11 results on '"Erna Xun"'
Search Results
2. Immobilization of Laccase for Oxidative Coupling of Trans-Resveratrol and Its Derivatives
- Author
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Tiexin Cheng, Zhi Wang, Tengfei Ji, Lei Wang, Ge Chen, Hong Zhang, Jiaxin Wang, and Erna Xun
- Subjects
laccase ,SBA-15 ,immobilization ,oxidative coupling ,resveratrol ,Biology (General) ,QH301-705.5 ,Chemistry ,QD1-999 - Abstract
Trametes villosa Laccase (TVL) was immobilized through physical adsorption on SBA-15 mesoporous silica and the immobilized TVL was used in the oxidative coupling of trans-resveratrol. Higher loading and activity of the immobilized enzyme on SBA-15 were obtained when compared with the free enzyme. The effects of reaction conditions, such as buffer type, pH, temperature and substrate concentration were investigated, and the optimum conditions were screened and resulted in enzyme activity of up to 10.3 μmol/g·h. Furthermore, the oxidative couplings of the derivatives of trans-resveratrol were also catalyzed by immobilized TVL. The immobilized TVL was recyclable and could maintain 78% of its initial activity after reusing it four times.
- Published
- 2012
- Full Text
- View/download PDF
3. Heavy metals in nectar modify behaviors of pollinators and nectar robbers: Consequences for plant fitness
- Author
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Jixun Guo, Erna Xun, Ji-Min Zhao, and Yan-Wen Zhang
- Subjects
0106 biological sciences ,Plant Nectar ,Pollination ,Health, Toxicology and Mutagenesis ,Foraging ,Zoology ,Flowers ,Biology ,Toxicology ,010603 evolutionary biology ,01 natural sciences ,Plant reproduction ,Pollinator ,Metals, Heavy ,Animals ,Soil Pollutants ,Nectar ,Nectar robbing ,Reproductive success ,Reproduction ,General Medicine ,Plants ,Pollution ,Robbing ,Environmental Monitoring ,010606 plant biology & botany - Abstract
Plants growing in heavy-metal-rich soils can accumulate metals into their nectar. Nectar chemical composition can alter foraging behavior of floral visitors (including pollinators and floral antagonists) and further affect plant reproductive fitness. The role of nectar heavy metals in deterring pollinators (e.g., shortening foraging time) has been recently studied, but their effects on plant reproduction via changes in behaviors of both pollinators and floral antagonists (e.g., nectar robbers) are less understood. We experimentally manipulated four nectar heavy metals (Zn, Cu, Ni, and Pb) in a native ornamental plant, Hosta ensata F. Maekawa, to investigate the effect of nectar metals on plant reproductive success. We also recorded nectar robbing as well as foraging time and visitation rate of pollinators to assess whether nectar metals could alter the behavior of antagonists and mutualists. Although metals in nectar had no significant direct effects on plant reproduction via hand-pollination, we detected their positive indirect effects on components of female fitness mediated by pollinators and nectar robbers. Matching effects on female plant fitness, nectar robbers responded negatively to the presence of metals in nectar, robbing metal-treated flowers less often. Pollinators spent less time foraging on metal-treated flowers, but their visitation rate to metal-treated flowers was significantly higher than to control flowers. Moreover, pollinators removed less nectar from flowers treated with metals. Our results provide the first direct evidence to date that heavy metals in nectar are capable of deterring nectar robbers and modifying pollinator foraging behavior to enhance plant reproductive fitness.
