POLYMER TESTING
·
2020
·
IF 3.275
Zhipeng He,Huichao Liu,Guang Yang,Chi Jiang,Muwei Ji,Jiali Yu,Mingliang Wang,Caizhen Zhu,Jian Xu
Cyclization reaction of poly(acrylonitrile-co-2-acrylamido-2-methylpropane sulfonic acid) [P(AN-co-AMPS)] copolymer during thermal oxidative stabilization (TOS) process was investigated by FTIR and two dimensional (2D) correlation analysis technique. The results showed the mechanism of cyclization reaction at different temperatures were varying. At 200 °C, the cyclization reactions generated by autocatalytic cyclization mechanism. While at higher temperatures, the cyclization reactions took place through ionic cyclization mechanism and free radical cyclization mechanism. The AMPS comonomer could reduce the heat release of cyclization reactions and improve the stability at 200 and 230 °C. At higher temperatures, the cyclization reactions were facilitated rapidly. However, the oxidation and degradation reactions were also intense, which will cause the molecular chain to break and defects in the final carbon fibers (CFs). This research has theoretical guiding significance for the optimization of heat treatment conditions for PAN copolymers used as CFs.
研究领域:
高分子化学
·
材料科学
·
光谱学
✓ 已验证
DOI
高影响因子
Synthetic and Systems Biotechnology
·
2023
·
IF 4.8
Zhongju Ji,Baolian Fan,Yidu Chen,Jingyang Yue,Jiabo Chen,Rongrong Zhang,Yi Tong,Zhongqiu Liu,Jincai Liang,Lixin Duan
Cibotium barometz (Linn.) J. Sm., a tree fern in the Dicksoniaceae family, is an economically important industrial exported plant in China and widely used in Traditional Chinese Medicine. C. barometz produces a range of bioactive triterpenes and their metabolites. However, the biosynthetic pathway of triterpenes in C. barometz remains unknown. To clarify the origin of diverse triterpenes in C. barometz , we conducted de novo transcriptome sequencing and analysis of C. barometz rhizomes and leaves to identify the candidate genes involved in C. barometz triterpene biosynthesis. Three C. barometz triterpene synthases (CbTSs) candidate genes were obtained. All of them were highly expressed in C. barometz rhizomes, consisting of the accumulation pattern of triterpenes in C. barometz . To characterize the function of these CbTSs, we constructed a squalene- and oxidosqualene-overproducing yeast chassis by overexpressing all the enzymes in the MVA pathway under the control of GAL-regulated promoter and disrupted the GAL80 gene in Saccharomyces cerevisiae simultaneously. Heterologous expressing CbTS1, CbTS2, and CbTS3 in engineering yeast strain produced cycloartenol, dammaradiene, and diploptene, respectively. Phylogenetic analysis revealed that CbTS1 belongs to oxidosqualene cyclase, while CbTS2 and CbTS3 belong to squalene cyclase. These results decipher enzymatic mechanisms underlying the origin of diverse triterpene in C. barometz .
