scholarly journals Rational Design for Enhanced Acyltransferase Activity in Water Catalyzed by the Pyrobaculum calidifontis VA1 Esterase

2021 ◽  
Vol 9 (8) ◽  
pp. 1790
Author(s):  
Amanda Staudt ◽  
Henrik Terholsen ◽  
Jasmin Kaur ◽  
Henrik Müller ◽  
Simon P. Godehard ◽  
...  
Keyword(s):  
Organic Solvents ◽  
Rational Design ◽  
Bulk Water ◽  
Acyl Transfer ◽  
Acyl Donor ◽  
Acyltransferase Activity ◽  
Pyrobaculum Calidifontis ◽  
Synthetic Strategy ◽  
Highly Active ◽  
Acyl Transfer Activity

Biocatalytic transesterification is commonly carried out employing lipases in anhydrous organic solvents since hydrolases usually prefer hydrolysis over acyl transfer in bulk water. However, some promiscuous acyltransferases can catalyze acylation in an aqueous solution. In this study, a rational design was performed to enhance the acyltransferase selectivity and substrate scope of the Pyrobaculum calidifontis VA1 esterase (PestE). PestE wild type and variants were applied for the acylation of monoterpene alcohols. The mutant PestE_I208A is selective for (–)-menthyl acetate (E-Value = 55). Highly active acyltransferases were designed, allowing for complete conversion of (–)-citronellol to citronellyl acetate. Additionally, carvacrol was acetylated but with lower conversions. To the best of our knowledge, this is the first example of the biocatalytic acylation of a phenolic alcohol in bulk water. In addition, a high citronellol conversion of 92% was achieved with the more environmentally friendly and inexpensive acyl donor ethyl acetate using PestE_N288F as a catalyst. PestE_N288F exhibits good acyl transfer activity in an aqueous medium and low hydrolysis activity at the same time. Thus, our study demonstrates an alternative synthetic strategy for acylation of compounds without organic solvents.

scholarly journals Facet-Dependent Reactivity of Ceria Nanoparticles Exemplified by CeO2-Based Transition Metal Catalysts: A Critical Review

Catalysts ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 452
Author(s):  
Michalis Konsolakis ◽  
Maria Lykaki
Keyword(s):  
Transition Metal ◽  
Co Oxidation ◽  
Critical Review ◽  
Rational Design ◽  
Metal Catalysts ◽  
Co2 Hydrogenation ◽  
Transition Metal Catalysts ◽  
Fine Tuning ◽  
Ceria Nanoparticles ◽  
Highly Active

The rational design and fabrication of highly-active and cost-efficient catalytic materials constitutes the main research pillar in catalysis field. In this context, the fine-tuning of size and shape at the nanometer scale can exert an intense impact not only on the inherent reactivity of catalyst’s counterparts but also on their interfacial interactions; it can also opening up new horizons for the development of highly active and robust materials. The present critical review, focusing mainly on our recent advances on the topic, aims to highlight the pivotal role of shape engineering in catalysis, exemplified by noble metal-free, CeO2-based transition metal catalysts (TMs/CeO2). The underlying mechanism of facet-dependent reactivity is initially discussed. The main implications of ceria nanoparticles’ shape engineering (rods, cubes, and polyhedra) in catalysis are next discussed, on the ground of some of the most pertinent heterogeneous reactions, such as CO2 hydrogenation, CO oxidation, and N2O decomposition. It is clearly revealed that shape functionalization can remarkably affect the intrinsic features and in turn the reactivity of ceria nanoparticles. More importantly, by combining ceria nanoparticles (CeO2 NPs) of specific architecture with various transition metals (e.g., Cu, Fe, Co, and Ni) remarkably active multifunctional composites can be obtained due mainly to the synergistic metalceria interactions. From the practical point of view, novel catalyst formulations with similar or even superior reactivity to that of noble metals can be obtained by co-adjusting the shape and composition of mixed oxides, such as Cu/ceria nanorods for CO oxidation and Ni/ceria nanorods for CO2 hydrogenation. The conclusions derived could provide the design principles of earth-abundant metal oxide catalysts for various real-life environmental and energy applications.

Electrochemical oxidation of 5-hydroxymethylfurfural on ternary metal-organic frameworks nanoarrays: enhancement from electronic structure modulation

2021 ◽  
Author(s):  
Xiaojue Bai ◽  
Wenxiu He ◽  
Xingyu Lu ◽  
Yu Fu ◽  
Wei Qi
Keyword(s):  
Electronic Structure ◽  
Carboxylic Acid ◽  
Electrochemical Oxidation ◽  
Rational Design ◽  
Metal Organic Frameworks ◽  
Highly Active ◽  
Ternary Metal ◽  
Metal Organic ◽  
Structure Modulation

The rational design and exploitation of highly active and stable catalysts for the electrochemical oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) to valuable chemical 2,5-furandi-carboxylic acid (FDCA), is of great significance. Herein,...

scholarly journals The role of side chains in the interaction of new antitumor pyrimidoacridinetriones with DNA: molecular dynamics simulations.

