MOLECULES
·
2019
·Vol. 24
·期 2
·256
·
IF 3.06
Xuchao Jia,Dan Yang,Yue Yang,Haihui Xie
The fruit ofAverrhoa carambolaL. (Oxalidaceae), commonly known as star fruit or carambola, is popular in tropical and subtropical regions. Carotenoid-derived components, mainly C13- and C15-norisoprenoids, contribute greatly to the flavor of star fruit. Previously reported norisoprenoids were tentatively identified by GC-MS analysis after enzymatic hydrolysis. To gain accurate information about glycosidically bound flavor precursors in star fruit, a phytochemical study was conducted, which led to the isolation of 16 carotenoid derivatives—One new C13-norisoprenoid glucoside, (5R,6S,7E,9R)-5,6,9-trihydroxy-7-megastigmene 9-O-β-d-glucoside (1); one new C15-norisoprenoid, (6S,7E,10S)-Δ9,15-10-hydroxyabscisic alcohol (11); and 14 known ones, of which 12 were in glucoside form. The structures of the two new compounds were elucidated on the basis of extensive spectroscopic data analysis and chemical reaction. Compound11was a rare C15-norisoprenoid with a double bond between C-9 and C-15, and its possible biogenetic pathway was proposed. The known compounds were identified by comparison of their mass and nuclear magnetic resonance (NMR) data with those reported in the literature. The structure identification of one new (1) and seven known (3–7,9, and10) C13-norisoprenoid glucosides from the genusAverrhoafor the first time enriches the knowledge of carotenoid-derived flavor precursors in star fruit.Keywords:Averrhoa carambola;star fruit;flavor precursor;C13-norisoprenoid glucoside;C15norisoprenoid
研究领域:
植物化学
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风味化学
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食品科学
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产品关联
DOI
PubMed
高影响因子
ACS Synthetic Biology
·
2018
·
IF 5.316
Zhen Yao,Pingping Zhou,Bingmei Su,Sisi Su,Lidan Ye,Hongwei Yu
Isoprene, as a versatile bulk chemical, has wide industrial applications. Here, we attempted to improve isoprene biosynthesis in Saccharomyces cerevisiae by simultaneous strengthening of precursor supply and conversion via a combination of pathway compartmentation and protein engineering. At first, a superior isoprene synthase mutant ISPSLN was created by saturation mutagenesis, leading to almost 4-fold improvement in isoprene production. Subsequent introduction of ISPSLN to strains with strengthened precursor supply in either cytoplasm or mitochondria implied an imperfect match between the synthesis and conversion of the isopentenyl pyrophosphate (IPP)/dimethylallyl diphosphate (DMAPP) pool. To reconstruct metabolic balance between the upstream and downstream flux, additional copies of diphosphomevalonate decarboxylase gene (MVD1) and isopentenyl-diphosphate delta-isomerase gene (IDI1) were introduced into the cytoplasmic and mitochondrial engineered strains. Finally, the diploid strain created by mating the above haploid strains produced 11.9 g/L of isoprene, the highest ever reported in eukaryotic cells.
研究领域:
生物技术
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代谢工程
·
合成生物学
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产品关联
DOI
PubMed
高影响因子
NEW JOURNAL OF CHEMISTRY
·
2022
·Vol. 46
·期 17
·8277-8283
·
IF 3.925
Yanchen Huo,Xiang Hu,Jixing Wang,Hongfan Hu,Xiaochao Shi
Amido-trihydroquinoline ligated rare-earth metal complexes have been synthesized, and in combination with a borate, all these complexes (except 2-Sc) showed moderate catalytic activities for isoprene polymerization to generate 1,4-enriched polyisoprene. In particular, the 2-Y-based catalytic system promoted the isoprene polymerization in a well-controlled manner. The alkylaluminium (AlR3, R = Me, Et, iBu) exerted a different influence on the polymerization, and AlMe3 enhanced not only the catalytic reactivity but also the 1,4-selectivity significantly. Considering the influence of the polar sequence on improving the surface property of the non-polar polymer, we further successfully realized the polymerization of ε-caprolactone and its block copolymerization with isoprene by utilizing the active yttrium-polyisoprene species as the marcointiator. The fact that the higher content of the hydrophilic PCL sequence in the copolymer gave a lower WAC, proved the tunable modification of the copolymer's surface hydrophilicity.
