The high-efficiency coupling of a Ni2+ coordinated/uncoordinated pyridine N-COF self-supporting nanofilm as an asymmetric supercapacitor.

A large-area COFTAPB-BPY film with a pore size of 3.9 nm was prepared on a gas-liquid interface by the virtue of the limiting and guiding functions of sodium dodecylbenzene sulfonate, followed by modification by Ni2+ ions with the reversible redox reaction of Ni(II/III), where Ni2+ was evidently anchored on the N in BPY. The obtained COFTAPB-BPY and Ni-COFTAPB-BPY nanofilms could avoid the inevitable aggregation and stacking of bulk COFTAPB-BPY, which facilitated a high specific capacitance of 0.26 mF cm-2 for the COFTAPB-BPY nanofilm and 0.38 mF cm-2 for the Ni-COFTAPB-BPY nanofilm at 0.001 mA cm-2. Considering the pseudocapacitance and double-layer capacitance traits of Ni-COFTAPB-BPY and COFTAPB-BPY nanofilms, the asymmetric Ni-COFTAPB-BPY//COFTAPB-BPY film supercapacitor was assembled with a symmetric COFTAPB-BPY//COFTAPB-BPY film device as a control. The asymmetric Ni-COFTAPB-BPY//COFTAPB-BPY film supercapacitor could enhance the energy density of 273.9 mW h cm-3 at 14.09 W cm-3 from 85.2 mW h cm-3 at 4.38 W cm-3 for the symmetric COFTAPB-BPY//COFTAPB-BPY film device. This work provides a new perspective on the application of self-supporting COF nanofilms as film asymmetric supercapacitors.

Organocatalytic Asymmetric Vinylogous Michael Addition of Electron-Deficient Aryl Alkane Nucleophiles to Enals.

We report herein a protocol for an organocatalyzed asymmetric vinylogous Michael addition of aryl alkane nucleophiles with enals under base- and additive-free conditions. A series of allylic building blocks were obtained in 60%-93% yield and 88-99% ee with 20 mol % diphenylprolinol silyl ether as catalyst. This protocol has advantages such as excellent chemoselectivity and regioselectivity, good tolerance of functionalities, and simple reaction conditions.

Hexabromocyclododecanes in surface soil-maize system around Baiyangdian Lake in North China: Distribution, enantiomer-specific accumulation, transport, temporal trend and dietary risk.

This study investigated the occurrence of hexabromocyclododecanes (HBCDs) in soil-maize system around Baiyangdian Lake. The total concentration of ΣHBCDs was in the order of industrial area > residential area > marginal area > Fuhe River estuary in soil. γ-HBCD was predominated in soils, roots and stems, while α-HBCD was the main diastereoisomer in leaves and kernels. Concentration of ΣHBCDs and three diastereoisomer concentrations in soils were significantly reduced and remained low level from 2018 to 2019. Selectivity enrichment of (+)α- and (-)γ-HBCD was found in soils, roots, stems and leaves, whereas only (+)ß-HBCD dominated in stems. Most of the total root bioaccumulation factors (ΣRCFs) were less than 1.0, but no significant correlation was showed between translocation factors (TFs) and log Kow. RCFs and TFs of enantiomers suggested (-)ß- and (-)γ-HBCD were easily translocated from soil to roots, while (+)α-, (-)ß- and (-)γ-HBCD tended to translocate from stems to leaves. Estimated daily intake (EDI) and of ΣHBCDs, diastereoisomers and enantiomers were all lower than the threshold value, while the Calculated margins of exposure (MOE) were well above the threshold value, which demonstrate the safe consumption of Maize around Baiyangdian Lake.

Brujavanoids A-U, structurally diverse apotirucallane-type triterpenoids from Brucea javanica and their anti-inflammatory effects.

