查找使用阿拉丁产品的科研文献

The effect of imidazolated PPO with different alkyl chains on its performance as a high temperature proton exchange membrane

Shanshan Wang,Qifeng Li,Fanghui Wang

Designed and synthesized a series of imidazolium-functionalized Poly (2, 6-dimethyl-1, 4-phenylene oxide) (Im-PPO) containing pendant imidazole groups, which were used to supply functional sites for acid–base interaction with the doping phosphoric acid. The imidazolium-functionalized Poly (2, 6-dimethyl-1, 4-phenylene oxide) membranes obtained by the solution-casting method were doped with phosphoric acid (PA). The PA content, swelling, and tensile strength of the different membranes doped with PA were measured. With the increase of the length of side chains on the imidazole groups, the membrane showed different properties. The proton conductivity at a level of 3.7 × 10−2 S/cm was achieved at 160°C by the MeIm-PPO imidazolium composite membrane.

Mushroom (Agaricus bisporus) polyphenoloxidase inhibited by apigenin: Multi-spectroscopic analyses and computational docking simulation

Zhiqiang Xiong,Wei Liu,Lei Zhou,Liqiang Zou,Jun Chen

It has been revealed that some polyphenols can prevent enzymatic browning caused by polyphenoloxidase (PPO). Apigenin, widely distributed in many fruits and vegetables, is an important bioactive flavonoid compound. In this study, apigenin exhibited a strong inhibitory activity against PPO, and some reagents had synergistic effect with apigenin on inhibiting PPO. Apigenin inhibited PPO activity reversibly in a mixed-type manner. The fact that inactivation rate constant ( k ) of PPO increased while activation energy ( E a ) and thermodynamic parameters (Δ G , Δ H and Δ S ) decreased indicated that the thermosensitivity and stability of PPO decreased. The conformational changes of PPO were revealed by fluorescence emission spectra and circular dichroism. Atomic force microscopy observation suggested that the dimension of PPO molecules was larger after interacting with apigenin. Moreover, computational docking simulation indicated that apigenin bound to PPO and inserted into the hydrophobic cavity of PPO to interact with some amino acid residues.

Efficient L-phosphinothricin production by engineered Escherichia coli co-expressing glutamate dehydrogenase, glucose dehydrogenase and NAD kinase with NADPH regeneration

Shu-Ping Zou,Wei Ding,Yu-Yue Han,Kun Niu,Ya-Ping Xue,Yu-Guo Zheng

L-Phosphinothricin (L-PPT) is the active compound of a broad-spectrum herbicide. In this study, we biosynthesized L-PPT via the asymmetric reduction of 2-carboxy-4-(hydroxymethylphosphoryl) butyric acid (PPO) using a whole-cell biocatalyst. Glutamate dehydrogenase from Pseudomonas moorei ( Pm GluDH), Glucose dehydrogenase from Exiguobacterium sibiricum ( Es GDH) and NAD kinase from Corynebacterium glutamicum ( Cg NADK) were coexpressed in E. coli , significantly increasing the catalytic efficiency by regenerating more NADPH to promote PPO reduction. Following the optimization of balancing the co-expression of the three enzymes in pETDuet-1 and pCDFDuet-1, the coexpressing strain increases in the intracellular NADP(H) concentration to 54.9 μmol/g DCW, which was 3.8-fold higher than the control. The co-expression system exhibited optimal activity at a temperature of 35°C, pH 7.5, and the glucose to PPO molar ratio of 1.4:1. In a 30 L bioconversion system the final concentration and productivity of L-PPT reached 79.8 g/L (>99% ee ) and 1440 g/(L·d), respectively. These results will contribute to the industrial biological production of L-PPT.