研究领域:
有机化学
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高分子化学
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催化化学
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产品关联
DOI
高影响因子
JOURNAL OF APPLIED POLYMER SCIENCE
·
2016
·Vol. 134
·期 1
·
IF 1.866
Zhaowei Wang,Zhixia Wen,Xing Li,Junwei Yu,Xiaoxuan Liu
The preparation of the high cis −1,4-polyisoprene by Ziegler-Natta catalysis system was studied. The effect of Al-Ti catalysts modified by ethers with different structures which are different electron donor reagent on polymerization of isoprene has been mainly investigated. By the measurement method of the monomer conversion, FTIR, and 1 H NMR spectroscopy, the influence of, respectively, added diphenyl ether, anisole, dibutyl ether, or methyl tert -butyl methyl ether as a third active component on the heterogeneous TiCl 4 -Al( i -Bu) 3 -ether catalyst activity and microstructure of synthetic polyisoprene was analyzed. By the adding of diphenyl ether or dibutyl ether, the process of prefabricated heterogeneous catalyst is quickly and catalyst particle quantity is large. The polymerization conversion is high and the microstructure cis −1,4 content of the resulting polymer can reach 92%. But Al( i -Bu) 3 added anisole or methyl tert -butyl methyl ether hard to cooperate with TiCl 4 . © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133 , 44357.
研究领域:
高分子化学
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催化化学
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功能材料
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合成高分子
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配位聚合
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DOI
高影响因子
CARBON
·
2022
·
IF 11.307
Xiang Yu,Yue Zhan,Tingting Fan,Yuqi Zhang,Shunqin Liang,Limin Sun,Xiaoli Hu,Weiping Fang,Zhou Chen,Xiaodong Yi
The stabilization and transport of the reactants, intermediates and products are significant to rational design of an industrial catalyst. In this work, we encapsulated the surface of Pd/g-C 3 N 4 catalyst with acrylic acid (AA) using a photo-induced grafting method to mimic the 3-dimensional nature of enzymes. A combined characterization and ab initio calculation revealed that AA ligands on the surface controlled the adsorption and diffusion behaviors of the reactants, rather than alter the electronic or geometric properties of Pd active centers. The optimized catalyst (Pd/CNA-4) significantly enhances isoprene partial hydrogenation activity without a decline in semi-hydrogenation selectivity. This approach can be further optimized by changing the types of the encapsulating ligands and can meet other specific catalytic reactions to regulate their conversion and selectivity and is therefore expected to extend to other areas of heterogeneous catalysis .
研究领域:
催化化学
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材料科学
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理论化学
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产品关联
DOI
高影响因子
Polymers
·
2016
·Vol. 8
·期 11
·389
·
IF 2.944
Lihua Guo,Xinyu Jing,Shuoyan Xiong,Wenjing Liu,Yanlan Liu,Zhe Liu,Changle Chen
A series of alkyl- and aryl-substituted iminopyridine Fe(II) complexes1a–7aand Co(II) complexes2b,3b,5b, and6bwere synthesized. The activator effect, influence of temperature, and, particularly, the alkyl and aryl substituents’ effect on catalytic activity, polymer molecular weight, and regio-/stereoselectivity were investigated when these complexes were applied in isoprene polymerization. All of the Fe(II) complexes afforded polyisoprene with high molecular weight and moderatecis-1,4 selectivity. In contrast, the Co(II) complexes produced polymers with low molecular weight and relatively highcis-1,4 selectivity. In the iminopyridine Fe(II) system, the alkyl and aryl substituents’ effect exhibits significant variation on the isoprene polymerization. In the iminopyridine Co(II) system, there is little influence observed on isoprene polymerization by alkyl and aryl substituents.Keywords:iminopyridine;Iron(II);Cobalt(II);isoprene polymerization;selectivity
研究领域:
化学
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高分子科学
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产品关联
DOI
PubMed
高影响因子
COMBUSTION AND FLAME
·
2022
·
IF 5.767
Guanyi Chen,Weimeng Ding,Zhanjun Cheng,Jinglan Wang,Lili Xing,Wang Li,Yunrui He,Fawei Lin,Jiuzhong Yang,Long Zhao,Beibei Yan
Isoprene (2-methyl-1,3-butadiene) is not only the main component in gasoline and a potential fuel additive, but also is considered an important precursor of polycyclic aromatic hydrocarbons. To better understand the isoprene pyrolysis process , the pyrolysis experiments of isoprene in a flow reactor were performed at p = 30 Torr for T = 1056 – 1446 K, and p = 760 Torr for T = 850 – 1231 K. More than twenty pyrolysis species, especially radicals (methyl, propargyl, and but‑2‑yne-1-yl), isomers (allene/propyne, buta-1,2,3-triene/vinylacetylene, 1,3-butadiene/1-butyne), and aromatics (benzene, toluene, phenylacetylene, styrene , indene, and naphthalene), were identified and their mole fraction profiles were measured using synchrotron vacuum ultraviolet photoionization mass spectrometry . The potential energy surfaces of the unimolecular decomposition, H/CH 3 -abstraction, and H/CH 3 -addition reactions of isoprene were also calculated using quantum chemical calculations at the CBS-QB3 level. Based on the experimental and theoretical results, a detailed kinetic model was developed and validated against the pyrolysis experimental dataset of isoprene from this work and Grajales-González et al. H-addition reactions on the double bond and H-abstraction reactions by H/CH 3 radicals controlled the consumption of isoprene. The C–H bond dissociation reaction on the –CH 3 was the dominant unimolecular reaction in comparison with the isomerization reactions. Abundant aromatics were produced in isoprene pyrolysis, especially at atmospheric pressure, which is ascribed to the high-level concentration of C(2)–C(4) hydrocarbons formation, such as acetylene, ethylene, allene, propyne , 1,3-butadiene, etc.