Extensive phytochemical investigation on the methanol extract of the inflorescences, twigs, and leaves of Brucea javanica led to the isolation and identification of 27 triterpenoids, including 21 previously undescribed ones, named brujavanoids A-U (1-21). Their structures were determined based on comprehensive spectroscopic analysis and single-crystal X-ray diffraction. Of these compounds, brujavanoid A (1) represents the first apotirucallane-type triterpenoid with a novel 19(10 â†’ 9)abeo motif, and brujavanoids B and C (2-3) are the first apotirucallane-type triterpenoids with a rarely occurring 14-hydorxy-15,16-epoxy fragment. All the isolates were evaluated for their anti-inflammatory effect in an LPS-activated RAW264.7 cells model. Furthermore, the most active one, brujavanoid E (5), can suppress the transcriptional expression of typical pro-inflammatory mediators and inhibit the nuclear translocation of NF-κB p65 in the LPS- activated RAW264.7 cells.

Characterization of racemization of chiral pesticides in organic solvents and water.

Eight chiral pesticides, which were selected to cover different pesticide species and origins of chirality, were investigated to explore their chiral stability in organic solvents and water. Profenophos, fenamiphos, quizalofop-ethyl, dichlorprop-methyl (DCPP-methyl) and acetochlor were showed stable under all test conditions. However, significant racemization was observed for malathion, phenthoate and fenpropathrin in methanol, ethanol and water, but not in n-hexane, isopropanol, acetone or methylene chloride. The kinetic parameters (rate constant k and half-life T(1/2)) of the abiotic racemization were calculated through a mathematical model of the first-order reaction. Furthermore, the extent of racemization varied among the solvents and was also affected by temperature dependence. The racemization of malathion, phenthoate and fenpropathrin in water was documented to be pH-dependent and took place more rapidly at pH 7.0 than at pH 5.8. The observed racemization was deduced to occur via a proton exchange process at the chiral center, and the relationship between the abiotic racemization and pesticide structure was further explored. Findings from this study are useful for better understanding enantioselectivity of chiral pesticides in environment and also for proper analysis, formulating or handling of enantiopure products.

Modeling and optimization of phenylalanine ammonia lyase stabilization in recombinant Escherichia coli for the continuous synthesis of l-phenylalanine on the statistical-based experimental designs.

Some approaches for improving recombinant phenylalanine ammonia lyase (PAL) stability in Escherichia coli during the enzymatic methods of l-phenylalanine (l-Phe) production were developed following preliminary studies by means of statistical-based experiment designs (response surface method). The traditional non-statistical technology was used to screen four critical factors for PAL stability during the bioconversion process, viz., glycerin, sucrose, 1,4-dithiothreitol (DTT), and MgSO(4). The central composite design (CCD) was applied to optimize the combined effect of critical factors for recombinant PAL stability and understand the relationship between the factors and PAL stability. The optimum values for testing variables were 13.04 mM glycerin, 1.87 mM sucrose, 4.09 mM DTT, and 69 mM Mg(2+). A second-order model equation was suggested and then validated experimentally. The model adequacy was very satisfactory because the coefficient of determination was 0.88. The maximum PAL activity was retained as 67.73 units/g after three successive cycles of bioconversion. In comparison to initial PAL activity, the loss of PAL activity was only 22%. PAL activity was enhanced about 23% in comparison to the control (without any stabilizer additives). PAL stability was significantly improved during successive bioconversion. The results obtained here verified the effectiveness of the applied methodology and may be helpful for l-Phe production on an industrial scale.

1-Phenyl-1-[(1-phenyl-ethyl)sulfonyl-methyl-sulfon-yl]ethane.

There are two mol-ecules in the asymmetric unit of the title compound, C(17)H(20)O(4)S(2). There are slight differences in the twist of the two rings relative to the S-C-S chain [dihedral angles of 48.41 (18) and 87.58 (16)° in the first mol-ecule and 45.98 (18) and 87.02 (18)° in the second] and the difference in the C-S-C-S torsion angles [176.68 (17) and -77.6 (2)° for the two independent mol-ecules].

(4RS)-3-Benzyl 5-methyl 2,6-dimethyl-4-(4-nitro-phen-yl)-1,4-dihydro-pyridine-3,5-dicarboxyl-ate.

In the title compound, C(23)H(22)N(2)O(6), the crystal packing is stabilized by inter-molecular N-H⋯O hydrogen bonds, which link the mol-ecules into chains running parallel to the c axis. Inter-molecular C-H⋯O hydrogen bonds are also present in the structure.