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  • 1.
    Berglund, Per
    et al.
    KTH, Tidigare Institutioner, Bioteknologi.
    Vallikivi, I.
    Fransson, Linda
    KTH, Tidigare Institutioner, Bioteknologi.
    Dannacher, H.
    Holmquist, Mats
    KTH, Tidigare Institutioner, Bioteknologi.
    Martinelle, Mats
    KTH, Tidigare Institutioner, Bioteknologi.
    Björkling, F.
    Parve, O.
    Hult, Karl
    KTH, Tidigare Institutioner, Bioteknologi.
    Switched enantiopreference of Humicola lipase for 2-phenoxyalkanoic acid ester homologs can be rationalized by different substrate binding modes1999Ingår i: Tetrahedron: asymmetry, ISSN 0957-4166, E-ISSN 1362-511X, Vol. 10, nr 21, s. 4191-4202Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Humicola lanuginosa lipase was used for enantioselective hydrolyses of a series of homologous 2-phenoxyalkanoic acid ethyl esters. The enantioselectivity (E-value) of the enzyme changed from an (R)-enantiomer preference for the smallest substrate, 2-phenoxypropanoic acid ester, to an (S)-enantiomer preference for the homologous esters with longer acyl moieties. The E-values span the range from E=13 (R) to E=56 (S). A molecular modeling study identified two different substrate-binding modes for each enantiomer. We found that the enantiomers favored different modes. This discovery provided a model that offered a rational explanation for the observed switch in enantioselectivity. (C) 1999 Elsevier Science Ltd. All rights reserved.

  • 2.
    Fransson, Linda
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Enzyme substrate solvent interactions: a case study on serine hydrolases2008Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Reaction rates and selectivities were measured for transacylation of fatty acid esters in solvents catalysed by Candida antarctica lipase B and by cutinase from Humicola insolens. With these enzymes classical water-based enzymology can be expanded to many different solvents allowing large variations in interaction energies between the enzymes, the substrates and the surrounding. Further ,hydrolysis reactions catalysed by Bacillus subtilis esterase 2 were investigated.

    Thermodynamics analyses revealed that the enzyme contribution to reaction rate acceleration compared to acid catalysis was purely entropic. On the other hand, studies of differences in activation entropy and enthalpy between enantiomers and between homologous esters showed that high substrate specificity was favoured by enthalpic stabilisation.

    Solvent was found to have a profound effect on enzyme catalysis, affecting both reaction rate and selectivity. Differences in substrate solubility will impact enzyme specificity since substrate binding is an equilibrium between enzyme-bound substrate and substrate in free solution. In addition, solven tmolecules were found to act as enzyme inhibitors, showing both competitive and non-competitive behaviour.

    In several homologous data series enthalpy-entropy compensation relationships were encountered. A possible extrathermodynamic relationship between enthalpy and entropy can easily be lost under co-varying errors propagated from the experiments. From the data in this thesis, one instance was found of a real enthalpy-entropy compensation that could be distinguished from statistical errors, while other examples could not be verified.

  • 3.
    Fransson, Linda
    KTH, Skolan för bioteknologi (BIO).
    Molecular modelling - understanding and prediction of enzyme selectivity.2009Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Molecular modelling strategies for evaluation of enzyme selectivity wereinvestigated with a focus on principles of how molecular interactionscould be evaluated to provide information about selectivity. Althoughmolecular modelling provides tools for evaluation of geometrical andenergy features of molecular systems, no general strategies for evaluationof enzyme selectivity exist. Geometrical analyses can be based uponinspection and reasoning about molecular interactions, which provide aneasily accessible way to gain information, but suffer from the risk of biasput in by the modeller. They can also be based on geometrical features ofmolecular interactions such as bond lengths and hydrogen-bond formation.Energy analyses are appealing for their modeller independenceand for the possibility to predict not only stereopreference, but also itsmagnitude.In this thesis, four examples of enantio- or regioselective serinehydrolase-catalysed reaction systems are presented together with developedmodelling protocols for explanation, prediction or enhancement ofselectivity. Geometrical as well as energy-based methodology were used,and provided an understanding of the structural basis of enzymeselectivity. In total, the protocols were successful in making qualitative explanationsand predictions of stereoselectivity, although quantitative determinationswere not achieved.