2000 ◽  
Vol 47 (1) ◽  
pp. 47-57 ◽  
Author(s):  
J Mazerski ◽  
I Antonini ◽  
S Martelli
Keyword(s):  
Molecular Dynamics ◽  
Rational Design ◽  
Md Simulations ◽  
Ring System ◽  
Side Chain ◽  
Side Chains ◽  
Intercalation Complex ◽  
Highly Active ◽  
Simulation Techniques ◽  
Dynamics Simulations

Pyrimidoacridinetriones (PATs) are a new group of highly active antitumor compounds. It seems reasonable to assume that, like for some other acridine derivatives, intercalation into DNA is a necessary, however not a sufficient condition for antitumor activity of these compounds. Rational design of new compounds of this chemotype requires knowledge about the structure of the intercalation complex, as well as about interactions responsible for its stability. Computer simulation techniques such as molecular dynamics (MD) may provide valuable information about these problems. The results of MD simulations performed for three rationally selected PATs are presented in this paper. The compounds differ in the number and position of side chains. Each of the compounds was simulated in two systems: i) in water, and ii) in the intercalation complex with the dodecamer duplex d(GCGCGCGCGCGC)2. The orientation of the side chain in relation to the ring system is determined by the position of its attachment. Orientation of the ring system inside the intercalation cavity depends on the number and position of side chain(s). The conformations of the side chain(s) of all PATs studied in the intercalation complex were found to be very similar to those observed in water.

scholarly journals Dinuclear thiazolylidene copper complex as highly active catalyst for azid–alkyne cycloadditions

2016 ◽  
Vol 12 ◽  
pp. 1566-1572 ◽  
Author(s):  
Anne L Schöffler ◽  
Ata Makarem ◽  
Frank Rominger ◽  
Bernd F Straub
Keyword(s):  
Acetic Acid ◽  
Organic Solvents ◽  
Copper Complex ◽  
Room Temperature ◽  
Active Catalyst ◽  
Catalyst Design ◽  
Ancillary Ligand ◽  
Click Reactions ◽  
Highly Active ◽  
Cost Efficient

A dinuclear N-heterocyclic carbene (NHC) copper complex efficiently catalyzes azide–alkyne cycloaddition (CuAAC) “click” reactions. The ancillary ligand comprises two 4,5-dimethyl-1,3-thiazol-2-ylidene units and an ethylene linker. The three-step preparation of the complex from commercially available starting compounds is more straightforward and cost-efficient than that of the previously described 1,2,4-triazol-5-ylidene derivatives. Kinetic experiments revealed its high catalytic CuAAC activity in organic solvents at room temperature. The activity increases upon addition of acetic acid, particularly for more acidic alkyne substrates. The modular catalyst design renders possible the exchange of N-heterocyclic carbene, linker, sacrificial ligand, and counter ion.

Effective Monofunctional Azaphthalocyanine Photosensitizers for Photodynamic Therapy

2009 ◽  
Vol 62 (5) ◽  
pp. 425 ◽  
Author(s):  
Petr Zimcik ◽  
Miroslav Miletin ◽  
Veronika Novakova ◽  
Kamil Kopecky ◽  
Marcela Nejedla ◽  
...  
Keyword(s):  
Photodynamic Therapy ◽  
Carboxy Group ◽  
Rational Design ◽  
Photophysical Properties ◽  
Active Part ◽  
Third Generation ◽  
Highly Active ◽  
Low Degree ◽  
Band Absorption ◽  
Group B

In this work we present a rational design of the active part of third generation photosensitizers for photodynamic therapy based on phthalocyanine and an azaphthalocyanine core. The preferred zinc complexes of the AAAB type that contain bulky tert-butylsulfanyl substituents (A) and one carboxy group (B) have been synthesized by statistical condensation and fully characterized. The tetramerization was performed using magnesium(ii) butoxide followed by demetalation and insertion of ZnII. Compound 1 synthesized from 4,5-bis(tert-butylsulfanyl)phthalonitrile (A) and 2,3-dicyanoquinoxaline-6-carboxylic acid (B) exerted very promising photophysical properties (Q-band absorption at 726 nm, ϵ = 140000 M–1 cm–1), which allowed strong absorption of light at long wavelengths where the penetration of the light through human tissues is deeper. The very high singlet oxygen quantum yield of 1 (ΦΔ = 0.80) assures efficient photosensitization. As a result of bulky peripheral substituents, compound 1 shows good solubility in organic solvents with a low degree of aggregation, which makes it potentially viable for non-complicated modification. One carboxy group in the final structure of 1 allows simple binding to possible carriers. This compound is suitable for binding to targeting moieties to form the highly active part of a third-generation photosensitizer.

scholarly journals Reaction: Rational Design of Highly Active Photocatalysts for CO2 Conversion

