Development of Microtiter Plate Culture Method for Rapid Screening of ε-Poly-L-Lysine-Producing Strains

ε-Poly-l-lysine (ε-PL) produced by Streptomyces albulus possesses a broad spectrum of antimicrobial activity and is widely used as a food preservative. To extensively screen ε-PL-overproducing strain, we developed an integrated high-throughput screening assay using ribosome engineering technology. The production protocol was scaled down to 24- and 48-deep-well microtiter plates (MTPs). The microplate reader assay was used to monitor ε-PL production. A good correlation was observed between the fermentation results obtained in both 24-(48)-deep-well MTPs and conventional Erlenmeyer flasks. Using this protocol, the production of ε-PL in an entire MTP was determined in <5 min without compromising on accuracy. The high-yielding strain selected through this protocol was also tested in Erlenmeyer flasks. The result showed that the ε-PL production of the high-yielding mutants was nearly 45% higher than that of the parent stain. Thus, development of this protocol is expected to accelerate the selection of ε-PL-overproducing strains.     

Facile synthesis of novel [1,3]oxazino[2,3-c][1,2,4] thiadiazin-12-one derivatives

Several novel fused heterocyclic systems which have rings containing N/O or N/S have been synthesized through a facile one-pot method by the treatment of substituted 2-(benzo[d]thiazol-2-yl)phenol and cyanogen bromide in THF and NEt₃. This one-pot method contains tough ring-opening of thiazole, special intermolecular rearrangement and ring-closing reactions. The newly synthesized compounds were characterized by HR-MS, ¹H-NMR, ¹³C-NMR spectral data and DFT calculation analysis. 2a was also determined by X-ray crystallographic analysis.     

Inhibition effect of pomelo peel extract for N80 steel in 3.5% NaCl saturated with CO2 solution

Research on Chemical Intermediates - Pomelo peel extract (PPE) has been evaluated as a corrosion inhibitor for N80 steel in 3.5% NaCl saturated with CO2 solution using weight loss measurements,...     

Physical properties and thermal behavior of reconstituted tobacco sheet with precipitated calcium carbonate added in the coating process

Addition of precipitated calcium carbonate (PCC) to cellulosic products can reduce production costs and modify their physical properties. This study investigated the effects of adding PCC on the properties of reconstituted tobacco sheet (RTS), a cellulosic product. Scanning electron microscopy (SEM) analysis showed that adding PCC to the coating could modify the surface microstructure of RTS. With increasing PCC addition, the strength and tar release per cigarette of RTS decreased. However, the filling capacity, bulk, and CO release content in the mainstream smoke reached optimal values when the proportion of PCC in the coating was 8%. Thermogravimetry (TG) and differential thermogravimetry (DTG) analysis indicated that the main thermal pyrolysis stage occurred in the range of 200–400 °C, similar to cellulosic components. The Coats–Redfern equation was used to analyze the thermal pyrolysis mechanism. The fitting results showed that, in the range of 200–280 °C, the best fit model for RTS with 4 or 8% PCC was diffusion-controlled reaction (D1) with fitting correlation coefficient (r ²) of 0.9630 and 0.9576, respectively. Meanwhile, in the range of 280–400 °C, the most reliable fitting model for RTS with 4% PCC was chemical reaction (F2) with r ² = 0.9681. One reaction model could not describe the thermal pyrolysis of RTS with 12% PCC in the main decomposition stage. The thermal kinetic parameters suggested that addition of PCC to RTS coatings could modify the thermal pyrolysis mechanism, but did not change the peak temperatures in the main thermal decomposition stage. This study demonstrates that addition of PCC to RTS coating is a promising method to improve its quality.     