  • 4.
    Fransson, Linda
    et al.
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Bernhardt, Peter
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Hult, Karl
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    On the benefit of an active siteManuskript (preprint) (Övrigt vetenskapligt)
  • 5.
    Fransson, Linda
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi. KTH, Skolan för bioteknologi (BIO), Biokemi. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Laurell, Anna
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Widyan, Khalid
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Wingstrand, Erica
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Hult, Karl
    KTH, Skolan för bioteknologi (BIO), Biokemi. KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Moberg, Christina
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Minor Enantiomer Recycling-Effect of Two Reinforcing Catalysts on Product Yield and Enantiomeric Excess2010Ingår i: ChemCatChem, ISSN 1867-3880, E-ISSN 1867-3899, Vol. 2, nr 6, s. 683-693Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Kinetic modeling of a recycling procedure in which the minor product enantiomer from an enantioselective catalytic reaction is selectively retransformed to starting material by a second chiral catalyst demonstrates that the enantiomeric excess of the product is not affected by the relative amounts of the two catalysts, but that the yield increases when the amount of the catalyst for the product-forming reaction is increased. The yield, but not the enantiomeric excess, is also affected by the initial substrate concentration. The recycling process is compared to sequential processes in which either the second catalyst is added after completion of the first reaction or in which the two catalysts are added simultaneously. In the sequential processes, high enantioselectivity can be obtained at the expense of product yield, whereas under recycling conditions both high enantiomeric excess and high yield can be achieved. Experimental data from a recycling procedure providing qualitative support for results from kinetic modeling are presented.

  • 6.
    Fransson, Linda
    et al.
    KTH, Skolan för bioteknologi (BIO), Centra, Albanova VinnExcellence Center for Protein Technology, ProNova.
    Moberg, Christina
    KTH, Skolan för kemivetenskap (CHE), Kemi, Organisk kemi.
    Gaining Selectivity by Combining Catalysts: Sequential versus Recycling Processes2010Ingår i: CHEMCATCHEM, ISSN 1867-3880, Vol. 2, nr 12, s. 1523-1532Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    Highly enantioenriched chiral products may be obtained by using a combination of two moderately selective catalysts. Sequential enantioselective transformations comprising an asymmetric reaction followed by a kinetic resolution of the scalemic product mixture obtained in the first step are well known. In such processes, the minor, undesired enantiomer is transformed to a compound that can be more easily separated from the major enantiomer. Although chiral compounds may be obtained with high enantiopurity by such coupled processes, the yield of the desired product necessarily suffers. Recycling processes, whereby the minor enantiomer is transformed to prochiral starting material, avoid this limitation. In this Mini-review, different types of sequential catalytic processes using two reinforcing catalysts are surveyed and their advantages and limitations discussed in relation to recycling processes.