Chem ◽  
2020 ◽  
Vol 6 (5) ◽  
pp. 1039-1040 ◽  
Author(s):  
Yang Xia ◽  
Jiaguo Yu
Keyword(s):  
Rational Design ◽  
Co2 Conversion ◽  
Highly Active

scholarly journals Transition Metal Carbide Core/Shell Nanoparticles by Ultra-Short Laser Ablation in Liquid

Nanomaterials ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 145 ◽  
Author(s):  
Angela De Bonis ◽  
Mariangela Curcio ◽  
Antonio Santagata ◽  
Agostino Galasso ◽  
Roberto Teghil
Keyword(s):  
Laser Ablation ◽  
Transition Metal ◽  
Organic Solvents ◽  
Transition Metal Carbide ◽  
Metal Carbide ◽  
Laser Ablation In Liquid ◽  
Shell Nanoparticles ◽  
Synthetic Strategy ◽  
Molybdenum Carbides ◽  
Wide Range

Transition metal carbide nanoparticles are a class of technological interesting materials with a wide range of applications. Among metal carbides, tantalum carbides have good compatibility with the biological environment while molybdenum carbides are used as catalyst in electrochemical reactions. Laser ablation of bulk transition metal targets in some liquids is here reported and laser ablation in organic solvents is used as simple synthetic strategy for the production of carbide nanostructures. Herein, the nanoparticles produced by ultra-short laser ablation of tantalum and molybdenum in water, acetone, ethanol and toluene have been characterized by TEM, XRD and XPS analysis. The combined effect of metal and solvent chemical and physical properties on the composition of the nanomaterials obtained has been pointed out. In particular, the different reactivity of Ta and Mo with respect to oxidizing species determines the composition of particles obtained in water, on the other hand the organic solvents decomposition allows to obtain transition metal carbide (TMC) nanoparticles. The observed carbonaceous shell formed on TMC allows to protect the particle’s carbidic core and to improve and tailor the applications of these nanomaterials.

scholarly journals Enzymatic synthesis and application of fatty acid ascorbyl esters

2013 ◽  
Vol 67 (2) ◽  
pp. 239-247 ◽  
Author(s):  
Marija Stojanovic ◽  
Milica Carevic ◽  
Mladen Mihailovic ◽  
Zorica Knezevic-Jugovic ◽  
Slobodan Petrovic ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Vitamin C ◽  
Organic Solvents ◽  
Molecular Sieves ◽  
Reaction Medium ◽  
Log P ◽  
Acyl Donor ◽  
Vinyl Esters ◽  
Ascorbyl Esters ◽  
Acyl Donors

Fatty acid ascorbyl esters are liposoluble substances that possess good antioxidative properties. These compounds could be synthesized by using various acyl donors for acylation of vitamin C in reaction catalyzed by chemical means or lipases. Enzymatic process is preferred since it is regioselective, performed under mild reaction conditions, with the obtained product being environmentally friendly. Polar organic solvents, ionic liquids, and supercritical fluids has been successfully used as a reaction medium, since commonly used solvents with high Log P values are inapplicable due to ascorbic acid high polarity. Acylation of vitamin C using fatty acids, their methyl-, ethyl-, and vinyl esters, as well as triglycerides has been performed, whereas application of the activated acyl donors enabled higher molar conversions. In each case, majority of authors reported that using excessive amount of the acyl donor had positive effect on yield of product. Furthermore, several strategies have been employed for shifting the equilibrium towards the product by water content control. These include adjusting the initial water activity by pre-equilibration of reaction mixture, enzyme preparation with water vapor of saturated salt solutions, and the removal of formed water by the addition of molecular sieves or salt hydrate pairs. The aim of this article is to provide a brief overview of the procedures described so far for the lipase-catalyzed synthesis of fatty acid ascorbyl esters with emphasis on the potential application in food, cosmetics, and pharmaceutics. Furthermore, it has been pointed out that the main obstacles for process commercialization are long reaction times, lack of adequate purification methods, and high costs of lipases. Thus, future challenges in this area are testing new catalysts, developing continuous processes for esters production, finding cheaper acyl donors and reaction mediums, as well as identifying standard procedures for purification of products which will not require consumption of large amounts of non-biocompatible organic solvents.

Rational design of ordered Pd–Pb nanocubes as highly active, selective and durable catalysts for solvent-free benzyl alcohol oxidation

Nanoscale ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 5145-5150 ◽  
Author(s):  
Chongyang Tang ◽  
Nan Zhang ◽  
Qi Shao ◽  
Xiaoqing Huang ◽  
Xiangheng Xiao
Keyword(s):  
Benzyl Alcohol ◽  
Rational Design ◽  
Alcohol Oxidation ◽  
Solvent Free ◽  
Benzyl Alcohol Oxidation ◽  
Highly Active ◽  
Better Than

Ordered Pd–Pb nanocubes (NCs) were adopted as efficient heterocatalysts for the selective benzyl alcohol oxidation. Due to the ordered phase and well-defined surface, the Pd–Pb NCs can achieve superior activity and selectivity, better than those of other catalysts as we prepared.

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