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  • 251.
    Eklund, Robert
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Widmalm, Göran
    Molecular dynamics simulations of an oligosaccharide using a force field modified for carbohydrates2003Inngår i: Carbohydrate Research, ISSN 0008-6215, Vol. 338, nr 5, s. 393-398Artikkel i tidsskrift (Fagfellevurdert)
  • 252.
    Ekström, Jesper
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Abrahamsson, Maria
    Olson, Carol
    Bergquist, Jonas
    Kanyak, Feliz B.
    Eriksson, Lars
    Sun, Licheng
    Åkermark, Björn
    Becker, Hans-Christian
    Hammarström, Leif
    Ott, Sascha
    Bio Inspired Side-on Attachment of a Ruthenium Photo-sensitizer to an Iron Hydrogenase Active Site Model2006Inngår i: Dalton Transactions, ISSN 1477-9226, nr 38, s. 4599-4606Artikkel i tidsskrift (Fagfellevurdert)
  • 253.
    Ekström, Jesper
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Wettergren, Jenny
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Adolfsson, Hans
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    A Simple and Efficient Catalytic Method for the Reduction of Ketones2007Inngår i: Advanced Synthesis and Catalysis, ISSN 1615-4150, E-ISSN 1615-4169, Vol. 349, nr 10, s. 1609-1613Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A range of ketones was efficiently reduced in the presence of catalytic amounts of lithium isopropoxide in 2-propanol under microwave heating, with alcohol products being formed in yields up to 99 %.

  • 254.
    Endo, Yoshinori
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Aerobic Lactonization of Diols by Biomimetic Oxidation2011Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 17, nr 45, s. 12596-12601Artikkel i tidsskrift (Fagfellevurdert)
  • 255.
    Endo, Yoshinori
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Biomimetic Oxidative Coupling of Benzylamines and 2-Aminophenols: Synthesis of Benzoxazoles2012Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 18, nr 43, s. 13609-13613Artikkel i tidsskrift (Fagfellevurdert)
  • 256.
    Engelmark Cassimjee, Karim
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Kadow, Maria
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Wikmark, Ylva
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Svedendahl Humble, Maria
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Rothstein, M. L.
    Rothstein, D. M.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    A general protein purification and immobilization method on controlled porosity glass: biocatalytic applications2014Inngår i: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 50, nr 65, s. 9134-9137Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A general combined purification and immobilization method to facilitate biocatalytic process development is presented. The support material, EziG (TM), is based on controlled porosity glass (CPG) or polymer-coated versions thereof (HybCPG) and binds protein affinity tags. Biocatalytic reactions in aqueous and organic media with seven enzymes of biocatalytic interest are shown.

  • 257.
    Engelmark Cassimjee, Karim
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Manta, Bianca
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    A quantum chemical study of the ω-transaminase reaction mechanism2015Inngår i: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 13, nr 31, s. 8453-8464Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    ω-Transaminases are valuable tools in biocatalysis due to their stereospecificity and their broad substrate range. In the present study, the reaction mechanism of Chromobacterium violaceum ω-transaminase is investigated by means of density functional theory calculations. A large active site model is designed based on the recent X-ray crystal structure. The detailed energy profile for the half-transamination of (S)-1-phenylethylamine to acetophenone is calculated and the involved transition states and intermediates are characterized. The model suggests that the amino substrate forms an external aldimine with the coenzyme pyridoxal-5′-phosphate (PLP), through geminal diamine intermediates. The external aldimine is then deprotonated in the rate-determining step, forming a planar quinonoid intermediate. A ketimine is then formed, after which a hemiaminal is produced by the addition of water. Subsequently, the ketone product is obtained together with pyridoxamine-5′-phosphate (PMP). In the studied half-transamination reaction the ketone product is kinetically favored. The mechanism presented here will be valuable to enhance rational and semi-rational design of engineered enzyme variants in the development of ω-transaminase chemistry.

  • 258.
    Engqvist, Magnus
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Casas, J
    Sundén, H
    Ibrahem, I
    Córdova, A
    Direct Organoctalytic Asymmetric α-Oxidation of Ketones with Iodosobenzene and N-sulfonyloxaziridine2004Inngår i: Tetrahedron letters, ISSN 0040-4039, Vol. 46, nr 12, s. 2053-2057Artikkel i tidsskrift (Fagfellevurdert)
  • 259.
    Engström, Karin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Johnston, Eric V.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Verho, Oscar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Gustafson, Karl P. J.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Shakeri, Mozaffar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Tai, Cheuk-Wai
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Co-immobilization of an Enzyme and a Metal into the Compartments of Mesoporous Silica for Cooperative Tandem Catalysis: An Artificial Metalloenzyme2013Inngår i: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 52, nr 52, s. 14006-14010Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Surpassing nature: A hybrid catalyst in which Candida antarctica lipase B and a nanopalladium species are co-immobilized into the compartments of mesoporous silica is presented. The metal nanoparticles and the enzyme are in close proximity to one another in the cavities of the support. The catalyst mimics a metalloenzyme and was used for dynamic kinetic resolution of a primary amine in high yield and excellent enantioselectivity.

  • 260.
    Engström, Karin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Nyhlén, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sandström, Anders G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Directed evolution of an enantioselective lipase with broad substrate scope for hydrolysis of α-substituted esters2010Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, nr 20, s. 7038-7042Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A variant of Candida antarctica lipase A (CalA) was developed for the hydrolysis of α-substituted p-nitrophenyl esters by directed evolution. The E values of this variant for 7 different esters was 45−276, which is a large improvement compared to 2−20 for the wild type. The broad substrate scope of this enzyme variant is of synthetic use, and hydrolysis of the tested substrates proceeded with an enantiomeric excess between 95−99%. A 30-fold increase in activity was also observed for most substrates. The developed enzyme variant shows (R)-selectivity, which is reversed compared to the wild type that is (S)-selective for most substrates.

  • 261.
    Engström, Karin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Nyhlén, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sandström, Anders G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Enantioselective Kinetic Resolution of p-Nitrophenyl 2-Phenylpropanoate by a Variant of Candida antarctica Lipase A Developed by Directed Evolution2010Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, nr 20, s. 7038-7042Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A variant of Candida antarctica lipase A (CalA) was developed for the hydrolysis of α-substituted p-nitrophenyl esters by directed evolution. The E values of this variant for 7 different esters was 45−276, which is a large improvement compared to 2−20 for the wild type. The broad substrate scope of this enzyme variant is of synthetic use, and hydrolysis of the tested substrates proceeded with an enantiomeric excess between 95−99%. A 30-fold increase in activity was also observed for most substrates. The developed enzyme variant shows (R)-selectivity, which is reversed compared to the wild type that is (S)-selective for most substrates.