  • 7.
    Graber, Marianne
    et al.
    Univ La Rochelle, Lab Biotechnol & Chim Bioorgan.
    Irague, Romain
    Univ La Rochelle, Lab Biotechnol & Chim Bioorgan.
    Rosenfeld, Eric
    Univ La Rochelle, Lab Biotechnol & Chim Bioorgan.
    Lamare, Sylvain
    Univ La Rochelle, Lab Biotechnol & Chim Bioorgan.
    Fransson, Linda
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Hult, Karl
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Solvent as a competitive inhibitor for Candida antarctica lipase B2007Ingår i: Biochimica et Biophysica Acta - Proteins and Proteomics, ISSN 1570-9639, E-ISSN 1878-1454, Vol. 1774, nr 8, s. 1052-1057Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In enzyme-catalyzed reactions, the choice of solvent often has a marked effect on the reaction outcome. In this paper, it is shown that solvent effects could be explained by the ability of the solvent to act as a competitive inhibitor to the substrate. Experimentally, the effect of six solvents, 2-pentanone, 3-pentanone, 2-methyl-2-pentanol, 3-methyl-3-pentanot, 2-methylpentane and 3-methylpentane, was studied in a solid/gas reactor. As a model reaction, the CALB-catalyzed transacylation between methyl propanoate and I -propanol, was studied. It was shown that both ketones inhibited the enzyme activity whereas the tertiary alcohols and the hydrocarbons did not. Alcohol inhibition constants, K-il were changed to "K-i", determined in presence of 2-pentanone, 3-pentanone, and 3-methyl-3-pentanol, confirmed the marked inhibitory character of the ketones and an absence of inhibition of 3-methyl-3-pentanol. The molecular modeling study was performed on three solvents, 2-pentanone, 2-methyl-2-pentanol and 2-methyl pentane. It showed a clear inhibitory effect for the ketone and the tertiary alcohol, but no effect for the hydrocarbon. No change in enzyme conformation was seen during the simulations. The study led to the conclusion that the effect of added organic component on lipase catalyzed transacylation could be explained by the competitive inhibitory character of solvents towards the first binding substrate methyl propanoate.

  • 8.
    Hedin, Eva . M. K.
    et al.
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Hoyrup, P.
    Patkar, S. A.
    Vind, J.
    Svendsen, A.
    Fransson, L.inda
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Hult, Karl
    KTH, Tidigare Institutioner                               , Biokemi och biokemisk teknologi.
    Interfacial orientation of Thermomyces lanuginosa lipase on phospholipid vesicles investigated by electron spin resonance relaxation spectroscopy2002Ingår i: Biochemistry, ISSN 0006-2960, E-ISSN 1520-4995, Vol. 41, nr 48, s. 14185-14196Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The binding orientation of the interfacially activated Thermomyces lanuginosa lipase (TLL, EC 3.1.1.3) on phospholipid vesicles was investigated using site-directed spin labeling and electron spin resonance (ESR) relaxation spectroscopy. Eleven TLL single-cysteine mutants, each with the mutation positioned at the surface of the enzyme, were selectively spin labeled with the nitroxide reagent (1-oxyl-2,2,5,5-tetramethyl-Delta(3)-pyrroline-3-methyl) methanethiosulfonate. These were studied together with small unilamellar vesicles (SUV) consisting of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglycerol (POPG), to which TLL has previously been shown to bind in a catalytically active form [Cajal, Y., et al. (2000) Biochemistry, 39, 413-423]. The orientation of TLL with respect to the lipid membrane was investigated using, a water-soluble spin relaxation agent. chromium(III) oxalate (Crox), and a recently developed ESR relaxation technique [Lin, Y., et al. (1998) Science 279, 1925-1929], here modified to low microwave amplitude (< 0.36 G). The exposure to Crox for the spin label at the different positions on the surface of TLL was determined in the absence and presence of vesicles. The spin label at positions Gly61-Cys and Thr267-Cys, closest to the active site nucleophile Ser146 of the positions analyzed, displayed the lowest exposure factors to the membrane-impermeable spin relaxant, indicating the proximity to the vesicle surface. As an independent technique, fluorescence spectroscopy was employed to measure fluorescence quenching of dansyl-labeled POPG vesicles as exerted by the protein-bound spin labels. The resulting Stern-Volmer quenching constants showed excellent agreement with the ESR exposure factors. An interfacial orientation of TLL is proposed on the basis of the obtained results.

