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  • 1.
    Branneby, Cecilia
    et al.
    KTH, Superseded Departments, Biotechnology.
    Carlqvist, Peter
    KTH, Superseded Departments, Chemistry.
    Hult, Karl
    KTH, Superseded Departments, Biotechnology.
    Brinck, Tore
    KTH, Superseded Departments, Chemistry.
    Berglund, Per
    KTH, Superseded Departments, Biotechnology.
    Aldol Additions with Mutant Lipase: Analysis by Experiments and Theoretical Calculations2004In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 31, no 4-6, p. 123-128Article in journal (Refereed)
    Abstract [en]

    A Ser105Ala mutant of Candida antarctica lipase B has previously been shown to catalyze aldol additions. Quantum chemical calculations predicted a reaction rate similar to that of natural enzymes, whereas experiments showed a much lower reaction rate. Molecular dynamics simulations, presented here, show that the low reaction rate is a consequence of the low frequencies of near attack complexes in the enzyme. Equilibrium was also considered as a reason for the slow product formation, but could be excluded by performing a sequential reaction to push the reaction towards product formation. In this paper, further experimental results are also presented, highlighting the importance of the entire active site for catalysis.

  • 2.
    Chen, Shan
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Land, Henrik
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Svedendahl Humble, Maria
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Stabilization of an amine transaminase for biocatalysis2016In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 124, p. 20-28Article in journal (Refereed)
    Abstract [en]

    The amine transaminase from Chromobacterium violaceum (Cv-ATA) is a well-known enzyme to achievechiral amines of high enantiomeric excess in laboratory scales. However, the low operational stabilityof Cv-ATA limits the enzyme applicability on larger scales. In order to improve the operational stabilityof Cv-ATA, and thereby extending its applicability, factors (additives, co-solvents, organic solvents anddifferent temperatures) targeting enzyme stability and activity were explored in order to find out how tostore and apply the enzyme. The present investigation shows that the melting point of Cv-ATA is improvedby adding sucrose or glycerol, separately. Further, by storing the enzyme at higher concentrations and inco-solvents, such as; 50% glycerol, 20% methanol or 10% DMSO, the active dimeric structure of Cv-ATAis retained. Enzyme stored in 50% glycerol at −20◦C was e.g., still fully active after 6 months. Finally,the enzyme performance was improved 5-fold by a co-lyophilization with surfactants prior to usage inisooctane.

  • 3. Gaffney, Darragh
    et al.
    Abdallah, Noreldeen H.
    Cooney, Jakki C.
    Laffir, Fathima R.
    Engelmark Cassimjee, Karim
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Berglund, Per
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Hanefeld, Ulf
    Magner, Edmond
    Preparation and characterisation of a Ni2+/Co2+-cyclam modified mesoporous cellular foam for the specific immobilisation of His(6)-alanine racemase2014In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 109, p. 154-160Article in journal (Refereed)
    Abstract [en]

    Nickel and cobalt cyclam modified mesocellular foam (MCF) materials were prepared and characterised. The metal cyclam modified materials displayed reduced surface areas and pore diameters in comparison to MCF. The modified materials were used to specifically anchor a histidine tagged form of the enzyme, alanine racemase (HT-AlaR). Non-specific adsorption was predominantly hydrophobic//hydrophilic in nature and could be significantly reduced in the presence of 2% polyethylene glycol. The activity of HT-AlaR immobilised on Ni and Co-MCF was essentially the same as that of the free enzyme, demonstrating that enzymes can be specifically immobilised within the pores of mesoporous materials in a stable and catalytically active manner.

  • 4.
    Hedfors, Cecilia
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry.
    Hult, Karl
    KTH, School of Biotechnology (BIO), Biochemistry.
    Martinelle, Mats
    KTH, School of Biotechnology (BIO), Biochemistry.
    Lipase chemoselectivity towards alcohol and thiol acyl acceptors in a transacylation reaction2010In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 66, no 1-2, p. 120-123Article in journal (Refereed)
    Abstract [en]

    The lipase chemoselectivity towards an alcohol and a thiol was investigated for the two lipases Candida antarctica lipase B (CalB) and Rhizomucor miehei lipase (Rml). Hexanol and hexanethiol were used as acyl acceptors in a transacylation reaction with ethyl octanoate in cyclohexane. CalB showed the highest chemoselectivity ratio (k(cat)/K-M)(OH)/(k(cat)/K-M)(SH), of 88,000 while the ratio for Rml was 1200. That could be compared with the ratio, k(OH)/k(SH), of 120 for the non-catalyzed reaction. Thus, the enzyme contribution to the chemoselectivity between hexanol and hexanethiol was 730 for CalB and 10 for Rml. High K-M values displayed towards hexanethiol (above 1.8 M) were the largest contribution to the selectivity. No saturation was achieved. The K-M values were more than two orders of magnitude higher than those of hexanol.