  • 262.
    Engström, Karin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Shakeri, Mozaffar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Dynamic Kinetic Resolution of β-Amino Esters by a Heterogeneous System of a Palladium Nanocatalyst and Candida antarctica Lipase A2011Inngår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 10, s. 1827-1830Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A dynamic kinetic resolution (DKR) of β-amino esters have been developed by the use of a heterogeneous racemization catalyst and an immobilized enzyme that accepts aromatic, heteroaromatic and aliphatic substrates. The reaction conditions were optimized to yield an efficient catalytic system without by-product formation. The products are obtained in 96–99 % ee and high yields

  • 263.
    Engström, Karin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Vallin, Michaela
    Hult, Karl
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Kinetic resolution of diarylmethanols using a mutated variant of lipase CALB2012Inngår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 68, nr 37, s. 7613-7618Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An enzymatic kinetic resolution of diarylmethanols via acylation has been developed. This was achieved by the use of a mutated variant of CALB that accepts larger substrates compared to the wild type. By the use of diarylmethanols with two differently sized aryl groups, enantioselective transformations were achieved. A larger size-difference led to a higher enantioselectivity. In addition, substrates with electronically different aryl groups, such as phenyl and pyridyl, also gave an enantioselective reaction. The highest E value was observed with a substrate where steric and electronic effects were combined.

  • 264.
    Engström, Karin
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Vallin, Michaela
    Syrén, Per-Olof
    Hult, Karl
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mutated variant of Candida antarctica lipase B in (S)-selective dynamickinetic resolution of secondary alcohols2011Inngår i: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 9, nr 1, s. 81-82Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An (S)-selective dynamic kinetic resolution of secondaryalcohols, employing a mutated variant of Candida antarcticalipase B (CalB) gave products in 84–88% yield and in 90–97%ee.

  • 265.
    Engström, Olof
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mobarak, Hani
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Ståhle, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Conformational Dynamics and Exchange Kinetics of N-Formyl and N-Acetyl Groups Substituting 3-Amino-3,6-dideoxy-alpha-D-galactopyranose, a Sugar Found in Bacterial O-Antigen Polysaccharides2017Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 121, nr 41, s. 9487-9497Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Three dimensional shape and conformation of. carbohydrates are important factors in molecular recognition events and the N-acetyl group of a monosaccharide residue can function as a conformational gatekeeper whereby it influences the overall shape of the oligosaccharide. NMR spectroscopy and quantum mechanics (QM) calculations are used herein to investigate both the conformational preferences and the dynamic behavior of N-acetyl and N-formyl substituents of 3-amino-3,6-dideoxy-alpha-D-galactopyranose, a sugar and substitution pattern found in bacterial O-antigen polysaccharides. QM calculations suggest that the amide oxygen can be involved in hydrogen bonding with the axial OH4 group primarily but also with the equatorial OH2 group. However, an NMR J coupling analysis indicates that the 01 torsion angle, adjacent to the sugar ring, prefers an ap conformation where conformations <180 degrees also are accessible, but does not allow for intramolecular hydrogen bonding. In the formyl-substituted compound (4)J(HH) coupling constants to the exo-cyclic group were detected and analyzed. A van't Hoff analysis revealed that the trans conformation at the amide bond is favored by Delta G degrees approximate to - 0.8 kcal.mol(-1) in the formyl-containing compound and with Delta G degrees approximate to -2.5 kcal.mol(-1) when the N-acetyl group is the substituent. In both cases the enthalpic term dominates to the free energy, irrespective of water or DMSO as solvent, with only a small contribution from the entropic term. The cis-trans isomerization of the theta(2) torsion angle, centered at the amide bond, was also investigated by employing H-1 NMR line shape analysis and C-13 NMR saturation transfer experiments. The extracted transition rate constants were utilized to calculate transition energy barriers that were found to be about 20 kcal.mol(-1) in both DMSO-d(6) and D2O. Enthalpy had a higher contribution to the energy barriers in DMSO-d(6) compared to in D2O, where entropy compensated for the loss of enthalpy.

  • 266.
    Engström, Olof
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Muñoz, Antonio
    Illescas, Beatriz M.
    Martin, Nazario
    Ribeiro-Viana, Renato
    Rojo, Javier
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Investigation of glycofullerene dynamics by NMR spectroscopy2015Inngår i: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 13, nr 32, s. 8750-8755Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Glycofullerenes, in which carbohydrate molecules are attached via a linker to a [60]fullerene core, facilitate spherical presentation of glyco-based epitopes. We herein investigate the dynamics of two glycofullerenes, having 12 and 36 mannose residues at their periphery, by NMR translational diffusion and quantitative C-13 relaxation studies employing a model-free approach for their interpretation. The sugar residues are shown to be highly flexible entities with S-2 < 0.2 in both compounds. Notably, the larger glycofullerene with longer linkers shows faster internal dynamics and higher flexibility than its smaller counterpart. The dynamics and flexibility as well as the slower translational diffusion of the larger glycofullerene, thereby favoring rebinding to a receptor, may together with its spatial extension explain why it is better than the smaller one at blocking the DC-SIGN receptor and inhibiting the infection by pseudotyped Ebola virus particles.

  • 267.
    Erbing, Elis
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sanz-Marco, Amparo
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Vazquez-Romero, Ana
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Malmberg, Jesper
    Johansson, Magnus J.
    Gomez-Bengoa, Enrique
    Martín-Matute, Belén
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Base- and Additive-Free Ir-Catalyzed ortho-Iodination of Benzoic Acids: Scope and Mechanistic Investigations2018Inngår i: ACS Catalysis, ISSN 2155-5435, E-ISSN 2155-5435, Vol. 8, nr 2, s. 920-925Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A protocol for the C-H activation/iodination of benzoic acids catalyzed by a simple iridium complex has been developed. The method described in this paper allows the ortho-selective iodination of a variety of benzoic acids under extraordinarily mild conditions in the absence of any additive or base in 1,1,1,3,3,3-hexafluoroisopropanol as the solvent. The iridium catalyst used tolerates air and moisture, and selectively gives ortho-iodobenzoic acids with high conversions. Mechanistic investigations revealed that an Ir(III)/Ir(V) catalytic cycle operates, and that the unique properties of HFIP enables the C-H iodination using the carboxylic moiety as a directing group.

  • 268.
    Erbing, Elis
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Vazquez-Romero, Ana
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bermejo Gómez, Antonio
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Platero-Prats, Ana E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Carson, Fabian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Zou, Xiaodong
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Tolstoy, Päivi
    Martín-Matute, Belén
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    General, Simple, and Chemoselective Catalysts for the Isomerization of Allylic Alcohols: The Importance of the Halide Ligand2016Inngår i: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 22, nr 44, s. 15659-15663Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Remarkably simple Ir-III catalysts enable the isomerization of primary and sec-allylic alcohols under very mild reaction conditions. X-ray absorption spectroscopy (XAS) and mass spectrometry (MS) studies indicate that the catalysts, with the general formula [Cp*Ir-III], require a halide ligand for catalytic activity, but no additives or additional ligands are needed.