研究领域:
植物生物化学
·
分子生物学
·
生药学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
MONATSHEFTE FUR CHEMIE
·
2015
·Vol. 147
·期 6
·1101-1105
·
IF 1.222
Tu Xingzhao,Xiong Jing,Li Zhijie,Zhou Lihong,Emmanouil Christina,Zeng Qingle
Abstract The valuable 2-( tert -butyldisulfanyl)heterocycles were effectively synthesized from 2-mercaptoheterocycles and tert -butanesulfinamide via unusual condensation. The reaction between 2-mercapto sulfur-containing heterocycles and tert -butanesulfinamide was performed under ligand-free CuI-catalyzed conditions. The synthetic processes described herein are simple, cost-efficient, and practical. Furthermore, a plausible mechanism is proposed for this transformation. Graphical abstract
研究领域:
有机化学
·
药物化学
✓ 已验证
DOI
高影响因子
Polymer Chemistry
·
2016
·Vol. 7
·期 29
·4717-4727
·
IF 5.687
Qingfu Ban,Jie Kong
Well-defined hyperbranched polymers with long-chain backbones between the branched points (HyperMacs) are an emerging issue in topological polymers. Owing to the difficult discrimination of branching points interfered with or overlapped by long-chain backbones in nuclear magnetic resonance signals, the fine identification and quantitative characterization of intramolecular cyclization and the calculation of the degree of branching for HyperMacs are always challenges. In this contribution, a convenient expression of the macro-cyclic index (m-CI) was presented and deduced as the ratio of NA/NB of HyperMacs to that of their completely intramolecular cyclized analogues. The physical meaning of m-CI is the similarity of HyperMacs to their completely cyclized analogues. Accordingly, a m-CI closer to 1 means a high degree of intramolecular cyclization, even complete cyclization. The experimental validation via model polymers indicates that m-CI is a facile parameter to analyze intramolecular cyclization of HyperMacs. The increase of the chain length of the backbones between branched points can enhance intramolecular cyclization of HyperMacs accompanied with the increase of the m-CI value. As an original contribution to polymer science, the presentation of m-CI overcomes the difficult problem of quantitative characterization of intramolecular cyclization in long-chain hyperbranched polymers, which is helpful for a good understanding of their relationship between topological structures and properties.
研究领域:
高分子科学
·
材料科学
·
化学工程
✓ 已验证
DOI
高影响因子
Marine Drugs
·
2022
·Vol. 20
·期 11
·688
·
IF 6.085
Jingmin Cui,Yan Sun,Linqing Wang,Qin Miao,Wenqiang Tan,Zhanyong Guo
We successfully prepared a series ofl-arginine Schiff bases acylated chitosan derivatives, aiming to improve the antioxidant activity and antimicrobial activity of chitosan by introducing a furan ring, pyridine ring, andl-arginine structure. The accuracy of the structures of ten compounds was characterized by FT-IR and1H NMR. In terms of DPPH radical scavenging activity, except for compound CR3PCA, the scavenging rate of other compounds was higher than chitosan, especially CRCF and CRBF had strong scavenging abilities. At the same time, in the superoxide-radical scavenging activity assay, CRCF, CRBF, CR3PCA, CR2C3PCA, and CR2B3PCA were comparable to positive control at 1.60 mg/mL. Simultaneously, CRFF, CRCF, and CRBF had a certain inhibitory effect onBotrytis cinerea. Furthermore, the inhibitory effect of CRFF, CRCF, and CR3PCA onStaphylococcus aureuswas very well, close to the positive control at 1.00 mg/mL. CRCF and CR2B3PCA showed better inhibitory effects onEscherichia colithan other compounds. The MTT assay was used to determine the cytotoxicity of the chitosan derivatives, which proved their safety to fibroblast cells. In summary, the study indicated that some of these compounds have the potential for further development and utilization in the preparation of antioxidants and antimicrobial agents.Keywords:chitosan;l-arginine Schiff bases;heterocyclic compounds
研究领域:
生物化学
·
食品科学
·
药学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
POLYMER
·
2021
·
IF 4.43
Bo-Wen Liu,Yu-Fei Lei,Xiao-Feng Liu,De-Ming Guo,Li Chen,Yu-Zhong Wang
Despite the excellent overall performance, the application of polyesters is severely restricted by their inherently high flammability . Although many gratifying results have been achieved through different fire-safety methods, customization is still needed for every specific polymer, thus a generally applicable method is highly desired. Herein, we developed an eco-friendly and general fire-safety method for semi-aromatic polyesters based on the “end-group-capturing” concept. The functional monomer was chemically incorporated into the main chains of a series of semi-aromatic polyesters with similar structures (i.e., polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT) and polybutylene terephthalate (PBT)), and the specific contribution of the fire-safety method was investigated comprehensively. The results showed that the fire safety of all the copolyesters were efficiently improved, while interestingly, the fire safety gradually declined with the increase of the methylene group numbers in their molecular chains. The reason behind this phenomenon was comprehensively studied by both theoretical calculation and experiments. The increasing cyclization tendency of the copolyesters derived from the increase of the methylene group numbers was proved to be responsible for the decrease of the fire safety. The successful application and in-depth mechanism revealed here provide theoretical supports for the development of novel fire-safety polymeric materials.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