  • 5.
    Isaksson, Dan
    et al.
    KTH, Superseded Departments, Chemistry.
    Lindmark-Henriksson, Marcia
    KTH, Superseded Departments, Chemistry.
    Manoranjan, T
    Sjödin, Kristina
    KTH, Superseded Departments, Chemistry.
    Högberg, Hans-Erik
    KTH, Superseded Departments, Chemistry.
    Hemiacetals and their esters as side-products in lipase-catalysed transesterifications of vinyl esters with sterically hindered alcohols2004In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 31, p. 31-37Article in journal (Refereed)
    Abstract [en]

    Lipase-catalysed transesterifications of vinyl esters with various sterically hindered secondary alcohols sometimes give hemiacetals and hemiacetal esters as major side-products along with the expected esters, especially in the presence of aldehydes. The substrates, reaction conditions, and the lipases required for the formation of such hemiacetal products have been studied. Hemiacetals and their esters are very easily hydrolysed. Therefore, when conventional work-up procedures are used, the formation of such products in lipase-catalysed transesterification reactions may easily escape notice, leading to, e.g. an unexpectedly low enantiomeric purity of the isolated remaining substrate in a resolution reaction.

  • 6. Ivanova, Ekaterina V.
    et al.
    Kurnikov, Igor V.
    Fischer, Andreas
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Inorganic Chemistry.
    Alexandrova, Larissa
    Ryabov, Alexander D.
    Enantio selectivity of resolved Delta and Lambda orthoruthenated 2-phenylpyridine complexes Ru(o-C6H4-2-py)(LL)(2) PF6 (LL = bpy and phen) toward glucose oxidase2006In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 41, no 04-mar, p. 110-116Article in journal (Refereed)
    Abstract [en]

    Cyclometalated 2-phenylpyridine complexes [Ru-II(o-C6H4-2-py)(LL)(2)]PF6, LL=2,2'-bipyridine (1) and 1,10-phenanthroline (2) were resolved into A and A enantiomers using column chromatography on SP Sephadex C-25 in the presence of (+)-2,3-dibenzoyl-D-tartrate. The absolute configuration of enantiomers was established using circular dichroism spectroscopy. The rate constants k(et) for the electron transfer from reduced glucose oxidase (GO from Aspergillus niger) and PQQ-dependent glucose dehydrogenase (GDH) at the generated Ru-III species were measured by cyclic voltammetry and UV-vis spectroscopy. The electron transfer shows enantioselectivity. In the case of GO, the bell-shaped pH profile for the ratio k(Lambda)/k(Delta) has a maximum at pH 7 (k(Lambda)/k(Delta) equals 3.4 and 3.9 for 1 and 2, respectively), but its inversion is observed at pH around 5 and 9. The k(Lambda)/k(Delta) ratio equals 2.0 for 2 and GDH at pH 7. The results of theoretical modeling of biological electron transfer for GO using functional docking Monte-Carlo simulations are presented and analyzed together with the experimental observations.

  • 7. Leonard-Nevers, Valerie
    et al.
    Marton, Zsuzsanna
    Lamare, Sylvain
    Hult, Karl
    KTH, School of Biotechnology (BIO), Biochemistry.
    Graber, Marianne
    Understanding water effect on Candida antarctica lipase B activity and enantioselectivity towards secondary alcohols2009In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 59, no 1-3, p. 90-95Article in journal (Refereed)
    Abstract [en]

    The effect of water activity (a(w)) on Candida antarctica lipase B (CALB) activity and enantioselectivity towards secondary alcohols was assessed. Experimental results for the resolution of racemic pentan-2-ol, hexan-3-ol, butan-2-ol and octan-4-ol by immobilized CALB-catalyzed acylation with methyl propanoate were obtained by using a solid/gas reactor. Water and substrate adsorption mechanism on immobilized CALB were then studied using moisture sorption analyzer and inverse gas chromatography, and the effective hydration state of the biocatalyst when varying aw was defined. The data showed a pronounced aw effect on both activity and enantioselectivity. If secondary alcohol follows the steric rules for being efficiently resolved, water at very low aw increased enantioselectivity by acting predominantly as an enantioselective inhibitor, making the stereospecificity pocket smaller. When increasing aw, water decreased enantioselectivity, due to an unfavourable increase of the entropic term T Delta(R-S)Delta S-double dagger of the differential free energy of activation. The "turning point" at which water changed from one predominant role to another would correspond to aw allowing full coverage of polar groups of the immobilized biocatalyst by water molecules.