  • 269.
    Ericsson, Daniel J.
    et al.
    1Department of Cell and Molecular Biology, Uppsala University, Biomedical Center.
    Kasrayan, Alex
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Johansson, Patrik
    1Department of Cell and Molecular Biology, Uppsala University, Biomedical Center.
    Bergfors, Terese
    1Department of Cell and Molecular Biology, Uppsala University, Biomedical Center.
    Sandström, Anders G.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Mowbray, Sherry L.
    Department of Molecular Biology, Swedish University of Agricultural Sciences, Biomedical Center.
    X-Ray structure of Candida antarctica lipase A shows a novel lid structure and a likely mode of interfacial activation2008Inngår i: Journal of Molecular Biology, ISSN 0022-2836, Vol. 376, nr 1, s. 109-119Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In nature, lipases (EC 3.1.1.3) catalyze the hydrolysis of triglycerides to form glycerol and fatty acids. Under the appropriate conditions, the reaction is reversible, and so biotechnological applications commonly make use of their capacity for esterification as well as for hydrolysis of a wide variety of compounds. In the present paper, we report the X-ray structure of lipase A from Candida antarctica, solved by single isomorphous replacement with anomalous scattering, and refined to 2.2-Å resolution. The structure is the first from a novel family of lipases. Contrary to previous predictions, the fold includes a well-defined lid as well as a classic α/β hydrolase domain. The catalytic triad is identified as Ser184, Asp334 and His366, which follow the sequential order considered to be characteristic of lipases; the serine lies within a typical nucleophilic elbow. Computer docking studies, as well as comparisons to related structures, place the carboxylate group of a fatty acid product near the serine nucleophile, with the long lipid tail closely following the path through the lid that is marked by a fortuitously bound molecule of polyethylene glycol. For an ester substrate to bind in an equivalent fashion, loop movements near Phe431 will be required, suggesting the primary focus of the conformational changes required for interfacial activation. Such movements will provide virtually unlimited access to solvent for the alcohol moiety of an ester substrate. The structure thus provides a basis for understanding the enzyme's preference for acyl moieties with long, straight tails, and for its highly promiscuous acceptance of widely different alcohol and amine moieties. An unconventional oxyanion hole is observed in the present structure, although the situation may change during interfacial activation

  • 270.
    Eriksson, Kristofer
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Gothelid, Emmanuelle
    Puglia, Carla
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Oscarsson, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Performance of a biomimetic oxidation catalyst immobilized on silica particles2013Inngår i: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 303, s. 16-21Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A biomimetic oxidation catalyst, cobalt porphyrin with thiol linkers, was chemically conjugated to silica particles and utilized in the oxidation of hydroquinone to benzoquinone. The cobalt porphyrin/silica particle catalyst was characterized with Inductively Coupled Plasma (ICP) and X-ray Photoelectron Spectroscopy (XPS). The catalytic performance of the cobalt porphyrin molecules was compared to previous results for the same catalyst grafted to a gold surface and on silicon wafers. The measured catalytic activity, after background correction, was 100 times higher than that of its homogeneous counterpart, 10 times higher than that on a silicon wafer, and almost the same as that on a gold surface. The turnover frequency rates after 400 h are still comparable with initial rates reported for homogeneous porphyrins and salophens, whereas the use of particles as support increases the active surface area, which removes the limitations for scale-up associated with the previously used silicon wafers and gold surfaces.

  • 271.
    Eriksson, Kristofer
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Johansson, Lars Erik
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Göthelid, Emmanuelle
    Nyholm, Leif
    Oscarsson, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Manufacturing of Anisotropic Particles by Site Specific Oxidation of Thiols2012Inngår i: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 22, nr 16, s. 7681-7683Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel method for the manufacturing of functional anisotropic particles based on an inexpensive and straightforward electrochemical approach is presented. The method enables large-scale manufacturing of anisotropic particles as well as fabrication of multifunctional beads which may be used in the design of barcodes for multiplex diagnostics.

  • 272. Eriksson, Kristofer L. E.
    et al.
    Chow, Winnie W. Y.
    Puglia, Carla
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Göthelid, Emmanuelle
    Oscarsson, Sven
    Performance of a biomimetic oxidation catalyst immobilized on silicon wafers: comparison with its gold congener2010Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 26, nr 21, s. 16349-16354Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    With the aim of extending the usefulness of an existing biomimetic catalytic system, cobalt porphyrin catalytic units with thiol linkers were heterogenized via chemical grafting to silicon wafers and utilized for the catalytic oxidation of hydroquinone to p-benzoquinone. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology and composition of the heterogeneous catalyst. The results of the catalytic oxidation of hydroquinone obtained with porphyrins grafted on silicon were compared with those obtained earlier with the same catalyst in homogeneous phase and immobilized on gold. It was found that the catalysis could run over 400 h, without showing any sign of deactivation. The measured catalytic activity is at least 10 times higher than that measured under homogeneous conditions, but also 10 times lower than that observed with the catalytic unit immobilized on gold. The reasons of this discrepancy are discussed in term of substrate influence and overlayer organization. The silicon-immobilized catalyst has potential as an advanced functional material with applications in oxidative heterogeneous catalysis of organic reactions, as it combines long-term relatively high activity with low cost.

  • 273.
    Eriksson, Kristofer
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Palmgren, Pal
    Nyholm, Leif
    Oscarsson, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Electrochemical Synthesis of Gold and Protein Gradients on Particle Surfaces2012Inngår i: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 28, nr 28, s. 10318-10323Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A straightforward, versatile approach to the production of protein gradients on planar and spherical particle surfaces is described. The method is based on the spatially controlled oxidation of thiolated surfaces by Au(III) ions generated via the electrochemical oxidation of a gold electrode in a phosphate-buffered saline solution (10 mM PBS, pH 7.2, 150 mM NaCl). Because the gold electrode is in direct contact with the thiolated surfaces, the released Au(III) ions, which are present as Au(III) chloride complexes, give rise to the formation of a surface gradient of Au(I)-thiolate complexes depending on the local redox potential given by the local Au(III) concentration. As is shown on the basis of the use of X-ray photoelectron spectroscopy and fluorescently labeled proteins, the Au(I)-thiolate complexes can subsequently be functionalized with thiolated proteins, yielding surface density protein gradients on micrometer-sized nonconducting polymer beads as well as linear Au(I)-thiolate gradients on planar silicon surfaces.

