Using Small Molecules to Enhance P450 OleT Enzyme Activity in Situ.

Cytochrome P450 OleT is a fatty acid decarboxylase that catalyzes the production of olefins with biofuel and synthetic applications. However, the relatively sluggish catalytic efficiency of the enzyme limits its applications. Here, we report the application of a novel class of benzene containing small molecules to improve the OleT activity. The UV-Vis spectroscopy study and molecular docking results confirmed the high proximity of the small molecules to the heme group of OleT. Up to 6-fold increase of product yield has been achieved in the small molecule-modulated enzymatic reactions. Our work thus sheds the light to the application of small molecules to increase the OleT catalytic efficiency, which could be potentially used for future olefin productions.

Visible-Light-Induced Oxidative C-H Functionalization of Unreactive Cycloalkanes, Alcohols, and Ethers with Alkynylphosphine Oxides into Benzo[b]phosphole Oxides under Photocatalyst-, Metal-, and Base-Free Conditions.

We developed the radical cyclization/addition of alkynylphosphine oxides with easily available cycloalkanes, alcohols, and ethers using a visible-light and environmentally friendly synthetic strategy in the absence of photocatalyst at room temperature. This mild and metal- and base-free reaction provided a structurally varied set of significant benzo[b]phosphole oxides through sequential C-H functionalization in an atom-economical manner.

Azobisisobutyronitrile-Initiated Oxidative C-H Functionalization of Simple Alcohols with Diaryl(arylethynyl)phosphine Oxides: A Metal-Free Approach toward Hydroxymethyl Benzo[b]phosphole Oxides and 6H-Indeno[2,1-b]phosphindole 5-Oxide Derivatives.

The first metal-free and facile radical addition/cyclization of simple alcohols with diaryl(arylethynyl)phosphine oxides has been described with azobisisobutyronitrile as a radical initiator, affording an efficient and one-pot procedure to access a new class of hydroxymethyl benzo[b]phosphole oxides and 6H-indeno[2,1-b]phosphindole 5-oxides for potential application in organic materials via sequential C(sp3)-H/C(sp2)-H functionalization. The method employs easily accessible starting materials and is endowed with high regioselectivity and broad functional-group tolerance.

Two-step pyrolysis biochar derived from agro-waste for antibiotics removal: Mechanisms and stability.

This study used acetone washing biochar (BCA) and nitric-acid washing biochar (BCN) derived from bagasse to remove sulfamethoxazole (SMX) and tetracycline (TC) in water. Higher specific surface area (1119.53 m2 g-1) and graphitization degree can significantly improve decontamination efficacy, of which BCN has the highest SMX and TC sorption capacities (274.63 mg g-1 and 353.85 mg g-1). The kinetics, isotherms and characterization analysis indicated O-containing functional group complexation and π-π interaction were dominant mechanisms in the adsorption process. Adsorption stability experiment showed that BCA has better stability with the coexistence of anions and cations. Besides, the enhancement and competitive adsorption from the interaction between soluble organic matter and TC could facilitate TC decontamination. Therefore, bagasse biochar derived from agro-waste has a promising potential for antibiotic contaminants removal from multi-interference conditions and promotes the recycling of waste, thereby achieving harmony between materials and the ecological environment.

Influence of a Novel Mixed Dialkyl Oxalate on the Combustion and Emission Characteristics of a Diesel Engine.

Oxygen-containing alternative fuels have excellent potential to improve diesel fuel economy and reduce particulate matter (PM) emissions. In this study, a novel mixed dialkyl oxalate (mDAO) as an additive was applied to substitute conventional diesel to investigate the effects of mDAO on the combustion and emission characteristics of a high-pressure common-rail diesel engine. The research conducted suggested that the peak pressure rise rate in the main injection stage and the peak in-cylinder pressure presented the rising tendency with the increased mass fraction of mDAO at most test conditions. With the addition of mDAO, the in-cylinder temperature (T) and brake thermal efficiency (BTE) were higher than that of pure diesel. When the mass fraction of mDAO in the mDAO/diesel blend was 30%, the improvement of BTE was most obvious. The ignition delay was prolonged as the mass fraction of mDAO was increased due to the lower cetane number of the mDAO. In addition, adding mDAO into diesel had an effective impact on the reduction of PM emissions, while the nitrogen oxide (NO x ) emissions deteriorated. These results indicate that mDAO is a great potential diesel alternative fuel.

Spectroscopic studies of the interaction between phosphorus heterocycles and cytochrome P450.