  • 8. Marton, Z.
    et al.
    Leonard-Nevers, V.
    Syrén, Per-Olof
    KTH, School of Biotechnology (BIO), Biochemistry.
    Bauer, C.
    Lamare, S.
    Hult, Karl
    KTH, School of Biotechnology (BIO), Biochemistry.
    Tranc, V.
    Graber, M.
    Mutations in the stereospecificity pocket and at the entrance of the active site of Candida antarctica lipase B enhancing enzyme enantioselectivity2010In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 65, no 1-4, p. 11-17Article in journal (Refereed)
    Abstract [en]

    Two different parts of Candida antarctica lipase B (stereospecificity pocket at the bottom of the active site and hydrophobic tunnel leading to the active site) were redesigned by single- or double-point mutations, in order to better control and improve enzyme enantioselectivity toward secondary alcohols. Single-point isosteric mutations of Ser47 and Thr42 situated in the stereospecificity pocket gave rise to variants with doubled enantioselectivity toward pentan-2-ol, in solid/gas reactor. Besides, the width and shape of the hydrophobic tunnel leading to the active site was modified by producing the following single-point mutants: Ile189Ala, Leu278Val and Ala282Leu. For each of these variants a significant modification of enantioselectivity was observed compared to wild-type enzyme, indicating that discrimination of the enantiomers by the enzyme could also arise from their different accessibilities from the enzyme surface to the catalytic site. (C) 2010 Elsevier B.V. All rights reserved.

  • 9. Naik, Sangeeta
    et al.
    Basu, Aditya
    Saikia, Rakhi
    Madan, Bhawna
    Paul, Pritish
    Chaterjee, Robin
    KTH, School of Biotechnology (BIO), Biochemistry.
    Brask, Jesper
    Svendsen, Allan
    Lipases for use in industrial biocatalysis: Specificity of selected structural groups of lipases2010In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 65, no 1-4, p. 18-23Article in journal (Refereed)
    Abstract [en]

    Lipases for biocatalysis The substrate specificity of a selected group of lipases was investigated. The enzymes selected were from four structural groups. Group 1: lipases having wide alcohol binding cleft but a narrow acyl binding cleft (Rhizomucor miehei lipase. Thermomyces lanuginosus lipase. Fusarium oxysporum lipase); Group 2: lipases which exhibit strong restriction on the acid part having a narrow tunnel to accommodate the acyl group but wider alcohol binding site (Candida antarctica A, Candida rugosa lipase); Group 3: lipases having wide acyl binding cleft but narrow alcohol binding cleft (C. antarctica lipase B, Ustilago maydis lipase), and Group 4: having wider alcohol and wider acyl binding clefts (Fusarium solani pisi cutinase, Humicola insolens cutinase). Owing to the wide substrate specificity and higher expression levels in recombinant host, these lipases have tremendous importance for hydrolysis and synthesis reactions. Various substrates with substitutions on the alcohol and/or the acid part of the ester molecule were selected. The experimental results support the classification of lipases on the basis of their binding sites. For substrates with heavy alcohol side, C. Antarctica lipase A and R. miehei lipase type enzymes gave the highest extent of hydrolysis, while for acid heavy substrates the highest conversions were shown by C. antarctica lipase B. It is noteworthy that the acid heavy substrates which had aromatic side chains were hydrolyzed only by C. antarctica lipase B type of enzymes. Lipases were found to be more active on the alcohol-substituted substrates than acid-substituted substrates. (C) 2010 Elsevier B.V. All rights reserved.

  • 10.
    Ottosson, Jenny
    et al.
    KTH, Superseded Departments, Biotechnology.
    Hult, Karl
    KTH, Superseded Departments, Biotechnology.
    Influence of acyl chain length on the enantioselectivity of Candida antarctica lipase B and its thermodynamic components in kinetic resolution of sec-alcohols2001In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 11, no 4-6, p. 1025-1028Article in journal (Refereed)
    Abstract [en]

    The enantioselectivity, E, of Candida antarctica lipase B (CALB) was found to be strongly influenced by the chain length of the achiral acyl donor employed in the transesterification of 3-methyl-2-butanol. Of the four studied acyl donors, the longest, vinyl octanoate, afforded the highest enantioselectivity. This was true over the temperature range studied, 6-70 degreesC. Measurements of the temperature dependence of E allows for separation of the enthalpic and entropic components of enantioselectivity. Changes in E with chain length were mainly caused by changes in the entropic component except for the reaction with vinyl propionate, which differed from the others also in the enthalpic component. Optimisation of acyl donor adds one more possibility to improve the yield of enantiopurity in the production of optically active compounds apart from optimisation of solvent, temperature, water activity, and choice of enzyme.