  • 274.
    Eriksson, Kristofer
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Verho, Oscar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Nyholm, Leif
    Oscarsson, Sven
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Dispersed Gold Nanoparticles Supported in the Pores of Siliceous Mesocellular Foam: A Catalyst for Cycloisomerization of Alkynoic Acids to gamma-Alkylidene Lactones2015Inngår i: European Journal of Organic Chemistry, ISSN 1434-193X, E-ISSN 1099-0690, nr 10, s. 2250-2255Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A versatile approach for the production of dispersed thiol-stabilized gold nanoparticles in the pores of siliceous mesocellular foam (MCF) is described. The reported method is based on an electrochemical oxidation of a gold surface generating oxidative Au-III species, which give rise to a surface-confined redox reaction yielding MCF-supported Au-I thiolates. By reducing the corresponding Au-I-S-MCF species with sodium borohydride, thiol-stabilized gold nanoparticles in the size range of 1-8 nm were obtained as determined by transmission electron microscopy. Elemental analysis indicated an Au loading of 3% (w/w) on the MCF. The surface-confined Au nanoparticles were used to catalyze the cycloisomerization of alkynoic acids to the corresponding -alkylidene lactones in high efficiency and complete 5-exo-dig selectivity under mild reaction conditions.

  • 275.
    Eriksson, Lars
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Crystal structure of methyl alpha-L-rhamnopyranosyl-(1 -> 2)-alpha-L-rhamnopyranoside monohydrate2019Inngår i: Acta Crystallographica Section E: Crystallographic Communications, ISSN 2056-9890, Vol. 75, s. 854-857Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The title compound, C13H24O9 center dot H2O, a structural model for part of bacterial O-antigen polysaccharides from Shigella flexneri and Escherichia coli, crystallizes with four independent disaccharide molecules and four water molecules in the asymmetric unit. The conformation at the glycosidic linkage joining the two rhamnosyl residues is described by the torsion angles phi(H) of 39, 30, 37 and 37 degrees, and psi(H) of -32, -35, -31 and -32 degrees, which are the major conformation region known to be populated in an aqueous solution. The hexopyranose rings have the C-1(4) chair conformation. In the crystal, the disaccharide and water molecules are associated through O-H center dot center dot center dot O hydrogen bonds, forming a layer parallel to the bc plane. The layers stack along the a axis via hydrophobic interactions between the methyl groups.

  • 276.
    Eriksson, Lars
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi.
    Widmalm, Göran
    Institutionen för organisk kemi.
    Methyl 3-O-alpha-D-mannopyranosyl beta-D-glucopyranoside tetrahydrate2008Inngår i: Acta Crystallographica Section E, ISSN 1600-5368, Vol. E64, nr 8, s. o1639-o1640Artikkel i tidsskrift (Fagfellevurdert)
  • 277.
    Eriksson, Lars
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Methyl 3-O-alpha-L-fucopyranosyl alpha-D-galactopyranoside: a synchrotron study2012Inngår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 68, s. o528-U1770Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The title compound, C13H24O10 is the methyl glycoside of a structural element alpha-L-Fucp-(1 -> 3)-alpha-D-Galp making up two thirds of the repeating unit in the capsular polysaccharide of Klebsiella K63. The conformation of the title compound is described by the glycosidic torsion angles phi(H) = 55 (1)degrees and psi H = -24 (1)degrees. The hydroxymethyl group in the galactose residue is present in the gauche-trans conformation. In the crystal, O-H center dot center dot center dot O hydrogen bonds connect the disaccharide units into chains along the a-axis direction and further hydrogen bonds cross-link the chains.

  • 278.
    Eriksson, Lars
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för material- och miljökemi (MMK).
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Methyl 3-O-α-l-fucopyranosyl β-d-glucopyranoside tetrahydrate2012Inngår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 68, s. o3180-o3181Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The title compound, C13H24O10·4H2O, is the methyl glycoside of a disaccharide structural element present in the backbone of the capsular polysaccharide from Klebsiella K1, which contains only three sugars and a substituent in the polysaccharide repeating unit. The conformation of the title disaccharide is described by the glycosidic torsion angles ϕH = 51.1 (1)° and ψH = 25.8 (1)°. In the crystal, a number of O—HO hydrogen bonds link the methyl glycoside and water mol­ecules, forming a three-dimensional network. One water mol­ecule is disordered over two positions with occupancies of 0.748 (4) and 0.252 (4).

  • 279. Eriksson, Lars
    et al.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Methyl α-l-rhamnosyl-(1→2)[α-l-rhamnosyl-(1→3)]-α-l-rhamnoside penta­hydrate: synchrotron study2012Inngår i: Acta Crystallographica Section E: Structure Reports Online, ISSN 1600-5368, E-ISSN 1600-5368, Vol. 68, nr 7, s. o2221-o2222Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The title hydrate, C19H34O13·5H2O, contains a vicinally disubstituted tris­accharide in which the two terminal rhamnosyl sugar groups are positioned adjacent to each other. The conformation of the tris­accharide is described by the glycosidic torsion angles ϕ2 = 48 (1)°, ψ2 = −29 (1)°, ϕ3 = 44 (1)° and ψ3 = 4 (1)°, whereas the ψ2 torsion angle represents a conformation from the major state in solution, the ψ3 torsion angle conformation may have been caught near a potential energy saddle-point when compared to its solution structure, in which at least two but probably three conformational states are populated. Extensive inter­molecular O—HO hydrogen bonding is present in the crystal and a water-containing channel is formed along the b-axis direction.

  • 280. Ertem, Mehmed Z.
    et al.
    Cramer, Christopher J.
    Himo, Fahmi
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Siegbahn, Per E. M.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    N-O bond cleavage mechanism(s) in nitrous oxide reductase2012Inngår i: Journal of Biological Inorganic Chemistry, ISSN 0949-8257, E-ISSN 1432-1327, Vol. 17, nr 5, s. 687-698Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Quantum chemical calculations of active-site models of nitrous oxide reductase (N2OR) have been undertaken to elucidate the mechanism of N-O bond cleavage mediated by the supported tetranuclear Cu4S core (Cu-Z) found in the enzymatic active site. Using either a minimal model previously employed by Gorelsky et al. (J. Am. Chem. Soc. 128:278-290, 2006) or a more extended model including key residue side chains in the active-site second shell, we found two distinct mechanisms. In the first model, N2O binds to the fully reduced Cu-Z in a bent mu-(1,3)-O,N bridging fashion between the Cu-I and Cu-IV centers and subsequently extrudes N-2 while generating the corresponding bridged mu-oxo species. In the second model, substrate N2O binds loosely to one of the coppers of Cu-Z in a terminal fashion, i.e., using only the oxygen atom; loss of N-2 generates the same mu-oxo copper core. The free energies of activation predicted for these two alternative pathways are sufficiently close to one another that theory does not provide decisive support for one over the other, posing an interesting problem with respect to experiments that might be designed to distinguish between the two. Effects of nearby residues and active-site water molecules are also explored.