高影响因子
CHEMICAL ENGINEERING SCIENCE
·
2016
·
IF 2.75
Genkuo Nie,Xiangwen Zhang,Peijuan Han,Junjian Xie,Lun Pan,Li Wang,Ji-Jun Zou
Biofuels are important alternative for fossil-based fuel but they have either relatively low density or high freezing point and viscosity. Here we reported a simple and efficient route to synthesis biofuel with density comparable to widely used JP-10 fuel as well as good low-temperature properties. Substituted diphenyl methane was synthesized by acid catalytic alkylation of lignin-derived phenols (phenol, anisole, guaiacol) with benzyl ether or benzyl alcohols, and MMT-K10 exhibits better activity than HPW, Amberlyst-15, and Al-MCM-41, due to the modest acid strength and open lamellar structure. High selectivity along with good-to-excellent conversion was obtained under optimized conditions regardless of different reactant used. Then the alkylated product was subjected to hydrogenation with the presence of Pd/C and HZSM-5, and interestingly, intramolecular cyclization reaction occurred to produce a large amount of perhydrofluorene as well as dicyclohexylmethane. Subsequently, biofuel with density as high as 0.93 g/mL and freezing point as low as −40.0 °C was obtained, which surpasses the state-of-art of biofuel reported.
研究领域:
化学工程
·
能源科学
·
生物化学
✓ 已验证
产品关联
DOI
高影响因子
Analytical Methods
·
2018
·Vol. 11
·期 1
·88-96
·
IF 2.073
Wu Zou,Fuchun Gong,Zhong Cao,Jiaoyun Xia,Tingting Gu,Renxing Deng
Artemisinin (ART) and its derivatives are first-line treatment drugs for falciparum malaria and save millions of lives every year. It is very difficult to design specific fluorescent probes for ART because ART has no groups for binding to except for the peroxide group. We find that alkaline-hydrolyzed ART (a-ART) can specifically recognize and react with vitamin B1 (VB1) and produce fluorimetrically detectable thiochromes. Notably, this chemistry is affected by very low concentrations of a-ART in a Tris–HCl buffer solution (pH 7.5) at room temperature, leading to >260-fold enhancement in the blue emission at 442 nm. By making use of the new signaling mechanism, an effective strategy for detecting ART was developed. The fluorescence intensity of the VB1-based probes linearly increased with increasing ART concentration ranging from 1 to 230 μM mL−1, and a detection limit as low as 11.5 nM mL−1 was achieved, making this method more sensitive than other reported UV-vis absorption and electrochemical methods. Moreover, this assay shows good selectivity over other ions and biomolecules. The proposed method was applied for the determination of ART in tablets and dried leaf samples of Artemisia annua L. with satisfactory results, which confirms its great potential for real sample analysis. The designed assay avoids the preparation of fluorescent probes, and all the detection processes are accomplished within 20 min. Therefore, VB1 can offer a simple, highly sensitive and selective sensing model for fluorescence detection of ART.
研究领域:
药物化学
·
分析化学
·
生物医学
✓ 已验证
DOI
高影响因子
JOURNAL OF ANALYTICAL AND APPLIED PYROLYSIS
·
2021
·
IF 5.541
Mei Jiang,Dongmei Bi,Tianyu Wang,Zixiang Gao,Jing Liu
This paper aimed at investigating the co-pyrolysis behavior of cellulose and urea in a fixed bed reactor under N 2 atmosphere. The effects of the proportions of urea in blend and pyrolysis temperatures on the char and the components of bio-oil were investigated. When the proportion of urea was 20 %, the peak area of anhydro sugars was 28.66 % higher than that when the proportion of urea was 0%. Furans and carbonyls were the key intermediates for the formation of nitrogenous heterocyclic compounds (NHCs) from cellulose. The NHCs in the obtained bio-oil mainly are pyrroles, pyrimidines, pyridines, imidazoles and pyrazines. Higher temperature (600℃) was unfavorable for improving the selectivity of NHCs. Co-pyrolysis of cellulose and urea can introduce abundant nitrogen and nitrogenous functional groups into char. In addition, residuals obtained at different residence times have also been characterized by element analysis and FTIR. The results showed that both the amount and the kind of functional groups in the residuals were reduced with the residence time increasing. High value NHCs and nitrogen-rich char were generated by co-pyrolysis of cellulose and urea. Finally, the possible reactions for the generation of NHCs in the bio-oil were given.
