: Syntheses, Characterization, and Solid-State Ionic Conductivity.

ACS Appl Mater Interfaces 2021 Apr 6;13(15):17554-17564. Epub 2021 Apr 6.

Henan Key Laboratory of Boron Chemistry and Advanced Energy Materials, School of Chemistry and Chemical Engineering, Henan Normal University, Xinxiang, Henan 453007, China.

Solid-state electrolytes based on -decaborates have caught increasing interest owing to the impressive room-temperature ionic conductivity, remarkable thermal/chemical stability, and excellent deformability. In order to develop new solid-state ion conductors, we investigated the influence of iodine substitution on the thermal, structural, and ionic conduction properties of -decaborates. A series of iodinated -decaborates, M[BHI] (M = Li, Na; = 1, 2, 10), were synthesized and characterized by thermal analysis, powder X-ray diffraction, and electrochemical impedance spectroscopy; the stability and ionic conductivity of these compounds were studied. Read More

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Crystal Structure of a Phospholipase D from the Plant-Associated Bacteria Strain AS9 Reveals a Unique Arrangement of Catalytic Pocket.

Int J Mol Sci 2021 Mar 22;22(6). Epub 2021 Mar 22.

School of Food Science and Engineering, South China University of Technology, Guangzhou 510640, China.

Phospholipases D (PLDs) play important roles in different organisms and in vitro phospholipid modifications, which attract strong interests for investigation. However, the lack of PLD structural information has seriously hampered both the understanding of their structure-function relationships and the structure-based bioengineering of this enzyme. Herein, we presented the crystal structure of a PLD from the plant-associated bacteria strain AS9 (SpPLD) at a resolution of 1. Read More

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Efficient Photoinduced Energy and Electron Transfers in a Tetraphenylethene-Based Octacationic Cage Through Host-Guest Complexation.

ACS Appl Mater Interfaces 2021 Apr 30;13(14):16837-16845. Epub 2021 Mar 30.

College of Chemistry and Materials Science, Northwest University, Xi'an 710069, P. R. China.

Artificial photofunctional systems with energy and electron transfer functions, inspired from photosynthesis in nature, have been developed for many promising applications including solar cell, biolabeling, photoelectric materials, and photodriven catalysis. Supramolecular hosts including macrocycles and cages have been explored for simulating photosynthesis based on a host-guest strategy. Herein, we report a host-guest approach by using a tetraphenylethene-based octacationic cage and fluorescent dyes to construct artificial photofunctional systems with energy and electron transfer functions. Read More

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Differences in exopolysaccharides of three microbial aggregates.

Environ Technol 2021 Apr 5:1-13. Epub 2021 Apr 5.

National Base of International Science and Technology Cooperation for Intelligent Manufacturing Service, Chongqing Key Laboratory of Catalysis & New Environmental Materials, Chongqing Technology and Business University, Chongqing, People's Republic of China.

Different microbial aggregates show substantial differences in morphology, and extracellular polymer substances have been confirmed to play a key role in the formation of aggregates. In this study, three different microbial aggregates and their exopolysaccharides were compared. The results show that the granular sludge was largest in size and the most compact in shape. Read More

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Dynamic metallization of spherical DNA via conformational transition into gold nanostructures with controlled sizes and shapes.

J Colloid Interface Sci 2021 Jul 10;594:160-172. Epub 2021 Mar 10.

Department of Materials Science and Engineering, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul 02841, Republic of Korea. Electronic address:

Despite the reversible condensation properties of DNA, DNA metallization during controlled conformational transitions has been rarely investigated. We perform dynamic metallization of spherically condensed DNA nanoparticles (DNA NPs) via a globule-to-coil transition. A positively charged new Au reagent is prepared via ligand-exchange of conventional complex Au ions, which was used to synthesize spherically condensed DNA NPs simply based on the fundamental electrostatic and coordinative interactions between DNA and Auions. Read More

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An effective computational-screening strategy for simultaneously improving both catalytic activity and thermostability of α-l-rhamnosidase.

Biotechnol Bioeng 2021 Mar 20. Epub 2021 Mar 20.

College of Food and Biological Engineering, Jimei University, Xiamen, China.

Catalytic efficiency and thermostability are the two most important characteristics of enzymes. However, it is always tough to improve both catalytic efficiency and thermostability of enzymes simultaneously. In the present study, a computational strategy with double-screening steps was proposed to simultaneously improve both catalysis efficiency and thermostability of enzymes; and a fungal α-l-rhamnosidase was used to validate the strategy. Read More

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Hydrogen bonding catalysis by water in epoxide ring opening reaction.

J Mol Graph Model 2021 Jun 5;105:107894. Epub 2021 Mar 5.