  • 281.
    Fawzy Abdel-Magied, Ahmed
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi. Nuclear Materials Authority, Egypt.
    Solid phase extraction of uranium from phosphoric acid: kinetic and thermodynamic study2017Inngår i: Radiochimica Acta, ISSN 0033-8230, E-ISSN 2193-3405, Vol. 105, nr 10, s. 813-820Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    There is a high interest to develop suitable solid phase extractants for uranium separation from aqueous solutions in order to reduce cost and enhance the efficiency. This paper describes solid phase extraction of uranium(VI) from aqueous phosphoric acid solution using MCM-41 based D2HEPA-TOPO organophosphorous extractants. The mixture of D2HEPA (di-2-ethyl-hexylphosphoric acid) and TOPO (tri-n-octylphosphine oxide) was impregnated into the pores of MCM-41 and the synthesized sorbent was fully characterized. The influences of different factors such as synergistic mixture ratio, phosphoric acid concentration, mixing time and temperature were investigated. The results showed that 90% of uranium(VI) extraction can be achieved within 5 min, using D2HEPATOPO@MCM-41 (mass ratio 2: 1 w/w) from 1 M phosphoric acid containing 64 ppm of uranium at room temperature. High adsorption capacity of uranium(VI) have been achieved at the mentioned conditions. The rate constant for the chemical adsorption of uranium(VI) was 0.988 g mg. 1 min. 1 calculated by the pseudo-second order rate equation. The obtained thermodynamics parameters showed that uranium(VI) adsorption from H-3 PO4 is an exothermic and spontaneous process.

  • 282.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Conde-Alvarez, Raquel
    Ståhle, Jonas
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Holst, Otto
    Iriarte, Maite
    Zhao, Yun
    Arce-Gorvel, Vilma
    Hanniffy, Sean
    Gorvel, Jean-Pierre
    Moriyon, Ignacio
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural Studies of Lipopolysaccharide-defective Mutants from Brucella melitensis Identify a Core Oligosaccharide Critical in Virulence2016Inngår i: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 291, nr 14, s. 7727-7741Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structures of the lipooligosaccharides from Brucella melitensis mutants affected in the WbkD and ManB(core) proteins have been fully characterized using NMR spectroscopy. The results revealed that disruption of wbkD gives rise to a rough lipopolysaccharide (R-LPS) with a complete core structure (beta-D-Glcp-(1 -> 4)-alpha-Kdop-(2 -> 4)[beta-D-GlcpN-(1 -> 6)-beta-D-GlcpN-(1 -> 4)[beta-D-GlcpN-(1 -> 6)]-beta-D-GlcpN-(1 -> 3)-alpha-D-Manp-(1 -> 5)]-alpha-Kdop-(2 -> 6)-beta-D-GlcpN3N4P-(1 -> 6)-alpha-D-GlcpN3N1P), in addition to components lacking one of the terminal beta-D-GlcpN and/or the beta-D-Glcp residues (48 and 17%, respectively). These structures were identical to those of the R-LPS from B. melitensis EP, a strain simultaneously expressing both smooth and R-LPS, also studied herein. In contrast, disruption of man-B-core gives rise to a deep-rough pentasaccharide core (beta-D-Glcp-(1 -> 4)-alpha-Kdop-(2 -> 4)-alpha-Kdop-(2 -> 6)-beta-D-GlcpN3N4P-(1 -> 6)-alpha-D-GlcpN3N1P) as the major component (63%), as well as a minor tetrasaccharide component lacking the terminal beta-D-Glcp residue (37%). These results are in agreement with the predicted functions of the WbkD (glycosyltransferase involved in the biosynthesis of the O-antigen) and ManB(core) proteins (phosphomannomutase involved in the biosynthesis of a mannosyl precursor needed for the biosynthesis of the core and O-antigen). We also report that deletion of B. melitensis wadC removes the core oligosaccharide branch not linked to the O-antigen causing an increase in overall negative charge of the remaining LPS inner section. This is in agreement with the mannosyltransferase role predicted for WadC and the lack of GlcpN residues in the defective core oligosaccharide. Despite carrying the O-antigen essential in B. melitensis virulence, the core deficiency in the wadC mutant structure resulted in a more efficient detection by innate immunity and attenuation, proving the role of the beta-D-GlcpN-(1 -> 6)-beta-D-GlcpN-(1 -> 4)[beta-D-GlcpN-(1 -> 6)]-beta-D-GlcpN-(1 -> 3)-alpha-D-Manp-(1 -> 5) structure in virulence.

  • 283.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Kovacs, Helena
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    NMR structure analysis of uniformly 13C-labeled carbohydrates2014Inngår i: Journal of Biomolecular NMR, ISSN 0925-2738, E-ISSN 1573-5001, Vol. 59, nr 2, s. 95-110Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this study, a set of nuclear magnetic resonance experiments, some of them commonly used in the study of C-13-labeled proteins and/or nucleic acids, is applied for the structure determination of uniformly C-13-enriched carbohydrates. Two model substances were employed: one compound of low molecular weight [(UL-C-13)-sucrose, 342 Da] and one compound of medium molecular weight (C-13-enriched O-antigenic polysaccharide isolated from Escherichia coli O142, similar to 10 kDa). The first step in this approach involves the assignment of the carbon resonances in each monosaccharide spin system using the anomeric carbon signal as the starting point. The C-13 resonances are traced using C-13-C-13 correlations from homonuclear experiments, such as (H)CC-CT-COSY, (H)CC-NOESY, CC-CT-TOCSY and/or virtually decoupled (H)CC-TOCSY. Based on the assignment of the C-13 resonances, the H-1 chemical shifts are derived in a straightforward manner using one-bond H-1-C-13 correlations from heteronuclear experiments (HC-CT-HSQC). In order to avoid the (1) J (CC) splitting of the C-13 resonances and to improve the resolution, either constant-time (CT) in the indirect dimension or virtual decoupling in the direct dimension were used. The monosaccharide sequence and linkage positions in oligosaccharides were determined using either C-13 or H-1 detected experiments, namely CC-CT-COSY, band-selective (H)CC-TOCSY, HC-CT-HSQC-NOESY or long-range HC-CT-HSQC. However, due to the short T-2 relaxation time associated with larger polysaccharides, the sequential information in the O-antigen polysaccharide from E. coli O142 could only be elucidated using the H-1-detected experiments. Exchanging protons of hydroxyl groups and N-acetyl amides in the C-13-enriched polysaccharide were assigned by using HC-H2BC spectra. The assignment of the N-acetyl groups with N-15 at natural abundance was completed by using HN-SOFAST-HMQC, HNCA, HNCO and C-13-detected (H)CACO spectra.