Degradations of aroma characteristics and changes of aroma related compounds, PPO activity, and antioxidant capacity in sugarcane juice during thermal process

Lu Wang,Weili Deng,Peng Wang,Wencheng Huang,Jiamin Wu,Tingyu Zheng,Jiebo Chen

Alterations of aroma properties and aroma-related attributes of sugarcane juice during thermal processing under different temperatures (90, 100, and 110 ℃) and treating time (10 s, 20 s, and 30 s) were assessed in this study. Changes in the volatility of aroma compounds were extremely complicated and respected to thermal processing conditions. Fructose, serine, and glutanic acid of sugarcane juice were increased at first and decreased at the end of treatment at high temperature. Phenolic compounds and PPO activity presented the decrease trends throughout the thermal treatment. The thermal processing of sugarcane juice could be roughly divided into three stages based on the cluster analysis of all the data in this study. Sugars, amino acids, and phenolic compounds might be important potential precursors of aroma deteriorating reactions. The comprehensive analysis of aroma relevant compounds and enzyme activities was beneficial for the investigation of degradation mechanism of aroma for sugarcane juice, and providing a theoretical basis for optimization of juice processing. Practical Application This study demonstrated the changing process of aroma quality and associated compounds in sugarcane juice during thermal processing. This could help to find out the reasons of aroma degradations in sugarcane juice and other thermal sensitive juice. Our manuscript created a paradigm for future studies on the aroma quality control and parameter optimization during the processing of fruit and vegetable juice.

The Synthesis of Poly(2,6-dimethyl-1,4-phenylene oxide)/Polymethylmethacrylate Alloy in Aqueous Medium via a One-Pot Method

Shang Mengyao,Wang Huan,Shentu Baoqing,Weng Zhixue

An environmentally friendly one-pot synthetic method based on green chemistry was developed to prepare thermodynamically partially compatible poly(2,6-dimethyl-1,4-phenylene oxide)/poly(methylmethacrylate) (PPO/PMMA) alloy in water. The oxidative polymerization of 2,6-dimethylphenol in alkaline aqueous solution was firstly conducted and then methyl methacrylate (MMA) was added into the reactor before the end of polymerization. MMA could penetrate into PPO particles and then in situ reverse atom transfer radical polymerization (RATRP) of methyl methacrylate was initiated by 2,2'-azobis[2-(2-imidazolin-2-yl)propane] dihydrochloride after the oxidative polymerization. Both the oxidative polymerization of 2,6-dimethylphenol and RATRP of methyl methacrylate were catalyzed by the complex of CuCl 2 and 4-dimethylaminopyridine. Finally, thermodynamically partially compatible PPO/PMMA alloy was successfully prepared which possessed a multi-layer core-shell structure with two polymers embedded in each other.

Evaluating Chinese tea varieties through differential analysis of PPO isoenzymes and non-volatile metabolites and construction of adaptability models for black tea

Jinjie Hua,Liyue Yang,Jianqiang Ma,Xiwang Li,Ting An,Fenglan Zhang,Ming Chen,Xinxin Lv,Jiayi Zhu,Jinjin Wang,Haibo Yuan,Yongwen Jiang

Tea varieties are key factors influencing tea type and flavor quality. However, the key biochemical indicators biochemical indicators associated with tea varietal suitability remain unclear, and the traditional phenol-ammonia ratio is insufficient as an evaluation criterion. Therefore, identifying reliable biochemical markers for evaluating tea varietal suitability is important for optimizing tea processing and product quality. We aimed to identify key biochemical indicators associated with tea varietal suitability for black and green tea processing and to establish a predictive model for evaluating tea varietal adaptability. Molecular biology and targeted metabolomics approaches were used to analyze polyphenol oxidase (PPO) activity, the expression of three PPO isozymes, and the contents of 60 non-volatile metabolites (NVMs) in fresh leaves from 20 representative tea varieties. Variable importance in projection, S-plot, taste active value, and classification analyses were applied to identify key differential indicators. A predictive model for tea varietal suitability was subsequently developed using data preprocessing and regression analysis. Nine key differential biochemical indicators, including epigallocatechin gallate, epicatechin gallate, epigallocatechin, epicatechin, catechin, myricetin-3-O-galactoside, theaflavin-3-3′-di-O-gallate, theanine, and glutamic acid, together with three enzyme-related indicators, namely PPO activity and the expression levels of PPO2 and PPO4, were identified. Tea varieties suitable for black tea exhibited high levels of epigallocatechin gallate, epicatechin gallate, theaflavin-3-3′-di-O-gallate, and PPO activity, particularly PPO4 expression. In contrast, tea varieties suitable for green tea showed high levels of epigallocatechin, epicatechin, theanine, glutamic acid, and myricetin-3-O-galactoside content. A 1DER+MINMAX data preprocessing method and predictive model effectively evaluated tea varietal suitability. This study identified key biochemical indicators associated with tea varietal suitability and established a predictive model for evaluating tea adaptability for black and green tea processing. These findings provide theoretical and technical support for the efficient utilization of fresh leaf leaves and tea product development.