研究领域:
能源与燃料
·
化学工程
✓ 已验证
产品关联
DOI
高影响因子
ORGANIC & BIOMOLECULAR CHEMISTRY
·
2020
·Vol. 18
·期 21
·4034-4045
·
IF 3.412
Ming-Hong Liao,Meng Zhang,Dai-Hui Hu,Rui-Han Zhang,Yan Zhao,Shan-Shan Liu,Yun-Xia Li,Wei-Lie Xiao,E Tang
An efficiently divergent intramolecular Friedel–Crafts alkylation by unactivated alkenes with seleniranium ion-controlled Markovnikov/anti-Markovnikov specificities under mild conditions has been investigated. 2-Benzoxepin, isochroman, and isochromene can be produced in one-pot procedures from the same substrate in high yields and with high regio- and stereospecificity. The products are challenging to access via 7-endo-trig carbocyclizations and by 7-endo-trig carbocyclization/rearrangement/6-exo-trig oxycyclization and 6-exo-trig carbocyclization/deselenenylation reaction sequences, respectively. Mechanistic experiments indicated that in addition to the stereospecific anti-addition processes of the cyclization reactions, the formation of a stable carbocation after ring opening of the seleniranium ion leads to an NPSP-mediated 7-endo-trig carbocyclization; the steric hindrance of the seleniranium intermediate controls the regioselectivity when using TPSCA at 60 °C, which promotes 6-exo-trig carbocyclization. Two distinct catalytic cycles were proposed, and the structures of transition states and products were identified by ab initio calculations and X-ray analyses.
研究领域:
有机化学
·
催化化学
✓ 已验证
DOI
PubMed
高影响因子
DYES AND PIGMENTS
·
2021
·
IF 4.889
Kui Wang,Qi-Qi Wang,Mi-Ni Wang,Ya-Jing Xie,Xuan Qiao,Siyang Xing,Bolin Zhu
In this work, a water-soluble fluorescent and colouring macrocycle deprotonated-calixpyridinium was obtained by a simple pH modulatory strategy. This type of fluorescent and colouring macrocyclic skeleton as host will be certainly applied in a large number of fields, especially in the sensing area. Herein, a near white-light emission was carried out by an innovative method of deprotonated-calixpyridinium-based host–guest interactions employing camptothecin sodium as the guest. Moreover, the pH-responsive luminescence color change of calixpyridinium–camptothecin sodium complex was further applied for the high selective detection of arginine in pure water and real samples, which is quite important in the accurate diagnosis of various disorders. The newfound pH-dependent luminescent and colouring properties of calixpyridinium will also provide an alternative idea for the development of other novel fluorescent and colorimetric macrocyclic sensors.
研究领域:
分析化学
·
生物传感
·
医学诊断
✓ 已验证
DOI
高影响因子
ORGANIC & BIOMOLECULAR CHEMISTRY
·
2025
·
IF 2.7
Fei Yuan,Yiyuan Xin,Caifeng Yuan,Zhuo Chen,Tongling Qin,Wenxia Hu,Jiahuan Duan,E Tang
A simple, exogenous-base-free, and NBS-mediated C-selenocyanation/cyclization reaction of enaminones with KSeCN under mild conditions, providing a facile route to 2-aminoselenazole products, has been developed. This efficient protocol is postulated to first undergo the NBS-oxidated polarity reversal of the reactive SeCN- anion to form N-selenocyanosuccinimide as an electrophilic selenium source, which can induce the C-selenocyanation of enaminones and enamino esters, followed by a nucleophilic cyclization promoted by in-situ yielded HBr.
研究领域:
有机化学
·
合成化学
·
硒化学
✓ 已验证
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）