  • 284.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Li, Shengyu
    Yang, Zhennai
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies of the exopolysaccharide from Lactobacillus plantarum C88 using NMR spectroscopy and the program CASPER2015Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 402, s. 87-94Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Some lactic acid bacteria, such as those of the Lactobacillus genus, have the ability to produce exopolysaccharides (EPSs) that confer favorable physicochemical properties to food and/or beneficial physiological effects on human health. In particular, the EPS of Lactobacillus plantarum C88 has recently demonstrated in vitro antioxidant activity and, herein, its structure has been investigated using NMR spectroscopy and the computer program CASPER (Computer Assisted Spectrum Evaluation of Regular polysaccharides). The pentasaccharide repeating unit of the O-deacetylated EPS consists of a trisaccharide backbone, -> 4)-alpha-DGalp-(1 -> 2)-alpha-D-Glcp-(1 -> 3)-beta-D-Glcp-(1 ->, with terminal D-Glc and D-Gal residues (1.0 and 0.8 equiv per repeating unit, respectively) extending from O3 and O6, respectively, of the -> 4)-alpha-D-Galp-(1 -> residue. In the native EPS an O-acetyl group is present, 0.85 equiv per repeating unit, at O2 of the alpha-linked galactose residue; thus the repeating unit of the EPS has the following structure: -> 4)[beta-D-Glcp-(1 -> 3)][beta-D-Galp-(1 -> 6)]alpha-D-Galp2Ac-(1 -> 2)-alpha-D-Glcp-(1 -> 3)-beta-D-Glcp-(1 ->. These structural features, and the chain length (similar to 10(3) repeating units on average, determined in a previous study), are expected to play an important role in defining the physicochemical properties of the polymer.

  • 285.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lundborg, Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Rapid structural elucidation of polysaccharides employing predicted functions of glycosyltransferases and NMR data: Application to the O-antigen of Escherichia coli O592014Inngår i: Glycobiology, ISSN 0959-6658, E-ISSN 1460-2423, Vol. 24, nr 5, s. 450-457Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A computerized method that uses predicted functions of glycosyltransferases (GTs) in conjunction with unassigned NMR data has been developed for the structural elucidation of bacterial polysaccharides (PSs). In this approach, information about the action of GTs (consisting of possible sugar residues used as donors and/or acceptors, as well as the anomeric configuration and/or substitution position in the respective glycosidic linkages) is extracted from the Escherichia coli O-antigen database and is submitted, together with the unassigned NMR data, to the CASPER program. This time saving methodology, which alleviates the need for chemical analysis, was successfully implemented in the structural elucidation of the O-antigen PS of E. coli O59. The repeating unit of the O-specific chain was determined using the O-deacylated PS and has a branched structure, namely, -> 6)[alpha-d-GalpA3Ac/4Ac-(1 -> 3)]-alpha-d-Manp-(1 -> 3)-alpha-d-Manp-(1 -> 3)-beta-d-Manp-(1 -> 3)-alpha-d-GlcpNAc-(1 ->. The identification of the O-acetylation positions was efficiently performed by comparison of the H-1,C-13 HSQC NMR spectra of the O-deacylated lipopolysaccharide and the lipid-free PS in conjunction with chemical shift predictions made by the CASPER program. The side-chain d-GalpA residue carries one equivalent of O-acetyl groups at the O-3 and O-4 positions distributed in the LPS in a 3:7 ratio, respectively. The presence of O-acetyl groups in the repeating unit of the E. coli O59 PS is consistent with the previously proposed acetyltransferase WclD in the O-antigen gene cluster.

  • 286.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Lundborg, Magnus
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies and biosynthetic aspects of the o antigen polysaccharide from Escherichia coli o1742012Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 354, s. 102-105Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure of the repeating unit of the O-antigenic polysaccharide (PS) from Escherichia coli O174 has been determined. Component analysis together with H-1 and C-13 NMR spectroscopy experiments were employed to elucidate the structure. Inter-residue correlations were determined by H-1, C-13-heteronuclear multiple-bond correlation and H-1, H-1-NOESY experiments. The PS is composed of tetrasaccharide repeating units with the following structure: -> 4)-beta-D-GlcpA-(1 -> 3)-beta-D-Galp-(1 -> 3)-beta-D-GalpNAc-(1 -> vertical bar beta-D-GlcpNAc-(1 -> 2) Cross-peaks of low intensity were present in the NMR spectra consistent with a beta-D-GlcpNAc-(1 -> 2)-beta-D-GlcpA(1 -> structural element at the terminal part of the polysaccharide, which on average is composed of similar to 15 repeating units. Consequently the biological repeating unit has a 3-substituted N-acetyl-D-galactosamine residue at its reducing end.

  • 287.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Ramström, Kristoffer
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies of the O-antigen polysaccharide from Escherichia coli O115 and biosynthetic aspects thereof2013Inngår i: Glycobiology, ISSN 0959-6658, E-ISSN 1460-2423, Vol. 23, nr 3, s. 354-362Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure of the O-antigen polysaccharide (PS) of Escherichia coliO115 has been investigated using a combination of component analysis and 1D and 2D nuclear magnetic resonance (NMR) spectroscopy experiments. The repeating unit of the O-antigen was elucidated using the O-deacetylated PS and has the following branched pentasaccharide structure: →3)[β-L-Rhap-(1 → 4)]-β-D-GlcpNAc-(1 → 4)-α-D-GalpA-(1 → 3)-α-D-Manp-(1 → 3)-β-D-GlcpNAc-(1→. Cross-peaks of low intensity, corresponding to a β-L-Rhap-(1 → 4)-β-D-GlcpNAc-(1→ structural element, were present in the NMR spectra and attributed to the terminal part of the PS; this information defines the biological repeating unit of the O-antigen by having a 3-substituted N-acetyl-D-glucosamine (GlcNAc) residue at its reducing end. Analysis of the NMR spectra of the native PS revealed O-acetyl groups distributed over different positions of theL-Rhap residue (∼0.70 per repeating unit) as well as at O-2 and O-3 of the D-GalpA residue (∼0.03 and ∼0.25 per repeating unit, respectively), which is in agreement with the presence of two acetyltransferases previously identified in the O-antigen gene cluster (Wang Q, Ruan X, Wei D, Hu Z, Wu L, Yu T, Feng L, Wang L. 2010. Mol Cell Probes. 24:286–290.). In addition, the four glycosyltransferases initially identified in the O-antigen gene cluster of E. coli O115 were analyzed using BLAST, and the function of two of them predicted on the basis of similarities with glycosyltransferases from Shigella dysenteriae type 5 and 12, as well as E. coli O58 and O152.

  • 288.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Karolinska Institute.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Facile Structural Elucidation of Glycans Using NMR Spectroscopy Data and the Program CASPER: Application to the O-Antigen Polysaccharide of Escherichia coli O1552013Inngår i: ChemPlusChem, ISSN 2192-6506, Vol. 78, nr 11, s. 1327-1329Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The program CASPER was successfully employed to rapidly elucidate a new O-antigen polysaccharide structure (obtained from a strain of Escherichia coli serogroup O155), using solelyunassigned NMR spectroscopy data as input information. Thus, what is considered the most tedious and time-consuming part of the structural elucidation process has been reduced from several hours (or even days) of manual interpretation to about four minutes of automated analysis.