- Published
- 2018
4. Translocation of heavy metals from soils into floral organs and rewards of Cucurbita pepo: Implications for plant reproductive fitness
- Author
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Jimin Zhao, Jixun Guo, Yan-Wen Zhang, and Erna Xun
- Subjects
0106 biological sciences ,Plant Nectar ,Health, Toxicology and Mutagenesis ,Stamen ,Flowers ,010501 environmental sciences ,medicine.disease_cause ,01 natural sciences ,Plant reproduction ,Cucurbita pepo ,Cucurbita ,Pollinator ,Pollen ,Metals, Heavy ,Botany ,medicine ,Nectar ,Animals ,Soil Pollutants ,Hyperaccumulator ,Pollination ,0105 earth and related environmental sciences ,biology ,Reproduction ,fungi ,Public Health, Environmental and Occupational Health ,food and beverages ,General Medicine ,Bees ,biology.organism_classification ,Pollution ,Seeds ,010606 plant biology & botany ,Squash - Abstract
Metals and metalloids in soil could be transferred into reproductive organs and floral rewards of hyperaccumulator plants and influence their reproductive success, yet little is known whether non-hyperaccumulator plants can translocate heavy metals from soil into their floral organs and rewards (i.e., nectar and pollen) and, if so, whether plant reproduction will be affected. In our studies, summer squash (Cucurbita pepo L. cv. Golden Apple) was exposed to heavy-metal treatments during bud stage to investigate the translocation of soil-supplemented zinc, copper, nickel and lead into its floral organs (pistil, anther and nectary) and rewards (nectar and pollen) as well as floral metal accumulation effects on its reproduction. The results showed that metals taken up by squash did translocate into its floral organs and rewards, although metal accumulation varied depending on different metal types and concentrations as well as floral organ/reward types. Mean foraging time of honey bees to each male and female flower of squash grown in metal-supplemented soils was shorter relative to that of plants grown in control soils, although the visitation rate of honeybees to both male and female flowers was not affected by metal treatments. Pollen viability, pollen removal and deposition as well as mean mass per seed produced by metal-treated squash that received pollen from plants grown in control soils decreased with elevated soil-supplemented metal concentrations. The fact that squash could translocate soil-supplemented heavy metals into floral organs and rewards indicated possible reproductive consequences caused either directly (i.e., decreasing pollen viability or seed mass) or indirectly (i.e., affecting pollinators' visitation behavior to flowers) to plant fitness.
- Published
- 2017
5. Kinetic resolution of (R, S)-2-(2-chloro-1-hydroxyethyl) thiophene via immobilizing lipase fromAlcaligenes sp. onto magnetic nanoparticles
- Author
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Erna Xun, Jimin Zhao, Jixun Guo, and Zhi Wang
- Subjects
biology ,Renewable Energy, Sustainability and the Environment ,Chemistry ,General Chemical Engineering ,Organic Chemistry ,Enantioselective synthesis ,Substrate (chemistry) ,Transesterification ,Pollution ,Kinetic resolution ,Inorganic Chemistry ,chemistry.chemical_compound ,Fuel Technology ,Yield (chemistry) ,biology.protein ,Thiophene ,Organic chemistry ,Lipase ,Enantiomeric excess ,Waste Management and Disposal ,Biotechnology - Abstract
BACKGROUND (S)-2-(2-chloro-1-hydroxyethyl) thiophene is one of the most important intermediates for the synthesis of (S)-duloxetine. The preparation of (S)-2-(2-chloro-1-hydroxyethyl) thiophene could be realized from its racemate via enzymatic resolution. This study aimed to prepare an easy-recycling immobilized lipase with excellent performance and use it to obtain (S)-2-(2-chloro-1-hydroxyethyl) thiophene with high enantiometric purity through enzymatic enantioselective transesterificaion in organic media. To achieve this, immobilization of the lipase and the effects of different reaction conditions (e.g. organic solvent, water activity, substrate ratio and temperature) on the activity and enantioselectivity of the lipase were investigated. RESULTS Lipase from Alcaligenes sp. (lipase QL) was successfully immobilized onto the prepared magnetic Fe3O4 nanoparticles through hydrophobic interaction, and the enzyme loading (97.4 ± 2.3 mg g−1) as well as immobilization