研究领域:
化学动力学
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燃料化学
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产品关联
DOI
高影响因子
BMC Chemistry
·
2023
·Vol. 17
·期 1
·1-17
·
IF 4.6
Liang Min,Dai Suyi,Cheng Haijun,Yu Chang,Li Weiguang,Lai Fang,Yang Kang,Ma Li,Liu Xiongmin
In this study, the oxidation characteristics of isoprene were investigated using a custom-designed mini closed pressure vessel test (MCPVT). The results show that isoprene is unstable and polymerization occurs under a nitrogen atmosphere. Under an oxygen atmosphere, the oxidation process of isoprene was divided into three stages: (1) isoprene reacts with oxygen to produce peroxide; (2) Peroxides produce free radicals through thermal decomposition; (3) Free radicals cause complex oxidation and thermal runaway reactions. The oxidation of isoprene conforms to the second-order reaction kinetics, and the activation energy was 86.88 kJ·mol −1 . The thermal decomposition characteristics of the total oxidation product and purified peroxide mixture were determined by differential scanning calorimetry (DSC). The initial exothermic temperatures T on were 371.17 K and 365.84 K, respectively. And the decomposition heat Q DSC were 816.66 J·g −1 and 991.08 J·g −1 , respectively. It indicates that high concentration of isoprene peroxide has a high risk of thermal runaway. The results of thermal runaway experiment showed that the temperature and pressure of isoprene oxidation were prone to rise rapidly, which indicates that the oxidation reaction was dangerous. The reaction products of isoprene were analyzed by gas chromatography-mass spectrometry (GC–MS). The main oxidation products were methyl vinyl ketone, methacrolein, 3-methylfuran, etc. The main thermal runaway products were dimethoxymethane, 2,3-pentanedione, naphthalene, etc. Based on the reaction products, the possible reaction pathway of isoprene was proposed.
研究领域:
化学工程
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安全科学
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产品关联
DOI
PubMed
高影响因子
POLYMER SCIENCE SERIES B
·
2016
·Vol. 58
·期 5
·495-502
·
IF 0.737
Geng Jieting,Sun Yanjie,Hua Jing
Polyisoprene with relatively high content of 1,2/3,4 structure was synthesized using a novel catalyst system composed of MoO 2 Cl 2 supported by phosphorus ligand and Al(OPhCH 3 )( i -Bu) 2 as co-catalyst. The effects of phosphites, phosphates and phosphoric acid as ligands were investigated in the coordination polymerization of isoprene in the chosen catalyst system. The studied ligands significantly affected the catalytic activity of the Mo–Al catalytic active center without significant effect on the stereoselectivity. Mo(VI)-based catalyst system was proved to be highly effective in the polymerization of isoprene even at low [Al]/[Mo] ratio (10), affording polyisoprene with 1,2- and 3,4-% structural units in the range of 44.6–52.5%, high molecular weights M
n ~ 10 5 , and relatively broad molecular weight distributions ( M
w / M
n = 3.0–4.4). The effect of molar ratio of phosphorous ligand to Mo-catalyst on catalyst activity of isoprene polymerization was discussed, and the structures of Mo–phosphite complexes were preliminarily studied by IR.