  • 289.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural Elucidation of the O-Antigen Polysaccharide from Escherichia coli O1812015Inngår i: ChemistryOpen, ISSN 2191-1363, Vol. 4, nr 1, s. 47-55Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Shiga-toxin-producing Escherichia coli (STEC) is an important pathogen associated to food-borne infection in humans; strains of E.coli O181, isolated from human cases of diarrhea, have been classified as belonging to this pathotype. Herein, the structure of the O-antigen polysaccharide (PS) from E.coli O181 has been investigated. The sugar analysis showed quinovosamine (QuiN), glucosamine (GlcN), galactosamine (GalN), and glucose (Glc) as major components. Analysis of the high-resolution mass spectrum of the oligosaccharide (OS), obtained by dephosphorylation of the O-deacetylated PS with aqueous 48% hydrofluoric acid, revealed a pentasaccharide composed of two QuiNAc, one GlcNAc, one GalNAc, and one Glc residue. The H-1 and (CNMR)-C-13 chemical shift assignments of the OS were carried out using 1D and 2D NMR experiments, and the OS was sequenced using a combination of tandem mass spectrometry (MS/MS) data and NMR (CNMR)-C-13 glycosylation shifts. The structure of the native PS was determined using NMR spectroscopy, and it consists of branched pentasaccharide repeating units joined by phosphodiester linkages: -> 4)[alpha-L-QuipNAc-(1 -> 3)]-alpha-D-GalpNAc6Ac-(1 -> 6)-alpha-D-Glcp-(1 -> P-4)-alpha-L-QuipNAc-(1 -> 3)-beta-D-GlcpNAc-(1 ->; the O-acetyl groups represent 0.4 equivalents per repeating unit. Both the OS and PSs exhibit rare conformational behavior since two of the five anomeric proton resonances could only be observed at an elevated temperature.

  • 290.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies and biosynthetic aspects of the O-antigen polysaccharide from Escherichia coli O422015Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 403, s. 174-181Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure of the O-antigen polysaccharide (PS) from Escherichia coli O42 has been investigated by NMR spectroscopy as the main method, which was complemented with sugar analysis, mass spectrometry, and analysis of biosynthetic information. The O-specific chain of the O-deacylated lipopolysaccharide (LPS-OH) consists of branched tetrasaccharide-glycerol repeating units joined by phosphodiester linkages. The lipid-free polysaccharide contains 0.8 equiv of O-acetyl groups per repeating unit and has the following teichoic acid-like structure: Based on biosynthetic aspects, this should also be the biological repeating unit. This O-antigen structure is remarkably similar to that of E. coli O28ac, differing only in the presence or absence, respectively, of a glucose residue at the branching point. The structural similarity explains the serological cross-reactivity observed between strains of these two serogroups, and also their almost identical O-antigen gene cluster sequences. -> 2)-(R)-Gro-(1-P-4)-beta-D-GlcpNAc-(1 -> 3)-beta-D-Galf2Ac-(1 -> 3)-alpha-D-GlcpNAc-(1 -> vertical bar a-D-Glcp-(1 -> 3)

  • 291.
    Fontana, Carolina
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Zaccheus, Mona V.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Weintraub, Andrej
    Ansaruzzaman, Mohammad
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural studies of a polysaccharide from Vibrio parahaemolyticus strain AN-160002016Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 432, s. 41-49Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure of a polysaccharide from Vibrio parahaemolyticus strain AN-16000 has been investigated. The sugar and absolute configuration analysis revealed D-Glc, D-GalN, D-QuiN and L-FucN as major components. The PS was subjected to dephosphorylation with aqueous 40% HF to obtain an oligosaccharide that was analyzed by H-1 and C-13 NMR spectroscopy. The HR-MS spectrum of the oligosaccharide revealed a pentasaccharide composed of two Glc residues, one QuiNAc and one GalNAc, one FucNAc, as well as a glycerol moiety. The structure of the PS was determined using H-1, C-13, N-15 and P-31 NMR spectroscopy; inter-residue correlations were identified by H-1, C-13-heteronuclear multiple-bond correlation, H-1, H-1-NOESY and H-1, P-31-hetero-TOCSY experiments. The PS backbone has the following teichoic acid-like structure: -> 3)-D-Gro-(1-P-6)-beta-D-Glcp-(1 -> 4)-alpha-L-FucpNAc-(1 -> 3)-beta-D-QuipNAc-(1 -> with a side-chain consisting of alpha-D-Glcp-(1 -> 6)-alpha-D-GalpNAc-(1 -> linked to the O3 position of the FucNAc residue.

  • 292. Foster, R. A.
    et al.
    Carlin, N. I. A.
    Majcher, M.
    Tabor, H.
    Ng, L.-K.
    Widmalm, Göran
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Structural elucidation of the O-antigen of the Shigella flexneri provisionalserotype 88-893: structural and serological similarities with S. flexneri provisional serotype Y394 (1c)2011Inngår i: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 346, nr 6, s. 872-876Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The structure of the repeating unit of the O-antigen polysaccharide from Shigella flexneri provisional serotype 88-893 has been determined. 1H and 13C NMR spectroscopy as well as 2D NMR experiments were employed to elucidate the structure. The carbohydrate part of the hexasaccharide repeating unit is identical to the previously elucidated structure of the O-polysaccharide from S. flexneri prov. serotype Y394. The O-antigen of S. flexneri prov. serotype 88-893 carries 0.7 mol O-acetyl group per repeating unit located at O-2 of the 3-substituted rhamnosyl residue, as identified by H2BC and BS-CT-HMBC NMR experiments. The O-antigen polysaccharide is composed of hexasaccharide repeating units with the following structure: →2)-α-l-Rhap-(1→2)-α-l-Rhap-(1→3)-α-l-Rhap2Ac-(1→3)[α-d-Glcp-(1→2)-α-d-Glcp-(1→4)]-β-d-GlcpNAc-(1→. Serological studies showed that type antigens for the two provisional serotypes are identical; in addition 88-893 expresses S. flexneri group factor 6 antigen. We propose that provisional serotypes Y394 and 88-893 be designated as two new serotypes 7a and 7b, respectively, in the S. flexneri typing scheme.

  • 293. Fourniere, Viviane
    et al.
    Skantz, Linnea
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Sajtos, Ferenc
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Oscarson, Stefan
    Lahmann, Martina
    Synthesis of the Lewis b pentasaccharide and a HSA-conjugate thereof2010Inngår i: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 66, nr 39, s. 7850-7855Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Helicobacter pylori, a gastric pathogen, binds to various blood group antigens, including the Lewis types, present in the gastric tissue and a relation between the presentation of the ligands and the overall strength of binding has been assumed. Synthetic Lewis b tetra- and hexasaccharide conjugates are available but not the analogous pentasaccharide. An efficient synthesis of the amino spacer equipped Lewis b pentasaccharide, 3-aminopropyl alpha-L-fucopyranosyl-(1 -> 2)-beta-D-galactopyranosyl-(1 3)-[alpha-L-fucopyranosyl-(1 -> 4)]-2-acetamido-2-deoxy-beta-D-glucopyranosyl-(1 -> 3)-beta-D-galactopyranoside, is presented to enable further investigation of the carbohydrate recognition process of H. pylori.