yield (48.7 ± 1.4%) was obtained. Under optimum reaction conditions, the higher enzyme activity (0.225 ± 0.01 µmol mg−1 min−1) and enantioselectivity (E-value: 59.7 ± 1.8) for the immobilized lipase QL than those (enzyme activity: 0.034 ± 0.002 µmol mg−1 min−1, E-value: 57.9 ± 2.0) for aggregated lipase was observed. The results also showed that (S)-2-(2-chloro-1-hydroxyethyl) thiophene with optical purity ≥99% was obtained. In addition, the immobilized lipase QL was easily separated from the reaction media by magnetic steel, and maintained 90% of its initial activity with nearly unchanged enantioselectivity after five consecutive cycles. CONCLUSION The results obtained demonstrated good potential for practical application of magnetic nanoparticle-immobilized lipase for the resolution of 2-(2-chloro-1-hydroxyethyl) thiophene through enantioselective transesterification. © 2014 Society of Chemical Industry
- Published
- 2014
6. Resolution ofN-hydroxymethyl vince lactam catalyzed by lipase in organic solvent
- Author
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Lei Wang, Hong Yue, Ge Chen, Jiaxin Wang, Erna Xun, Zhi Wang, Hong Zhang, and Jimin Zhao
- Subjects
chemistry.chemical_classification ,biology ,Renewable Energy, Sustainability and the Environment ,organic chemicals ,General Chemical Engineering ,Organic Chemistry ,Enantioselective synthesis ,Substrate (chemistry) ,Transesterification ,Valerate ,Pollution ,Inorganic Chemistry ,chemistry.chemical_compound ,Fuel Technology ,chemistry ,polycyclic compounds ,biology.protein ,Organic chemistry ,heterocyclic compounds ,Hydroxymethyl ,Lipase ,Enantiomer ,Waste Management and Disposal ,Vince lactam ,Biotechnology - Abstract
BACKGROUND: The enantiomers of N-hydroxymethyl vince lactam are important intermediates during the synthesis of chiral drugs. The preparation of its single enantiomer can be performed through enzymatic resolution. The aim of this work is to obtain (1S ,4 R)-N-hydroxymethyl vince lactam with high enantiomeric purity via lipase-catalyzed enantioselective transesterification in organic solvents. To achieve this, effects of various reaction conditions (including lipase sources, acyl donor, substrate molar ratio, organic solvent, temperature, and water activity) on the enzyme activity as well as enantioselectivity were investigated. RESULTS: The results of the study showed that the enantiopreference for all the selected enzymes was (4S ,1 R)-N-hydroxymethyl vince lactam in enantioselective transesterification of racemic N-hydroxymethyl vince lactam. Under the selected optimum conditions, the highest enantioselectivity (E = 33.8) was obtained with a higher enzyme activity (20.3 µmol g −1 min −1 )f or Mucor miehei lipase (MML) when vinyl valerate was used as the acyl donor. Besides, the remained (1S ,4 R)-N-hydroxymethyl vince lactam with high enantiomeric purity (ee > 99%) was obtained when the conversion was about 60%. CONCLUSION: The results obtained clearly demonstrated potential for industrial application of lipase in resolution of N-hydroxymethyl vince lactam through enantioselective transesterification. c � 2012 Society of Chemical Industry
- Published
- 2012
7. Synthesis of Triptorelin Lactate Catalyzed by Lipase in Organic Media
- Author
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Ge Chen, Hong Zhuang, Ning Tang, Zhi Wang, Lei Wang, Hong Zhang, Jiaxin Wang, Erna Xun, and Hong Yue
- Subjects
Water activity ,Swine ,Kinetics ,triptorelin lactate ,Article ,Catalysis ,Inorganic Chemistry ,lcsh:Chemistry ,Organic chemistry ,Animals ,Physical and Theoretical Chemistry ,Lipase ,Organic Chemicals ,Molecular Biology ,lcsh:QH301-705.5 ,Spectroscopy ,Triptorelin Pamoate ,biology ,Bacteria ,Esterification ,Chemistry ,Organic Chemistry ,Temperature ,Substrate (chemistry) ,Water ,General Medicine ,Hydrogen-Ion Concentration ,Enzyme assay ,Computer Science Applications ,enzyme activity ,lcsh:Biology (General) ,lcsh:QD1-999 ,Yield (chemistry) ,biology.protein ,Lactates ,Solvents ,Triptorelin lactate - Abstract
Triptorelin lactate was successfully synthesized by porcine pancreatic lipase (PPL) in organic solvents. The effects of acyl donor, substrate ratio, organic solvent, temperature, and water activity were investigated. Under the optimum conditions, a yield of 30% for its ester could be achieved in the reaction for about 48 h.