  • 9. Heinze, Birgit
    et al.
    Kourist, Robert
    Fransson, Linda
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Hult, Karl
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Bornscheuer, Uwe T.
    Highly enantioselective kinetic resolution of two tertiary alcohols using mutants of an esterase from Bacillus subtilis2007Ingår i: Protein Engineering Design & Selection, ISSN 1741-0126, E-ISSN 1741-0134, Vol. 20, nr 3, s. 125-131Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Enzyme-catalyzed kinetic resolutions of secondary alcohols are a standard procedure today and several lipases and esterases have been described to show high activity and enantioselectivity. In contrast, tertiary alcohols and their esters are accepted only by a few biocatalysts. Only lipases and esterases with a conserved GGG(A)X-motif are active, but show low activity combined with low enantioselectivity in the hydrolysis of tertiary alcohol esters. We show in this work that the problematic autohydrolysis of certain compounds can be overcome by medium and substrate engineering. Thus, 3-phenylbut-1-yn-3-yl acetate was hydrolyzed by the esterase from Bacillus subtilis (BS2, mutant Gly105Ala) with an enantioselectivity of E = 56 in the presence of 20% (v/v) DMSO compared to E = 28 without a cosolvent. Molecular modeling was used to study the interactions between BS2 and tertiary alcohol esters in their transition state in the active site of the enzyme. Guided by molecular modeling, enzyme variants with highly increased enantioselectivity were created. For example, a Glu188Asp mutant converted the trifluoromethyl analog of 3-phenylbut-1-yn-3-yl acetate with an excellent enantioselectivity (E > 100) yielding the (S)-alcohol with > 99%ee. In summary, protein engineering combined with medium and substrate engineering afforded tertiary alcohols of very high enantiomeric purity.

  • 10.
    Kourist, Robert
    et al.
    Univ Greifswald, Dept Biotechnol & Enzyme Catalysis.
    Bartsch, Sebastian
    Univ Greifswald, Dept Biotechnol & Enzyme Catalysis.
    Fransson, Linda
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Hult, Karl
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Bornscheuer, Uwe T.
    Univ Greifswald, Dept Biotechnol & Enzyme Catalysis.
    Understanding promiscuous amidase activity of an esterase from Bacillus subtilis2008Ingår i: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 9, nr 1, s. 67-69Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Water works. Bacillus subtilis esterase BS2 is a promiscuous esterase that shows amidase activity. This amidase activity was shown to depend on a hydrogen-bond network with the substrate amide hydrogen (indicated by arrow). When this stabilising hydrogen bond network was removed by a point mutation, the amide activity was significantly lowered in comparison with the esterase activity. (Figure Presented)

  • 11.
    Léonard, Valérie
    et al.
    Univ Rochelle, FRE CNRS 2766, Lab Biotechnol & Chim Bioorgan.
    Fransson, Linda
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Lamare, Sylvain
    Univ Rochelle, FRE CNRS 2766, Lab Biotechnol & Chim Bioorgan.
    Hult, Karl
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Graber, Marianne
    Univ Rochelle, FRE CNRS 2766, Lab Biotechnol & Chim Bioorgan.
    A water molecule in the stereospecificity pocket of Candida antarctica lipase B enhances enantioselectivity towards pentan-2-ol2007Ingår i: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 8, nr 6, s. 662-667Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of water activity on enzyme-catalyzed enantioselective transesterification was studied by using a solid/gas reactor. The experimental results were compared with predictions from molecular modelling. The system studied was the esterification of pentan-2-ol with methylpropanoate as acyl donor and lipase B from Candida antarctica as catalyst. The data showed a pronounced water-activity effect on both reaction rote and enantioselectivity. The enantioselectivity increased from 100, at water activity close to zero, to a maximum of 320, at a water activity of 0.2. Molecular modelling revealed how a water molecule could bind in the active site and obstruct the binding of the slowly reacting enantiomer. Measurements of enantioselectivity at different water-activity values and temperatures showed that the water molecule had a high affinity for the stereospecificity pocket of the active site with a binding energy of 9 kJ mol(-1), and that it lost all its degrees of rotation, corresponding to an entropic energy of 37 Jmol(-1)K(-1).