  • 294.
    Fournière, Viviane
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Cumpstey, Ian
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Synthesis of non-glycosidically linked selenoether pseudodisaccharides2010Inngår i: Tetrahedron Letters, ISSN 0040-4039, E-ISSN 1359-8562, Vol. 51, nr 16, s. 2127-2129Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Non-glycosidically linked disaccharide mimetics with a selenoether functionality linking the two monosaccharide residues have been synthesised. Protected Glc(Se3–3)Glc, Glc(Se3–6)Glc and Glc(Se3–6)Man structures were obtained. Selenium was introduced by displacement of carbohydrate sulfonates with a selenobenzoate anion. Conversion into diselenides by methanolysis of the benzoate and aerial oxidation was followed by reduction of the diselenides to selenolates, and in situ displacement of a second carbohydrate sulfonate in an SN2 reaction to give selenoethers. Glc(Se3–3)Glc and Glc(Se3–6)Glc were also obtained in deprotected form.

  • 295. Francois, Camille
    et al.
    Pourchet, Sylvie
    Boni, Gilles
    Fontaine, Stephane
    Gaillard, Yves
    Placet, Vincent
    Galkin, Maxim V.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Orebom, Alexander
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Samec, Joseph
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Plasseraud, Laurent
    Diglycidylether of iso-eugenol: a suitable lignin-derived synthon for epoxy thermoset applications2016Inngår i: RSC Advances, ISSN 2046-2069, E-ISSN 2046-2069, Vol. 6, nr 73, s. 68732-68738Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A novel lignin-based synthon, diglycidylether of iso-eugenol (DGE-isoEu) is used as a prepolymer for the preparation of thermosetting resins. DGE-isoEu is synthesized in a two-step procedure with a satisfactory yield from bio-based iso-eugenol (isoEu, 2-methoxy-4-(1-propenyl)phenol) catalytically fragmented from lignin in an organosolv process. DGE-isoEu was fully characterized by NMR, MS and FTIR. Curing of the DGE-isoEu monomer has then been investigated in the presence of several carboxylic acid derivatives hardeners. The thermal and mechanical properties of each material were recorded showing, in particular, a high T-g and instantaneous modulus values in the range of 78-120 degrees C and 4.6-5.5 GPa, respectively. The lignin derived new materials give very attractive thermo-mechanical properties comparable to that of common BPA-containing epoxy resins.

  • 296.
    Fransson, Ann-Britt L.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Borén, Linnéa
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Pàmies, Oscar
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Kinetic Resolution and Chemoenzymatic Dynamic Kinetic Resolution of Functionalized γ-Hydroxy Amides2005Inngår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 70, nr 7, s. 2582-2587Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An efficient kinetic resolution of racemic gamma-hydroxy amides 1 was performed via Pseudomas cepacia lipase (PS-C)-catalyzed transesterification. The enzyme PS-C tolerates both variation in the chain length and different functionalities giving good to high enantioselectivity (E values of up to > 250). The combination of enzymatic kinetic resolution with a ruthenium-catalyzed racemization led to a dynamic kinetic resolution. The use of 2,4-dimethyl-3-pentanol as a hydrogen source to suppress ketone formation in the dynamic kinetic resolution yields the corresponding acetates in good yield and good to high enantioselectivity (ee's up to 98%). The synthetic utility of this procedure was illustrated by the practical synthesis of the versatile intermediate gamma-lactone (R)-5-methyltetrahydrofuran-2-one.

  • 297.
    Fransson, Ann-Britt L.
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Xu, Yongmei
    Leijondahl, Karin
    Bäckvall, Jan-Erling
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Enzymatic Resolution, Desymmetrization and Dynamic Kinetic Asym-metric Transformation of 1,3-Cycloalkanediols2006Inngår i: Journal of Organic Chemistry, ISSN 0022-3263, E-ISSN 1520-6904, Vol. 71, nr 17, s. 6309-6316Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    An efficient desymmetrization of cis-1,3-cyclohexanediol to (1S,3R)-3-(acetoxy)-1-cyclohexanol ((R,S)-2a) was performed via Candida antarctica lipase B (CALB)-catalyzed transesterification, in high yield (up to 93%) and excellent enantioselectivity (ee's up to >99.5%). (R,R)-Diacetate ((R,R)-3a) was obtained in a DYKAT process at room temperature from (1S,3R)-3-acetoxy-1-cyclohexanol ((R,S)-2a), in a high trans/cis ratio (91:9) and in excellent enantioselectivity of >99%. Metal- and enzyme-catalyzed dynamic transformation of cis/trans-1,3-cyclohexanediol using PS-C gave a high diastereoselectivity for cis-diacetate (cis/trans = 97:3). The (1R,3S)-3-acetoxy-1-cyclohexanol (ent-(R,S)-2a) was obtained from cis-diacetate by CALB-catalyzed hydrolysis in an excellent yield (97%) and selectivity (>99% ee). By deuterium labeling it was shown that intramolecular acyl migration does not occur in the transformation of cis-monoacetate to the cis-diacetate.

  • 298. Fransson, Ann-Britt
    et al.
    Xu, Yongmei
    Leijondahl, Karin
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan-Erling
    Enzymatic resolution, desymmetrization and dynamic kinetic asymmetric transformation of 1,3-cycloalkanediols2006Inngår i: Journal of organic chemistry, ISSN 0022-3263, Vol. 71, nr 17, s. 6309-6316Artikkel i tidsskrift (Fagfellevurdert)
  • 299.
    Franzén, Johan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Bäckvall, Jan E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Carbon-Carbon bond formation in Palladium(II)-Catalyzed Allylic Oxidation: A Novel Oxidative Carbozyclization of Allene-Substituted Olefins2003Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 125, nr 20, s. 6056-6057Artikkel i tidsskrift (Fagfellevurdert)
  • 300.
    Franzén, Johan
    et al.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Löfstedt, Joakim
    Dorange, Ismet
    Bäckvall, Jan E.
    Stockholms universitet, Naturvetenskapliga fakulteten, Institutionen för organisk kemi.
    Allenes as Carbon Nucleophiles in Palladium-Catalyzed Reactions: Observation of anti Attack of Allenes on (p-Allyl)Palladium Complexes2002Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 124, nr 38, s. 11246-11247Artikkel i tidsskrift (Fagfellevurdert)
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