  • 11.
    Syren, Per-Olof
    et al.
    KTH, School of Biotechnology (BIO), Biochemistry. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Lindgren, Ebba
    KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Hoeffken, Hans Wolfgang
    Branneby, Cecilia
    Maurer, Steffen
    Hauer, Bernhard
    Hult, Karl
    KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, School of Biotechnology (BIO), Biochemistry.
    Increased activity of enzymatic transacylation of acrylates through rational design of lipases2010In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 65, no 1-4, p. 3-10Article in journal (Refereed)
    Abstract [en]

    A rational design approach was used to create the mutant Candida antarctica lipase B (CALB, also known as Pseudozyma antarctica lipase B) V190A having a k(cat) three times higher compared to that of the wild type (wt) enzyme for the transacylation of the industrially important compound methyl methacrylate. The enzymatic contribution to the transacylation of various acrylates and corresponding saturated esters was evaluated by comparing the reaction catalysed by CALB wt with the acid (H2SO4) catalysed reaction. The performances of CALB wt and mutants were compared to two other hydrolases, Humicola insolens cutinase and Rhizomucor mihei lipase. The low reaction rates of enzyme catalysed transacylation of acrylates were found to be caused mainly by electronic effects due to the double bond present in this class of molecules. The reduction in rate of enzyme catalysed transacylation of acrylates compared to that of the saturated ester methyl propionate was however less than what could be predicted from the energetic cost of breaking the pi-system of acrylates solely. The nature and concentration of the acyl acceptor was found to have a profound effect on the reaction rate. (C) 2009 Elsevier B.V. All rights reserved.

  • 12. Vallikivi, I.
    et al.
    Fransson, Linda
    KTH, School of Biotechnology (BIO), Biochemistry.
    Hult, Karl
    KTH, School of Biotechnology (BIO), Biochemistry.
    Järving, I.
    Pehk, T.
    Samel, N.
    Tougu, V.
    Villo, L.
    Parve, O.
    The modelling and kinetic investigation of the lipase-catalysed acetylation of stereoisomeric prostaglandins2005In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 35, no 1-3, p. 62-69Article in journal (Refereed)
    Abstract [en]

    The lipase-catalysed acetylation of the hydroxyl groups of five stereoisomeric prostaglandins of type F was investigated by means of molecular dynamics simulations and the results compared with experimental observations. An NMR spectroscopic monitoring was performed to estimate reaction velocities and the regioselectivity. A molecular modelling protocol that could qualitatively differentiate between the OH groups of prostaglandins being either accessible or unaccessible to the Candida antarctica lipase B (CALB) catalysed acetylation was developed. The protocol developed analysed the protein structure deformation, the content of essential hydrogen bonds and the function-based subset energy of tetrahedral intermediates along the molecular dynamics simulations trajectory. The tetrahedral intermediates displaying a deformation RMS value lower than 3.0 angstrom, an essential hydrogen bond content over 50% and a subset energy less than -95 kJ/mol were classified active. In total, the accessibility of 16 out of 17 different prostaglandin OH groups was correctly predicted.

  • 13.
    Viklund, Fredrik
    et al.
    KTH, Superseded Departments, Biotechnology.
    Hult, Karl
    KTH, Superseded Departments, Biotechnology.
    Enzymatic synthesis of surfactants based on polyethylene glycol and stearic or 12-hydroxystearic acid2004In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 27, no 2-3, p. 51-53Article in journal (Refereed)
    Abstract [en]

    High-purity mono- and di-esters of polyethylene glycol (molecular weight: 600) with stearic acid or 12-hydroxystearic acid was afforded using enzymatic catalysis with immobilized Candida antarctica lipase B. The reactions were performed without solvent and the formed water was removed with vacuum, driving the reactions to completion. Isolated yields varied between 77 and 87%.

  • 14.
    Zhang, Yan
    et al.
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Zhang, Yang
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ren, Yansong
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Ramström, Olof
    KTH, School of Chemical Science and Engineering (CHE), Chemistry, Organic Chemistry.
    Synthesis of chiral oxazolidinone derivatives through lipase-catalyzed kinetic resolution2015In: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 122, p. 29-34Article in journal (Refereed)
    Abstract [en]

    The synthesis of enantioenriched oxazolidinone derivatives through lipase-catalyzed kinetic resolution is described. The synthesis comprised a two-step, cascade acylation in one pot, resulting in a range of oxazolidinone derivatives in good yields and excellent enantiopurities.

1 - 14 of 14
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