  • 12.
    Ottosson, Jenny
    et al.
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Fransson, Linda
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Hult, Karl
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Substrate entropy in enzyme enantioselectivity: An experimental and molecular modeling study of a lipase2002Ingår i: Protein Science, ISSN 0961-8368, E-ISSN 1469-896X, Vol. 11, nr 6, s. 1462-1471Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The temperature dependence of the enantioselectivity of Candida antarctica lipase B for 3-hexanol, 2-butanol, 3-methyl-2-butanol, 3,3-dimethyl-2-butanol, and 1-bromo-2-butanol revealed that the differential activation entropy, Delta(R-S)Delta(S)(divided bydivided by)., was as significant as the differential activation enthalpy, Delta(R-S)DeltaH(divided bydivided by), to the enantiomeric ratio, E. 1-Bromo-2-butanol, with isosteric substituents, displayed the largest Delta(R-S)DeltaS(divided bydivided by) 3-Hexanol displayed, contrary to other sec-alcohols, a positive Delta(R-S)DeltaS(divided bydivided by). In other words, for 3-hexanol the preferred R-enantiomer is not only favored by enthalpy but also by entropy. Molecular dynamics (MID) simulations and systematic search calculations of the substrate accessible volume within the active site revealed that the (R)-3-hexanol transition state (TS) accessed a larger volume within the active site than the (S)-3-hexanol TS. This correlates well with the hi-her TS entropy of (R)-3-hexanol. In addition, this enantiomer did also yield a higher number of allowed conformations, N, from the systematic search routines, than did the S-enantiomer. The substrate accessible volume was greater for the enantiomer preferred by entropy also for 2-butanol. For 3,3-dimethyl-2-butanol, however, neither MD-simulations nor systematic search calculations yielded substrate accessible volumes that correlate to TS entropy. Ambiguous results were achieved for 3-methyl-2-butanol.

  • 13.
    Ottosson, Jenny
    et al.
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Fransson, Linda
    KTH, Tidigare Institutioner                               , Bioteknologi.
    King, Jerry W.
    National Center for Agricultural Utilization Research, ARS/USDA.
    Hult, Karl
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Size as a parameter for solvent effects on Candida antarctica lipase B enantioselectivity2002Ingår i: Biochimica et Biophysica Acta - Protein Structure and Molecular Enzymology, ISSN 0167-4838, E-ISSN 1879-2588, Vol. 1594, nr 2, s. 325-334Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Changes in solvent type were shown to yield significant improvement of enzyme enantioselectivity. The resolution of 3-methyl-2-butanol catalyzed by Candida antarctica lipase B, CALB, was studied in eight liquid organic solvents and supercritical carbon dioxide, SCCO2. Studies of the temperature dependence of the enantiomeric ratio allowed determination of the enthalpic (Delta(R-S)Delta H-double dagger) as well as the entropic (Delta(R-S)Delta S-double dagger) contribution to the overall enantioselectivity (Delta(R-S)Delta G(double dagger) = -RTlnE). A correlation of the enantiomeric ratio, E. to the van der Waals volume of the solvent molecules was observed and suggested as one of the parameters that govern solvent effects on enzyme catalysis. An enthalpy-entropy compensation relationship was indicated between the studied liquid solvents. The enzymatic mechanism must be of a somewhat different nature in SCCO2, as this reaction in this medium did not follow the enthalpy-entropy compensation relation.

  • 14.
    Raza, Sami
    et al.
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Fransson, Linda
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Hult, Karl
    KTH, Tidigare Institutioner                               , Bioteknologi.
    Enantioselectivity in Candida antarctica lipase B: A molecular dynamics study2001Ingår i: Protein Science, ISSN 0961-8368, E-ISSN 1469-896X, Vol. 10, nr 2, s. 329-338Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A major problem in predicting the enantioselectivity of an enzyme toward substrate molecules is that even high selectivity toward one substrate enantiomer over the other corresponds to a very small difference in free energy. However, total free energies in enzyme-substrate systems are very large and fluctuate significantly because of general protein motion. Candida antarctica lipase B (CALB), a serine hydrolase, displays enantioselectivity toward secondary alcohols. Here, we present a modeling study where the aim has been to develop a molecular dynamics-based methodology for the prediction of enantioselectivity in CALB. The substrates modeled (seven in total) were 3-methyl-2-butanol with various aliphatic carboxylic acids and also 2-butanol, as well as 3,3-dimethyl-2-butanol with octanoic acid. The tetrahedral reaction intermediate was used as a model of the transition state. Investigative analyses were performed on ensembles of nonminimized structures and focused on the potential energies of a number of subsets within the modeled systems to determine which specific regions are important for the prediction of enantioselectivity. One category of subset was based on atoms that make up the core structural elements of the transition state. We considered that a more favorable energetic conformation of such a subset should relate to a greater likelihood for catalysis to occur, thus reflecting higher selectivity. The results of this study conveyed that the use of this type of subset was viable for the analysis of structural ensembles and yielded good predictions of enantioselectivity.