Synthesis, characterization, and self-assembly of linear poly(ethylene oxide)-block–poly(propylene oxide)-block–poly(ε-caprolactone) (PEO–PPO–PCL) copolymers

Lifang Xu,Zhiqing Zhang,Fang Wang,Dongdong Xie,Shan Yang,Tao Wang,Lijuan Feng,Chengchai Chu

Amphiphilic triblock copolymers of PEO–PPO–PCL with various block compositions have been synthesized by ring-opening polymerization (ROP) of ε-caprolactone (ε-CL) initiated by the OH group of methoxy–poly(ethylene oxide)–poly(propylene oxide) (Me–PEO–PPO). Their structures were confirmed by Fourier transform infrared (FT-IR) measurements, and their self-assembly in aqueous solution was studied using fluorescence spectroscopy, transmission electron microscopy (TEM), UV–vis spectra, differential scanning calorimetry (DSC), and surface tension. For the copolymers studied in this paper, the critical aggregation concentrations (CAC) ranged from 5   ×   10 3 to 2   mg/L. The critical micelle concentrations (CMC) decreased with increasing PCL block length, and the downtrend was more significant in the short PCL block length. All of the three copolymers were capable of solubilizing hydrophobic molecules (pyrene) in aqueous solution and copolymers with a longer PCL block exhibited a stronger solubilizing ability. The TEM images showed that the size and morphology of the aggregations could be tuned by varying the compositions or the concentration.

High-temperature proton exchange membrane with dual proton transfer channels by incorporating phosphonic acid functionalized siloxane into poly(2,6-dimethyl-1,4-phenyleneoxide) (PPO)

Xi Zhu,Chunhui Shen,Shanjun Gao,Huaiyang Jin,Xiangze Cheng,Chenliang Gong

A series of high-temperature proton exchange membranes were prepared by incorporating phosphonic acid functionalized siloxane synthesized from Amino Trimethylene Phosphonic Acid (ATMP) and 3-Aminopropyltriethoxysilane (APTES) into cross-linked 1-Methylimidazole-functionalized poly(2,6-dimethyl-1,4-phenyleneoxide) (PPO) backbone. The structural characteristics of membranes were investigated using FT-IR, 1 H NMR and XRD , indicating that ATMP and backbones of membranes were successfully immobilized into cross-linking Si-O-Si networks formed by hydrolysis-polycondensation of APTES. The resultant membranes named as HTM-X exhibited superior oxidative resistance, mechanical properties and dimensional stability, even the thermal stability was up to 210 °C. The proton conductivities of membranes were also measured under different temperature. The result showed that HTM-15 membrane, whose content of phosphonic acid functionalized siloxane was 15 wt%, possessed the highest proton conductivity of 8.48 × 10 −2  S cm −1 at 160 °C and low relative humidity (5%) with the contribution of dual proton transfer channels of acid-base pairs and continuous hydrogen bond networks. Therefore, this novel membrane acts as a potential candidate for proton exchange membranes operating at elevated temperature.