Department of Biotechnology and BJM School of Biosciences, Indian Institute of Technology Madras, Chennai, 600036, India. Electronic address:

Water can act as catalyst is perhaps the most intriguing property reported of this molecule in the last decade. However, despite being an integral part of many enzyme structures, the role of water in catalyzing enzymatic reactions remains sparsely studied. In a recent study, we have shown that the epoxide ring opening in aspartate proteases follows a two-step process involving water. Read More

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Mechanistic insight on the inhibition of D, D-carboxypeptidase from by -lactam antibiotics: an ONIOM acylation study.

J Biomol Struct Dyn 2021 Mar 15:1-11. Epub 2021 Mar 15.

Catalysis and Peptide Research Unit, School of Health Sciences, University of KwaZulu-Natal, Durban, South Africa.

cell wall is intricate and impermeable to many agents. A D, D-carboxypeptidase (DacB1) is one of the enzymes involved in the biosynthesis of cell wall peptidoglycan and catalyzes the terminal D-alanine cleavage from pentapeptide precursors. Catalytic activity and mechanism by which DacB1 functions is poorly understood. Read More

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Fingerprinting the Ammonia Synthesis Pathway Using Spatiotemporal Electrostatic Potential Distribution of Intermediates.

ACS Omega 2021 Mar 25;6(9):6292-6296. Epub 2021 Feb 25.

Department of Chemical, Biomolecular, and Corrosion Engineering, The University of Akron, Akron, Ohio 44325, United States.

It remains a research challenge in determining the catalytic reaction mechanisms primarily caused by the difficulty to experimentally identify active intermediates with current analytic characterizations. Although computational chemistry has provided an alternative approach to simulate the catalysis process and achieve insights into the reaction pathways, the simulation results would not be conclusive without experimental evidence. Herein, we investigate spatiotemporal electrostatic potential (ESP) distribution surrounding reacting molecules during the catalysis process and suggest its use as a fingerprint to help differentiate and identify active intermediates. Read More

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Lewis acidity of carbon in activated carbonyl group vs. B(C6F5)3 for metal-free catalysis of hydrogenation of carbonyl compounds.

Mojgan Heshmat

Chemphyschem 2021 Mar 3. Epub 2021 Mar 3.

RWTH Aachen, CAT center ITMC, RWTH Aachen University, Worringerweg 2, 52074 Aachen, Germany, 52074, Aachen, GERMANY.

In this work, using DFT calculations, we investigated Lewis acidities of carbon (in activated carbonyl group) in comparison to the BCF in combination with dioxane as the Lewis base (LB) for metal-free catalysis of heterolytic H2 splitting and hydrogenation of carbonyl compounds. We found that in case of carbon as the Lewis acid (LA) the reaction is controlled by frontier molecular orbital interactions between the H2 and LA-LB fragments at shorter distances. The steric effects can be reduced by electrophilic substitutions on the carbonyl carbon. Read More

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Prevention of Na Corrosion and Dendrite Growth for Long-Life Flexible Na-Air Batteries.

ACS Cent Sci 2021 Feb 18;7(2):335-344. Epub 2021 Jan 18.

Tianjin Key Laboratory of Advanced Functional Porous Materials, Institute for New Energy Materials and Low-Carbon Technologies, School of Materials Science and Engineering, Tianjin University of Technology, Binshui Xi dao 391, Xiqing District, 300384 Tianjin, China.

Rechargeable Na-air batteries (NABs) based on abundant Na resources are generating great interest due to their high energy density and low cost. However, Na anode corrosion in ambient air and the growth of abnormal dendrites lead to insufficient cycle performance and safety hazards. Effectively protecting the Na anode from corrosion and inducing the uniform Na plating and stripping are therefore of vital importance for practical application. Read More

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February 2021

The influence of dielectric permittivity of water on the shape of PtNPs synthesized in high-pressure high-temperature microwave reactor.

Sci Rep 2021 Mar 1;11(1):4851. Epub 2021 Mar 1.

School of Chemical Engineering and Advanced Materials, The University of Adelaide, Adelaide, Australia.

In this paper, a novel method for the synthesis of Pt nanoparticles (PtNPs) using a microwave autoclave reactor is proposed. For benchmarking, the obtained results are compared with the traditional, batch method. A novel process window is proposed, which is the application of high-temperature and high-pressure. Read More

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Investigation of the inhibited biotoxicity of heavy metals towards 5- formylcytosine in rice by hydrochar based on photoelectrochemical biosensor.

J Hazard Mater 2021 Feb 18;414:125293. Epub 2021 Feb 18.

College of Chemistry and Material Science, Food Safety Analysis and Test Engineering Technology Research Center of Shandong Province, Shandong Agricultural University, Taian 271018, PR China.