  • 15.
    Svedendahl, Maria
    et al.
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Jovanovic, Biljana
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Fransson, Linda
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Berglund, Per
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Suppressed Native Hydrolytic Activity of a Lipase to Reveal Promiscuous Michael Addition Activity in Water2009Ingår i: CHEMCATCHEM, ISSN 1867-3880, Vol. 1, nr 2, s. 252-258Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Suppression of,the,native hydrolytic activity of Pseudozyma antarctica lipase B (PalB) (formerly Candida antarctica lipase B) in water is demonstrated. By replacing the catalytic Ser 105 residue with an alanine unit, promiscuous Michael addition activity is favored. A Michael addition reaction between methyl acrylate and acetylacetone was explored as a model system. For the PalB Ser 105 Ala mutant, the hydrolytic activity was suppressed more than 1000 times and at the same time, the Michael addition activity was increased by a factor of 100. Docking studies and molecular dynamics simulations revealed an increased ability of the PalB Ser 105 Ala mutant to harbor the substrates close to a catalytically competent conformation.

  • 16. Vallikivi, I.
    et al.
    Fransson, Linda
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Hult, Karl
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Järving, I.
    Pehk, T.
    Samel, N.
    Tougu, V.
    Villo, L.
    Parve, O.
    The modelling and kinetic investigation of the lipase-catalysed acetylation of stereoisomeric prostaglandins2005Ingår i: Journal of Molecular Catalysis B: Enzymatic, ISSN 1381-1177, E-ISSN 1873-3158, Vol. 35, nr 1-3, s. 62-69Artikel i tidskrift (Refereegranskat)
    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.

  • 17. Veld, Martijn A. J.
    et al.
    Fransson, Linda
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Palmans, Ania R. A.
    Meijer, E. W.
    Hult, Karl
    KTH, Skolan för bioteknologi (BIO), Biokemi.
    Lactone Size Dependent Reactivity in Candida Antarctica Lipase B: A Molecular Dynamics and Docking Study2009Ingår i: ChemBioChem (Print), ISSN 1439-4227, E-ISSN 1439-7633, Vol. 10, nr 8, s. 1330-1334Artikel i tidskrift (Refereegranskat)
  • 18.
    Wingstrand, Erica
    et al.
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Fransson, Linda
    KTH, Skolan för bioteknologi (BIO).
    Laurell, Anna
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Hult, Karl
    KTH, Skolan för bioteknologi (BIO).
    Moberg, Christina
    KTH, Skolan för kemivetenskap (CHE), Kemi.
    Minor enantiomer recycling: Metal catalyst, organocatalyst and biocatalyst working in concert2009Ingår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 15, nr 44, s. 12107-12113Artikel i tidskrift (Refereegranskat)
    Abstract [en]

     A minor enantiomer recycling one-pot procedure employing two reinforcing chiral catalysts has been developed. Continuous regeneration of the achiral starting material is effected via selective enzyme-catalyzed hydrolysis of the minor product enantiomer from Lewis acid-Lewis base catalyzed addition of acyl cyanides to prochiral aldehydes in a two-phase solvent system. The process provides O-acylated cyanohydrins in close to perfect enantioselectivities, higher than those obtained in the direct process, and in high yields. A combination of a (SS)salen Ti Lewis acid and Candida antarctica lipase B provides the products with R absolute configuration, whereas the opposite enantiomer is obtained from the (R,R)-salen Ti complex and Candida rugosa lipase.

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