P450 fatty acid decarboxylase OleT from Staphylococcus aureus (OleTSA) is a novel cytochrome P450 enzyme that catalyzes the oxidative decarboxylation of fatty acids to yield primarily terminal alkenes and CO2 or minor α- and ß-hydroxylated fatty acids as side-products. In this work, the interactions between a series of cycloalkyl phosphorus heterocycles (CPHs) and OleTSA were investigated in detail by fluorescence titration experiment, ultraviolet-visible (UV-vis) and 31P NMR spectroscopies. Fluorescence titration experiment results clearly showed that a dynamic quenching occurred when CPH-6, a representative CPHs, interacted with OleTSA with a binding constant value of 15.2 × 104 M-1 at 293 K. The thermodynamic parameters (ΔH, ΔS and ΔG) showed that the hydrogen bond and van der Waals force played major roles in the interaction between OleTSA and CPHs. The UV-vis and 31P NMR studies indicated the penetration of CPH-6 into the interior environment of OleTSA, which greatly affects the enzymatic activity of OleTSA. Therefore, our study revealed an effective way to use phosphorus heterocyclic compounds to modulate the activity of cytochrome P450 enzymes.

Voltage-responsive vesicles based on orthogonal assembly of two homopolymers.

Two end-decorated homopolymers, poly(styrene)-beta-cyclodextrin (PS-beta-CD) and poly(ethylene oxide)-ferrocene (PEO-Fc), can orthogonally self-assemble into a supramolecular diblock copolymer (PS-beta-CD/PEO-Fc) in aqueous solutions based on the terminal host-guest interactions. These assemblies can further form supramolecular vesicles, and their assembly and disassembly behaviors can be reversibly switched by voltage through the reversible association and disassociation of the middle supramolecular connection. The vesicles possess an unprecedented property that their assembly or disassembly speed can be controlled by the applied voltage strength. Luminescence spectroscopy demonstrates that the vesicles act as nanocapsules carrying molecules within their hollow cavities and that the external voltage strength accurately regulates the drug release time.

Enhanced P450 fatty acid decarboxylase catalysis by glucose oxidase coupling and co-assembly for biofuel generation.

Cytochrome P450 OleT is a fatty acid decarboxylase that uses hydrogen peroxide (H2O2) to catalyze the production of terminal alkenes, which are industrially important chemicals with biofuel and synthetic applications. Despite its requirement for large turnover levels, high concentrations of H2O2 may cause heme group degradation, diminishing enzymatic activity and limiting broad application for synthesis. Here, we report an artificial enzyme cascade composed of glucose oxidase (GOx) and OleTSA from Staphylococcus aureus for efficient terminal alkene production. By adjusting the ratio of GOx to OleTSA, the GOx-based tandem catalysis shows significantly improved product yield compared to the H2O2 injection method. Moreover, the co-assembly of the GOx/OleTSA enzymes with a polymer, forming polymer-dual enzymes nanoparticles, displays improved activity compared to the free enzyme. This dual strategy provides a simple and efficient system to transform a naturally abundant feedstock to industrially important chemicals.

Palladium-Catalyzed Addition/Cyclization of (2-Hydroxyaryl)boronic Acids with Alkynylphosphonates: Access to Phosphacoumarins.

A facile palladium-catalyzed addition/cyclization of (2-hydroxyaryl)boronic acids with alkynylphosphonates has been developed, providing an effective strategy to construct a series of valuable phosphacoumarins. This methodology features excellent regioselectivity and broad substrate tolerance.

Correction: Enabling nanopore technology for sensing individual amino acids by a derivatization strategy.

Correction for 'Enabling nanopore technology for sensing individual amino acids by a derivatization strategy' by Xiaojun Wei et al., J. Mater. Chem. B, 2020, 8, 6792-6797, DOI: 10.1039/D0TB00895H.

Enabling nanopore technology for sensing individual amino acids by a derivatization strategy.

Nanopore technology holds remarkable promise for sequencing proteins and peptides. To achieve this, it is necessary to establish a characteristic profile for each individual amino acid through the statistical description of its translocation process. However, the subtle molecular differences among all twenty amino acids along with their unpredictable conformational changes at the nanopore sensing region result in very low distinguishability. Here we report the electrical sensing of individual amino acids using an α-hemolysin nanopore based on a derivatization strategy. Using derivatized amino acids as detection surrogates not only prolongs their interactions with the sensing region, but also improves their conformational variation. Furthermore, we show that distinct characteristics including current blockades and dwell times can be observed among all three classes of amino acids after 2,3-naphthalenedicarboxaldehyde (NDA)- and 2-naphthylisothiocyanate (NITC)-derivatization, respectively. These observable characteristics were applied towards the identification and differentiation of 9 of the 20 natural amino acids using their NITC derivatives. The method demonstrated herein will pave the way for the identification of all amino acids and further protein and peptide sequencing.

N-Terminal Derivatization-Assisted Identification of Individual Amino Acids Using a Biological Nanopore Sensor.