A photoelectrochemical (PEC) biosensor was constructed for 5-formylcytosine (5fC) nucleotide detection based on AgS@WS photoactive material and FeVO catalytic signal quenching. After AgS@WS was modified onto the ITO substrate surface, 5fC recognition reagent of Au@4-amino3hydrazino5mercapto-1,2,4-triazol (Au@AHMT) was further modified through electrostatic adsorption. Afterwards, based on the specific chemical reaction between -NH and -CHO, 5fC can be selectively recognized and captured. Read More

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February 2021

Investigation on the effect of three isoflavones on the fibrillation of hen egg-white lysozyme.

J Mol Recognit 2021 Jun 1;34(6):e2889. Epub 2021 Mar 1.

College of Chemistry, Green Catalysis center, Henan Joint International Research Laboratory of Green Construction of Functional Molecules and their Bioanalytical Applications, Zhengzhou University, Zhengzhou, China.

In this paper, the effects of three isoflavones including daidzein, genistein, and puerarin on fibrillation of hen egg-white lysozyme were investigated by various analytical methods. The results demonstrated that all isoflavones could effectively inhibit the fibrillogenesis of hen egg-white lysozyme and destabilized the preformed fibrils of hen egg-white lysozyme in a dose-dependent manner. To further understand the inhibition mechanism, molecular modeling was carried out. Read More

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Bioactive platinum complex of ligand bearing pyrimidine skeleton: DNA/BSA binding, molecular docking, anticancer, antioxidant and antimicrobial activities.

J Biomol Struct Dyn 2021 Feb 26:1-14. Epub 2021 Feb 26.

Department of Chemistry, V.O. Chidambaram College, Thoothukudi, Tamil Nadu, India.

A new octahedral platinum complex [PtLCl] of Schiff base ligand containing pyrimidine and morpholine skeleton (where, L is 4,6-dichloropyrimidin-5-yl)methylene)-2-morpholinoethanamine) was isolated and characterized by elemental analysis, H-NMR, FTIR, UV-visible and ESI-MS techniques. DNA interaction of isolated compounds with calf thymus (CT-DNA) was explored by UV-vis absorption, fluorescence, cyclic voltametric and viscometric methods. The result shows that prepared compounds can interact with CT-DNA through electrostatic interactions. Read More

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February 2021

Remediation of emerging environmental pollutants: A review based on advances in the uses of eco-friendly biofabricated nanomaterials.

Chemosphere 2021 Jul 15;275:129975. Epub 2021 Feb 15.

Laboratory of Plant Healthcare and Diagnostics, PG Department of Biotechnology and Microbiology, Karnataka University, Dharwad, 580 003, Karnataka, India. Electronic address:

The increased environmental pollutants due to anthropogenic activities are posing an adverse effects and threat on various biotic forms on the planet. Heavy metals and certain organic pollutants by their toxic persistence in the environment are regarded as significant pollutants worldwide. In recent years, pollutants exist in various forms in the environment are difficult to eliminate by traditional technologies due to various drawbacks. Read More

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Discovery of exolytic heparinases and their catalytic mechanism and potential application.

Nat Commun 2021 02 24;12(1):1263. Epub 2021 Feb 24.

National Glycoengineering Research Center and Shandong Key Laboratory of Carbohydrate Chemistry and Glycobiology, Shandong University, Qingdao, China.

Heparinases (Hepases) are critical tools for the studies of highly heterogeneous heparin (HP)/heparan sulfate (HS). However, exolytic heparinases urgently needed for the sequencing of HP/HS chains remain undiscovered. Herein, a type of exolytic heparinases (exoHepases) is identified from the genomes of different bacteria. Read More

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February 2021

Interfacial engineering of BiS/TiCT MXene based on work function for rapid photo-excited bacteria-killing.

Nat Commun 2021 02 22;12(1):1224. Epub 2021 Feb 22.

School of Materials Science & Engineering, The Key Laboratory of Advanced Ceramics and Machining Technology by the Ministry of Education of China, Tianjin University, Tianjin, China.

In view of increasing drug resistance, ecofriendly photoelectrical materials are promising alternatives to antibiotics. Here we design an interfacial Schottky junction of BiS/TiCT resulting from the contact potential difference between TiCT and BiS. The different work functions induce the formation of a local electrophilic/nucleophilic region. Read More

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February 2021

A label-free electrochemiluminescence immunosensor for carbohydrate antigen 153 based on polypyrrole-luminol-AuNPs nanocomposites with bi-catalysis.

Spectrochim Acta A Mol Biomol Spectrosc 2021 May 7;253:119562. Epub 2021 Feb 7.