苯酰亚胺结构对PET阻燃抗熔滴及抑烟的贡献

通过本体聚合方法合成了一系列侧链含苯酰亚胺结构的聚对苯二甲酸乙二酯(PET)共聚酯.研究发现,苯酰亚胺单元的引入不仅提高了共聚酯的玻璃化转变温度(T_g)和高温成炭性,并且大大降低了共聚酯高温下的热分解速率.随着苯酰亚胺含量的增加,共聚酯表现出更高的氧指数(LOI)值和更好的阻燃抗熔滴效果.锥形量热测试结果表明,苯酰亚胺结构的引入可以有效地降低共聚酯的峰值热释放速率(p-HRR)、峰值烟释放速率(p-RSR)和总烟释放量(TSR).通过对纯PET和共聚酯燃烧测试后残炭的结构和形貌分析,发现苯酰亚胺结构有助于共聚酯形成石墨化程度更高的致密炭层,这些炭层起到隔热隔氧和抑制有机可燃烟气挥发的作用,在不引入传统阻燃剂的情况下,赋予共聚酯很好的本征阻燃性及抑烟性.     

A facile synthesis of novel endo-selective polycyclic spiropyrrolidine oxindoles via 1,3-dipolar cycloaddition of α,γ-dialkylallenoate esters

Novel polycyclic spiropyrrolidine oxindoles that bear two vicinal quaternary centers and an exocyclic CC double bond have been synthesized by a three-component reaction involving α,γ-dialkylallenoate esters, isatin derivatives and amino acids, by way of an endo-selective 1,3-dipolar cycloaddition. These reactions proceed in high yields and diastereoselectivities. The structures and relative stereochemistry of products were confirmed by NMR, HRMS and X-ray crystallography.     

Self-Assembly of Alkylammonium Chains on Montmorillonite: Effect of Interlayer Cations,CEC, and Chain Length

Recently, polymeric materials have been filled with synthetic or natural inorganic compounds in order to improve their properties. Especially, polymer clay nanocomposites have attracted both academic and industrial attention. Currently, the structure and physical phenomena of organoclays at molecular level are difficultly explained by existing experimental techniques. In this work, molecular dynamics (MD) simulation was executed using the CLAYFF and CHARMM force fields to evaluate the structural properties of organoclay such as basal spacing, interlayer density, energy and the arrangement of alkyl chains in the interlayer spacing. Our results are in good agreement with available experimental or other simulation data. The effects of interlayer cations (Na⁺, K⁺, Ca²⁺), the cation exchange capacity, and the alkyl chain length on the basal spacing and the structural properties are estimated. These simulations are expected to presage the microstructure of organo-montmorillonite and lead relevant engineering applications.     

Efficient copper-catalyzed N-arylation of NH-containing heterocycles and sulfonamides with arenediazonium tetrafluoroborates

A practical copper-catalyzed N-arylation of NH-containing heterocycles with arenediazonium tetrafluoroborates has been developed using CuCl as catalyst and K₂CO₃ as additive under ligand-free conditions. This reaction system has wide substrate scope including imides, 1H-pyrazole, 1H-tetrazoles, 1,2-benzisothiazol-3(2H)-one, and related sulfonamides and gives moderate to excellent yields (up to 95%) of the desired products. This strategy is very general, simple, environmentally friendly, and tolerant of oxygen.     

Synthesis of SMND-309, a derivate of salvianolic acid B

(E)-2-(6-((E)-2-carboxyvinyl)-2,3-dihydroxyphenyl)-3-(3,4-dihydroxyphenyl) acrylic acid, designated SMND-309, was synthesized starting from 2-hydroxy-3-methoxybenzaldehyde in 12 steps and with an overall yield of 44%. The synthetic key features were the conversion of aryl aldehyde into aryl acetic acid for one-carbon extended, the Perkin condensation, and the Heck coupling for construction of α,β-unsaturated ester.     

Acid-mediated domino reaction of ortho-carbonylated alkynyl-substituted arylaldehydes with phenols: Rapid access to fused indeno[2,1-c]chromen-7-one derivatives

Acid-mediated domino reaction of ortho-carbonylated alkynyl-substituted arylaldehydes with phenols is described. The implement of this reaction can provide directly a variety of tetracyclic indeno[2,1-c]chromen-7-one products in good yields. The mechanism was proposed to be a domino indanone ring formation/ortho-alkylation of phenols/dehydrated cyclization for the formation of polycyclic skeleton. In addition, several interesting dimeric products containing a pentacyclic scaffold were also afforded stereoselectively albeit in moderate yields. The present transformations feature the use of simple acid catalyst, short reaction time and good substrate scope.