Synthesis of a novel demulsifier by one-pot synthesis using two PEO-PPO demulsifiers as materials and the study of its demulsification performance

Fei Wang,Shenwen Fang,Ming Duan,Yan Xiong,Xiujun Wang

Metabolomic and transcriptomic profiles reveal the mechanism of browning inhibition of Pueraria lobata by heat treatment

Junping Liu,Junmin Huang,Kaibo Yu,Xiaoyong Chang,Yangyang Li,Xiaowei Chen,Shengfeng Peng,Lei Zhou,Wei Liu

This study investigated the mechanism of browning inhibition by heat treatment (70 °C for 5 min) by analyzing its effects on polyphenol oxidase (PPO) activity, browning index, antioxidant activity, metabolite and gene expression profiles using physiological, metabolomic and transcriptomic approaches. Heat treatment inhibited PPO activity and delayed the browning of Pueraria lobata , while increasing free radical scavenging activity and total flavonoid content. Metabolomic analyses revealed that catechins, caffeic acid, tyrosine and coumaric acid might be the major metabolites associated with the browning of Pueraria lobata , whereas flavonoid and isoflavonoid metabolites might be beneficial for delaying browning. Multi-omics analysis revealed that the tyrosine metabolism and isoflavone biosynthesis pathways were enriched and played crucial regulatory roles in browning. This study provides a practical strategy for improving quality in post-harvest processing and deep processing of Pueraria lobata . Future research need focus on the spatial variation analysis of these browning-related metabolites in Pueraria lobata .

Highly permselective tadpole-type ionic anion exchange membranes for electrodialysis desalination

Biaowen Wei,Jun Feng,Caidi Chen,Shixi Zhong,Shijun Liao,Yigang Yu,Xiuhua Li

A series of tadpole-type ionic ionomers PPO-DMODAs with long alkyl side chains designed for electrodialysis (ED) desalination were synthesized successfully from dimethyloctadecylamine (DMODA) and brominated poly (2,6-dimethyl-1,4-phenylene oxide) (BPPO). The series of AEMs display stably low water uptakes ranging from 6.2% to 15.1% and high dimensional stabilities with swelling rations of 1.9%–4.8% at temperatures of 25 °C–60 °C. The nano-phase separated tadpole-type ionic structures ensure that the PPO-DMODAs membranes show excellent permselectivities with values above 94.6% and outstanding ED performances in the mostly reported desalination system of NaCl aqueous solutions. Especially, PPO-DMODA-3 surpasses commercial membrane TWEDA1 in ED competitions and ED-stability matches with current efficiency (η) of 88.7%, salt flux (J) of 80.61 mg m −2  s −1 , energy consumption (EC) of per kg of NaCl of 2.56 kWh kg −1 and η retentions of the repeated runs higher than 97% of that of the origin run. Moreover, PPO-DMODA-3 membrane obtained from the ethanol solution exhibits stable aggregate structure and ED performances comparable to those of the PPO-DMODA-3 membranes cast with NMP and TCE solutions. Good solubility of PPO-DMODAs in ethanol offers an environmentally friendly green method to fabricate ED AEMs. In consideration of the advantages of low cost, simple synthesis process and green membrane casting technology, PPO-DMODA-3 membrane has a strong potential for ED-desalination application.

Aggregation and conformational change of mushroom (Agaricus bisporus) polyphenol oxidase subjected to atmospheric cold plasma treatment

Yifan Zhu,Mubango Elliot,Yanhong Zheng,Jing Chen,Dongzhi Chen,Shanggui Deng

Atmospheric cold plasma (ACP) is a novel nonthermal technology with potential applications in maintaining and improving food quality. The effect of ACP on the activity and structure of mushroom ( Agaricus bisporus ) polyphenol oxidase (PPO) was evaluated. Results demonstrated that the dielectric barrier discharge (DBD) based plasma technology could inactivate PPO (up to 69%) at 50 kV with the increased concentrations of H 2 O 2 and NO x . An obvious enhancement of surface hydrophobicity was observed, whereas a gradual reduction of total sulfhydryl content was recorded with the increasing exposure time. Data from circular dichroism, atomic force microscopy, particle size distribution and fluorescence spectra displayed the rearrangement of secondary structure and disruption of the tertiary structure. Red shifts of fluorescence spectra showed positive correlations with the inactivation rate of PPO. Therefore, ACP treatment could be served as an alternative approach to inactivate undesirable enzymes to minimize the loss of food nutrition and quality.