- Published
- 2012
8. Potential for pH Monitoring the Enzyme-Catalyzed Hydrolysis of Esters with a Novel Nano-Engineered Fluorescent Probe
- Author
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Jiaxin Wang, Zhi Wang, Shigang Wei, Erna Xun, Yanfu Huan, and Lina Xue
- Subjects
Hydrolysis ,Enzyme catalyzed ,Chemistry ,Nano ,Electrical and Electronic Engineering ,Combinatorial chemistry ,Fluorescence ,Ph monitoring ,Atomic and Molecular Physics, and Optics - Published
- 2012
9. Optimization of APE1547-catalyzed enantioselective transesterification of (R/S)-2-methyl-1-butanol in an ionic liquid
- Author
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Xiao-Fei Wei, Ren Wang, Rui Tian, Zhi Wang, Shugui Cao, Erna Xun, Chun-Hua Yang, and Lei Wang
- Subjects
Water activity ,biology ,Biomedical Engineering ,Enantioselective synthesis ,Substrate (chemistry) ,Bioengineering ,Transesterification ,biology.organism_classification ,Applied Microbiology and Biotechnology ,Esterase ,Catalysis ,chemistry.chemical_compound ,chemistry ,Ionic liquid ,Organic chemistry ,Aeropyrum pernix ,Biotechnology - Abstract
Aeropyrum pernix esterase (APE1547) was successfully used to catalyze the enantioselective transesterification of (R/S)-2-methyl-1-butanol in an ionic liquid (IL). Effects of various reaction conditions on the synthetic activity of the enzyme as well as enantioselectivity, including the type of IL, acyl donor, temperature, water activity, and substrate molar ratio were inverstigated. APE1547 showed good catalytic performance (activity > 0.8 μmol/min/mg, E > 25), and the enzyme-IL mixture was recycled five times with only a slight decrease in catalytic performance.
- Published
- 2011
10. Immobilization of Pseudomonas fluorescens lipase onto magnetic nanoparticles for resolution of 2-octanol
- Author
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Wei Kang, Jiaxin Wang, Zhi Wang, Hong Zhang, Erna Xun, Lei Wang, and Xiao-li Lv
- Subjects
2-Octanol ,Octanols ,Water activity ,Bioengineering ,Pseudomonas fluorescens ,Applied Microbiology and Biotechnology ,Biochemistry ,Hydrophobic effect ,chemistry.chemical_compound ,Vinyl acetate ,Lipase ,Magnetite Nanoparticles ,Molecular Biology ,Chromatography ,biology ,Hydrolysis ,Temperature ,Substrate (chemistry) ,Stereoisomerism ,General Medicine ,biology.organism_classification ,Enzymes, Immobilized ,chemistry ,Yield (chemistry) ,biology.protein ,Biotechnology - Abstract
The lipase from Pseudomonas fluorescens (Lipase AK, AKL) was immobilized onto the magnetic Fe3O4 nanoparticles via hydrophobic interaction. Enzyme loading and immobilization yield were determined as 21.4 ± 0.5 mg/g and 49.2 ± 1.8 %, respectively. The immobilized AKL was successfully used for resolution of 2-octanol with vinyl acetate used as acyl donor. Effects of organic solvent, water activity, substrate ratio, and temperature were investigated. Under the optimum conditions, the preferred isomer for AKL is the (R)-2-octanol and the highest enantioselectivity (E = 71.5 ± 2.2) was obtained with a higher enzyme activity (0.197 ± 0.01 μmol/mg/min). The results also showed that the immobilized lipase could be easily separated from reaction media by the magnetic steel and remained 89 % of its initial activity as well as the nearly unchanged enantioselectivity after five consecutive cycles, indicating a high stability in practical operation.
- Published
- 2011
11. Immobilization of Laccase for Oxidative Coupling of Trans-Resveratrol and Its Derivatives.
- Author
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Hong Zhang, Erna Xun, Jiaxin Wang, Ge Chen, Tiexin Cheng, Zhi Wang, Tengfei Ji, and Lei Wang
- Subjects
- *
OXIDATIVE stress , *RESVERATROL , *DRUG derivatives , *LACCASE , *ENZYME activation , *IMMOBILIZED enzymes - Abstract
Trametes villosa Laccase (TVL) was immobilized through physical adsorption on SBA-15 mesoporous silica and the immobilized TVL was used in the oxidative coupling of trans-resveratrol. Higher loading and activity of the immobilized enzyme on SBA-15 were obtained when compared with the free enzyme. The effects of reaction conditions, such as buffer type, pH, temperature and substrate concentration were investigated, and the optimum conditions were screened and resulted in enzyme activity of up to 10.3 µmol/g·h. Furthermore, the oxidative couplings of the derivatives of trans-resveratrol were also catalyzed by immobilized TVL. The immobilized TVL was recyclable and could maintain 78% of its initial activity after reusing it four times. [ABSTRACT FROM AUTHOR]
- Published
- 2012
- Full Text
- View/download PDF
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