Documents disponibles écrits par cet auteur

Asymmetric Aldol Addition by oligopeptide immobilized on magnetic particles through an lonic liquids spacer / Yangyang Jiang in Industrial & engineering chemistry research, Vol. 47 N° 23 (Décembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9628–9635 Titre : Asymmetric Aldol Addition by oligopeptide immobilized on magnetic particles through an lonic liquids spacer Type de document : texte imprimé Auteurs : Yangyang Jiang, Auteur ; Chen, Guo, Auteur ; Hansong Xia, Auteur Année de publication : 2009 Article en page(s) : p. 9628–9635 Note générale : Chemistry engineering Langues : Anglais (eng) Mots-clés : Oligopeptide  Magnetic  particles  Ionic  liquids  spacer Résumé : In this work, oligopeptide was covalently bonded on the surface of magnetic particles through an ionic liquids spacer. When ionic liquids containing bulky cations with strong H-bonding ability or having hydrophobic anions were used, the yield and enantioselectivity of aldol reaction were enhanced greatly. Introducing an ionic liquids spacer between the oligopeptide and magnetic resin decreased the minimum number of amino acids for optimizing the efficiency of aldol addition. Varying the amino acid sequence of the oligopeptide showed limited effect on the yield and enantioselectivity; however, introducing a series of lysine groups on the terminal of the oligopeptide, close to the imidazolium ring, would significantly increase the output. The magnetite-loaded oligopeptide had a broader substrate range for ketone donor but restricted the enantioselectivity of aldehyde acceptor than the free oligopeptide. The combinative unit served as a recyclable catalyst for aldol addition of ketone and aldehyde, and its catalytic efficiency and selectivity can be finely designed by the characteristics of each part of the catalyst. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0712131 [article] Asymmetric Aldol Addition by oligopeptide immobilized on magnetic particles through an lonic liquids spacer [texte imprimé] / Yangyang Jiang, Auteur ; Chen, Guo, Auteur ; Hansong Xia, Auteur . - 2009 . - p. 9628–9635. Chemistry engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N° 23 (Décembre 2008) . - p. 9628–9635 Mots-clés : Oligopeptide  Magnetic  particles  Ionic  liquids  spacer Résumé : In this work, oligopeptide was covalently bonded on the surface of magnetic particles through an ionic liquids spacer. When ionic liquids containing bulky cations with strong H-bonding ability or having hydrophobic anions were used, the yield and enantioselectivity of aldol reaction were enhanced greatly. Introducing an ionic liquids spacer between the oligopeptide and magnetic resin decreased the minimum number of amino acids for optimizing the efficiency of aldol addition. Varying the amino acid sequence of the oligopeptide showed limited effect on the yield and enantioselectivity; however, introducing a series of lysine groups on the terminal of the oligopeptide, close to the imidazolium ring, would significantly increase the output. The magnetite-loaded oligopeptide had a broader substrate range for ketone donor but restricted the enantioselectivity of aldehyde acceptor than the free oligopeptide. The combinative unit served as a recyclable catalyst for aldol addition of ketone and aldehyde, and its catalytic efficiency and selectivity can be finely designed by the characteristics of each part of the catalyst. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie0712131

Lipase immobilization on oleic acid-pluronic (L-64) block copolymer coated magnetic nanoparticles, for hydrolysis at the oil/water interface / Iram Mahmood in Industrial & engineering chemistry research, Vol. 47 N°17 (Septembre 2008) 

Public ISBD [article]  in Industrial & engineering chemistry research > Vol. 47 N°17 (Septembre 2008) . - p. 6379–6385 Titre : Lipase immobilization on oleic acid-pluronic (L-64) block copolymer coated magnetic nanoparticles, for hydrolysis at the oil/water interface Type de document : texte imprimé Auteurs : Iram Mahmood, Auteur ; Chen, Guo, Auteur ; Hansong Xia, Auteur Année de publication : 2008 Article en page(s) : p. 6379–6385 Note générale : Chemical engineering Langues : Anglais (eng) Mots-clés : Iron  oxide  nanoparticles  Oleic  acid  Pluronic  Transmission  electron  microscopy  X-ray  diffraction Résumé : Here, we have reported a new approach for utilizing oleic acid−Pluronic L-64 block copolymer coated iron oxide nanoparticles as supports for enzyme immobilization. Iron oxide nanoparticles were prepared by a coprecipitation method and were coated with oleic acid and Pluronic to achieve higher stability and dispersibility. The surface morphology and size of the particle, as determined by transmission electron microscopy (TEM), was ±10 nm. X-ray diffraction (XRD) patterns were taken over a range from 10° to 90° 2θ, using Cu Kα radiation. Saturation magnetization values, measured at 300 K, varied from 34.6 emu/g to 60.8 emu/g. The possible interaction behavior of oleic acid and Pluronic was observed by Fourier transform infrared (FTIR) analysis and nuclear magnetic resonance (NMR) studies. Further potential of this material as a support for lipase immobilization and enzymatic hydrolysis at the oil/water interface was also investigated. The features of the surface-coated magnetic particles enable the adsorption of lipase from Candida cylindraces via strong hydrophobic interactions, which enhances the stability of the adsorbed enzyme molecules. The stability of the catalyst and, hence, its industrial applicability was tested by performing subsequent reaction cycles for the hydrolysis of olive oil. The activity of the immobilized lipase, pretreated with its substrate, was 510 U/g-matrix and was observed to be maintained at levels as high as 90% of its original activity for up to at least seven reuses. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie701788x [article] Lipase immobilization on oleic acid-pluronic (L-64) block copolymer coated magnetic nanoparticles, for hydrolysis at the oil/water interface [texte imprimé] / Iram Mahmood, Auteur ; Chen, Guo, Auteur ; Hansong Xia, Auteur . - 2008 . - p. 6379–6385. Chemical engineering Langues : Anglais (eng) in Industrial & engineering chemistry research > Vol. 47 N°17 (Septembre 2008) . - p. 6379–6385 Mots-clés : Iron  oxide  nanoparticles  Oleic  acid  Pluronic  Transmission  electron  microscopy  X-ray  diffraction Résumé : Here, we have reported a new approach for utilizing oleic acid−Pluronic L-64 block copolymer coated iron oxide nanoparticles as supports for enzyme immobilization. Iron oxide nanoparticles were prepared by a coprecipitation method and were coated with oleic acid and Pluronic to achieve higher stability and dispersibility. The surface morphology and size of the particle, as determined by transmission electron microscopy (TEM), was ±10 nm. X-ray diffraction (XRD) patterns were taken over a range from 10° to 90° 2θ, using Cu Kα radiation. Saturation magnetization values, measured at 300 K, varied from 34.6 emu/g to 60.8 emu/g. The possible interaction behavior of oleic acid and Pluronic was observed by Fourier transform infrared (FTIR) analysis and nuclear magnetic resonance (NMR) studies. Further potential of this material as a support for lipase immobilization and enzymatic hydrolysis at the oil/water interface was also investigated. The features of the surface-coated magnetic particles enable the adsorption of lipase from Candida cylindraces via strong hydrophobic interactions, which enhances the stability of the adsorbed enzyme molecules. The stability of the catalyst and, hence, its industrial applicability was tested by performing subsequent reaction cycles for the hydrolysis of olive oil. The activity of the immobilized lipase, pretreated with its substrate, was 510 U/g-matrix and was observed to be maintained at levels as high as 90% of its original activity for up to at least seven reuses. En ligne : http://pubs.acs.org/doi/abs/10.1021/ie701788x