研究领域:
材料科学
·
催化化学
✓ 已验证
DOI
高影响因子
CARBOHYDRATE POLYMERS
·
2024
·
IF 10.7
Huanjuan Sun,Xuehui Wang,Zhigang Wang
Sustainable cellulose- graft -diblock copolymers (cellulose- graft -polyisoprene- block -polylactide, MCC- g -PI- b -PLLA, MCC was chemically-modified microcrystalline cellulose) were designed and delicately synthesized for the first time by a mild and facile procedure via combining ring-opening polymerization and reversible addition-fragmentation chain transfer polymerization techniques, which conquered the difficulties in synthesis due to the distinct chemical properties among the MCC backbone, PI and PLLA blocks. Two separate glass transition temperatures were detected for MCC- g -PI- b -PLLA copolymers by differential scanning calorimetry, indicative of microphase separation, consistent with small-angle X-ray scattering and atomic force microscopy measurements. The α -form crystals of PLLA outer blocks were revealed by wide-angle X-ray diffraction measurement. The monotonic and step-cyclic tensile tests revealed that the mechanical property could be tuned by changing the molecular mass of PI midblock. The two ends of the soft PI midblock were anchored by rigid cellulose backbone and hard PLLA outer block, respectively, which served as physical crosslinking points. The rigid cellulose backbones brought the PI rubbery domains and PLLA hard domains together to form a whole hierarchical microstructure, endowing the copolymers with distinguished mechanical property. This work provided a feasible approach to producing environmental-friendly cellulose-based copolymers with fully biomass-derived feedstocks, having a profound impact on the development of sustainable polymer-based materials.
研究领域:
材料科学
·
高分子化学
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF BIOTECHNOLOGY
·
2014
·
IF 2.884
Xiaomei Lv,Wenping Xie,Wenqiang Lu,Fei Guo,Jiali Gu,Hongwei Yu,Lidan Ye
To explore the capacity of isoprene production in Saccharomyces cerevisiae , a rational push-pull-restrain strategy was proposed to engineer the mevalonic acid (MVA) and acetyl-CoA pathways. The strategy can be decomposed into the up-regulation of precursor supply in the acetyl-CoA module and the MVA pathway (push-strategy), increase of the isoprene branch flux (pull-strategy), and down-regulation of the competing pathway (restrain-strategy). Furthermore, to reduce the production cost arising from galactose addition and meanwhile maintain the high expression of Gal promoters, the galactose regulatory network was modulated by Gal80p deletion. Finally, the engineered strain YXM10- ispS-ispS could accumulate up to 37 mg/L isoprene (about 782-fold increase compared to the parental strain) under aerobic conditions with glycerol-sucrose as carbon source. In this way, a new potential platform for isoprene production was established via metabolic engineering of the yeast native pathways.
研究领域:
生物化学
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合成生物学
·
代谢工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY
·
2019
·Vol. 57
·期 7
·767-775
·
IF 2.591
Xianhui Zhang,Guangqian Zhu,Qaiser Mahmood,Mengmeng Zhao,Liang Wang,Chuyang Jing,Xiaowu Wang,Qinggang Wang
A stereoselectivity switchable polymerization of isoprene has been developed, which is catalyzed by iminoimidazole-Co(II) and -Fe(II) complexes. The influence of substituents ranging from electron donating to the electron withdrawing on the iminoimidazole-Co(II) and -Fe(II) catalysts is investigated for isoprene polymerization. Two sets of iminoimidazole-Co(II) and -Fe(II) complexes have been prepared and fully characterized. X-ray crystallography analysis reveals that the complexes Co1 and Fe1 adopt distorted tetrahedral geometries. In the presence of AlEt 2 Cl as co-catalyst, all the Co(II) complexes are active and the catalytic activity is highly dependent on the molar ratio of Al/Co. All the Co(II) complexes exhibit higher activities at low Al/Co ratio. Compared with the Co(II) complexes, the Fe(II) complexes are essentially inactive under the identical condition. However, on activation with combination of AlEtCl 2 and [Ph 3 C][B(C 6 F 5 ) 4 ], both Co(II) and Fe(II) complexes display high activities with good conversions of isoprene (up to >99%). Additionally, low molecular weight and high trans -1,4-unit (>96%) selectivity are characteristics of the resultant polyisoprene. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019 , 57 , 767–775
研究领域:
化学
·
材料科学
✓ 已验证
产品关联
DOI
高影响因子
危险品化学品经营许可证（带存储）