Nanopore technology has been employed as a powerful tool for DNA sequencing and analysis. To extend this method to peptide sequencing, a necessary step is to profile individual amino acids (AAs) through their nanopore stochastic signals, which remains a great challenge because of the low signal-to-noise ratio and unpredictable conformational changes of AAs during their translocation through nanopores. We showed that the combination of an N-terminal derivatization strategy of AAs with nanopore technology could lead to effective in situ differentiation of AAs. Four different derivatization reactions have been tested with five selected AAs: Ala, Phe, Tyr, His, and Asp. Using an α-hemolysin nanopore, we demonstrated the feasibility of derivatization-assisted identification of AAs regardless of their charge composition and polarity. The method was further applied to discriminate each individual AA in testing data sets using their established nanopore profiles from training data sets. We envision that this proof-of-concept study will not only pave a way for identification of individual AAs but also lead to future applications in protein/peptide sequencing using the nanopore technology.

Cellulose-based dual graft molecular brushes as potential drug nanocarriers: stimulus-responsive micelles, self-assembled phase transition behavior, and tunable crystalline morphologies.

Well-defined cellulose-based dual graft molecular brushes, composed of ethyl cellulose-graft-poly(N,N-dimethylaminoethyl methacrylate)-graft-poly(epsilon-caprolactone) (EC-g-PDMAEMA-g-PCL), have been prepared by ring-opening polymerization (ROP) and atom transfer radical polymerization (ATRP). Unlike other brush copolymers, the new molecular brushes show some unique physicochemical properties and multifunction due to their unique topological structures. These biocompatible copolymers self-assembled to micelles in aqueous solution. Upon pH change, the single micelles further assembled into micellar aggregates. As a result, the micelles in aqueous media could act as excellent drug nanocarriers for controlled drug release. The crystallinity and crystal morphology of the copolymers can be controlled to a certain extent by varying the length of the side chains, which may exert strong spacial restriction and, hence, affect the crystal structures.

Copolymer logical switches adjusted through core-shell micelles: from temperature response to fluorescence response.

Aqueous solution of micelles prepared from novel PS-b-PNIPAM with fluorescent group CEA at the junction between two blocks displays logical responsive switches on temperature and fluorescence; at lower temperature, stretching of PNIPAM chains causes high mobility of CEA leading to formation of more excimer species; at higher temperature, shrinking of PNIPAM chains isolates the fluorescent groups between the core and shell, resulting in fewer excimer species.

Copper-Catalyzed Direct Oxidative C-H Functionalization of Unactivated Cycloalkanes into Cycloalkyl Benzo[ b]phosphole Oxides.

The first simple and efficient Cu-catalyzed radical addition/cyclization of various unactivated cycloalkanes with diaryl(arylethynyl)-phosphine oxides has been developed, providing a general, one-step approach to construct a new class of important benzo[ b]phosphole oxides via sequential C-H functionalization along with two new C-C bond formations.

Facile synthesis of α-alkoxyl amides via scandium-catalyzed oxidative reaction between ynamides and alcohols.

A novel and efficient scandium-catalyzed oxidative reaction between ynamides and alcohols for the facile synthesis of various α-alkoxyl amides is reported in this paper. The reaction avoids the need for the use of α-diazo carbonyls which are unstable and may cause some safety concerns. Instead, by using alkynes as the starting materials, this protocol features readily available substrates, compatibility with a broad range of functional groups, simple procedure, mild reaction conditions, and high chemoselectivity.

ZrOCl2 x 8H2O: an efficient, cheap and reusable catalyst for the esterification of acrylic acid and other carboxylic acids with equimolar amounts of alcohols.

Esterifications of carboxylic acids with equimolar amount of alcohols could be efficiently catalyzed by ZrOCl(2) x 8H(2)O. Acrylate esters were obtained in good yields under solvent-free conditions at ambient temperature. The esterification of other carboxylic acids with alcohols also proceeded at ambient temperature or at 50 oC to afford esters in high yields. If the esterification was performed in toluene under azeotropic reflux conditions to remove water, both the catalytic activity of ZrOCl(2) x 8H(2)O and the rate of esterification could be increased greatly. Furthermore, in the present catalytic system, the esters could be easily separated from the reaction mixtures and the catalyst could be easily recovered and reused.

Fast liquefaction of bamboo shoot shell with liquid-phase microplasma assisted technology.

In this study, liquid-phase microplasma technology (LPMPT) was employed to facilitate the liquefaction of bamboo shoot shell (BSS) in polyethylene glycol 400 (PEG 400) and ethylene glycol (EG) mixture. Effects of liquefaction conditions such as liquefaction time, catalyst percentage, solvent/BSS mass ratio, PEG/EG volume ratio on liquefaction were investigated experimentally. The results showed that the introduction of LPMPT significantly shortened the liquefaction time to 3min without extra heating. The liquefaction yield reached 96.73% under the optimal conditions. The formation of massive reactive species and instantaneous heat accumulation both contributed to the rapid liquefaction of BSS. Thus, LPMPT could be considered as a simple and efficient method for the assistance of biomass fast liquefaction.