Xinjiang Key Laboratory of Energy Storage and Photoelectrocatalytic Materials, School of Chemistry and Chemical Engineering, Xinjiang Normal University, Urumqi, Xinjiang 830054, PR China. Electronic address:

Polypyrrole-luminol-AuNPs nanocomposites were prepared and used to develop a sensitive label-free electrochemiluminescence (ECL) immunosensor for carbohydrate antigen 153 (CA153) detection. Firstly, polypyrrole (PPY) nanoparticles were synthesized by a chemical oxidation method using FeCl as an oxidizing agent, then luminol and gold nanoparticles (AuNPs) were combined with PPY nanoparticles through electrostatic interaction to form PPY-luminol-AuNPs nanocomposites. The nanocomposites were characterized by transmission electron microscopy (TEM), UV-Vis absorption spectra, atomic emission spectrometry (AES), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). Read More

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Spherical core-shell alumina support particles for model platinum catalysts.

Nanoscale 2021 Feb;13(7):4221-4232

KU Leuven, Center for Surface Chemistry and Catalysis, Celestijnenlaan 200F, 3001 Leuven, Belgium.

γ- and δ-alumina are popular catalyst support materials. Using a hydrothermal synthesis method starting from aluminum nitrate and urea in diluted solution, spherical core-shell particles with a uniform particle size of about 1 μm were synthesized. Upon calcination at 1000 °C, the particles adopted a core-shell structure with a γ-alumina core and δ-alumina shell as evidenced by 2D and 3D electron microscopy and 27Al magic angle spinning nuclear magnetic resonance spectroscopy. Read More

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February 2021

Enantioselective recognition of tryptophan isomers with molecularly imprinted overoxidized polypyrrole/poly(p-aminobenzene sulfonic acid) modified electrode.

Chirality 2021 04 10;33(4):176-183. Epub 2021 Feb 10.

School of Petrochemical Engineering, Changzhou University, Changzhou, China.

Poly(p-aminobenzene sulfonic acid) (pABSA) was electrodeposited onto the surface of a glassy carbon electrode (GCE), which was then used for the preconcentration of l-tryptophan (l-Trp) due to the electrostatic and π-π interactions between pABSA and l-Trp. Polypyrrole (PPy) was electrodeposited onto the surface of the l-Trp enriched pABSA, and then the l-Trp templates were removed, resulting in molecularly imprinted PPy/pABSA. To avoid the interference from the oxidation peak of PPy on the following electrochemical chiral recognition of Trp isomers, PPy was overoxidized by cyclic voltammetry (CV). Read More

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Sacrificial Synthesis of Supported Ru Single Atoms and Clusters on N-doped Carbon Derived from Covalent Triazine Frameworks: A Charge Modulation Approach.

Adv Sci (Weinh) 2021 Feb 20;8(3):2001493. Epub 2020 Dec 20.

Chemical Sciences Division Oak Ridge National Laboratory Oak Ridge TN 37831 USA.

High-temperature pyrolysis of nitrogen (N)-rich, crystalline porous organic architectures in the presence of a metal precursor is an important chemical process in heterogeneous catalysis for the fabrication of highly porous N-carbon-supported metal catalysts. Herein, covalent triazine framework (CTF) and CTF-I (that is, CTF after charge modulation with iodomethane) are presented as sacrificial templates, for the synthesis of carbon-supported Ru catalysts-Ru-CTF-900 and Ru-CTF-I-900 respectively, following high-temperature pyrolysis at 900 °C under N atmosphere. Predictably, the dispersed Ru on pristine CTF carrier suffered severe sintering of the Ru nanoparticles (NPs) during heat treatment at 900 °C. Read More

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February 2021

Decontamination of bisphenol A and Congo red dye from solution by using CTAB functionalised walnut shell.

Environ Sci Pollut Res Int 2021 Feb 6. Epub 2021 Feb 6.

College of Chemistry, Green Catalysis Center, Zhengzhou University, No 100 of Kexue Road, Zhengzhou, 450001, People's Republic of China.

In this research, the eco-friendly cationic surfactant modified walnut shell (WNS-CTAB) was synthesised to enhance the uptake for bisphenol A (BPA) and Congo red (CR) from aqueous solution. The characterisation of WNS-CTAB was performed using Fourier-transform infrared (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), etc. to know its physiochemical properties. Read More

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February 2021

Electrostatic Interactions Accelerating Water Oxidation Catalysis via Intercatalyst O-O Coupling.

J Am Chem Soc 2021 Feb 4;143(6):2484-2490. Epub 2021 Feb 4.

Department of Theoretical Chemistry & Biology, School of Engineering Sciences in Chemistry Biotechnology and Health, KTH Royal Institute of Technology, 10691 Stockholm, Sweden.

Intercatalyst coupling has been widely applied in the functional mimics for binuclear synergy in natural metal enzymes. Herein, we introduce two facile and effective design strategies, which facilitate the coupling of two catalytic units via electrostatic interactions. The first system is based on a catalyst molecule functionalized with both a positively charged and a negatively charged group in the structure being able to pair with each other in an antiparallel manner arranged by electrostatic interactions. Read More

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February 2021