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  • 1.
    Berthold, Malin
    Stockholm University, Faculty of Science.
    Galanin: ligand - receptor interactions1997Doctoral thesis, comprehensive summary (Other academic)
  • 2. Cervin, Nicholas T.
    et al.
    Andersson, Linnea
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Ng, Jovice Boon Sing
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Olin, Pontus
    Bergström, Lennart
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Wågberg, Lars
    Lightweight and Strong Cellulose Materials Made from Aqueous Foams Stabilized by Nanofibrillated Cellulose2013In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 14, no 2, p. 503-511Article in journal (Refereed)
    Abstract [en]

    A lightweight and strong porous cellulose material has been prepared by drying aqueous foams stabilized with surface-modified nanofibrillated cellulose (NFC). This material differs from other dry, particle stabilized foams in that renewable cellulose is used as stabilizing particles. Confocal microscopy and high speed video imaging show that the octylamine-coated, rod-shaped NFC nanoparticles residing at the air-liquid interface prevent the air bubbles from collapsing or coalescing. Stable wet foams can be achieved at solids content around 1% by weight. Careful removal of the water results in a cellulose-based material with a porosity of 98% and a density of 30 mg cm(-3). These porous cellulose materials have a higher Young's modulus than porous cellulose materials made from freeze-drying, at comparable densities, and have a compressive energy absorption of 56 kJ m(-3) at 80% strain. Measurement with the aid of an autoporosimeter revealed that most pores are in the range of 300 to 500 mu m.

  • 3.
    Fontana, Carolina
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Conde-Alvarez, Raquel
    Ståhle, Jonas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Holst, Otto
    Iriarte, Maite
    Zhao, Yun
    Arce-Gorvel, Vilma
    Hanniffy, Sean
    Gorvel, Jean-Pierre
    Moriyon, Ignacio
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structural Studies of Lipopolysaccharide-defective Mutants from Brucella melitensis Identify a Core Oligosaccharide Critical in Virulence2016In: Journal of Biological Chemistry, ISSN 0021-9258, E-ISSN 1083-351X, Vol. 291, no 14, p. 7727-7741Article in journal (Refereed)
    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.

  • 4.
    Fontana, Carolina
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Kovacs, Helena
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    NMR structure analysis of uniformly 13C-labeled carbohydrates2014In: Journal of Biomolecular NMR, ISSN 0925-2738, E-ISSN 1573-5001, Vol. 59, no 2, p. 95-110Article in journal (Refereed)
    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.

  • 5.
    Fontana, Carolina
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Lundborg, Magnus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structural studies and biosynthetic aspects of the o antigen polysaccharide from Escherichia coli o1742012In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 354, p. 102-105Article in journal (Refereed)
    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.

  • 6.
    Liao, Rong-Zhen
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry. Huazhong University of Science & Technology, People's Republic of China.
    Siegbahn, Per E. M.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mechanism for O-O bond formation in a biomimetic tetranuclear manganese cluster - A density functional theory study2015In: Journal of Photochemistry and Photobiology. B: Biology, ISSN 1011-1344, E-ISSN 1873-2682, Vol. 152, no Part A, p. 162-172Article in journal (Refereed)
    Abstract [en]

    Density functional theory calculations have been used to study the reaction mechanism of water oxidation catalyzed by a tetranuclear Mn-oxo cluster Mn4O4L6 (L = (C6H4)(2)PO4-). It is proposed that the O-O bond formation mechanism is different in the gas phase and in a water solution. In the gas phase, upon phosphate ligand dissociation triggered by light absorption, the O-O bond formation starting with both the Mn-4(III,III,IV,IV) and Mn-4(III,IV,IV,IV) oxidation states has to take place via direct coupling of two bridging oxo groups. The calculated barriers are 42.3 and 37.1 kcal/mol, respectively, and there is an endergonicity of more than 10 kcal/mol. Additional photons are needed to overcome these large barriers. In water solution, water binding to the two vacant sites of the Mn ions, again after phosphate dissociation triggered by light absorption, is thermodynamically and kinetically very favorable. The catalytic cycle is suggested to start from the Mn-4(III,III,III,IV) oxidation state. The removal of three electrons and three protons leads to the formation of a Mn-4(III,IV,IV,IV)-oxyl radical complex. The O-O bond formation then proceeds via a nucleophilic attack of water on the Mn-IV-oxyl radical assisted by a Mn-bound hydroxide that abstracts a proton during the attack. This step was calculated to be rate-limiting with a total barrier of 29.2 kcal/mol. This is followed by proton-coupled electron transfer, O-2 release, and water binding to start the next catalytic cycle.

  • 7.
    Lundborg, Magnus
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Fontana, Carolina
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Automatic structure determination of regular polysaccharides based solely on NMR spectroscopy2011In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 12, no 11, p. 3851-3855Article in journal (Refereed)
    Abstract [en]

    The structural analysis of polysaccharides requires that the sugar components and their absolute configurations are determined. We here show that this can be performed based on NMR spectroscopy by utilizing butanolysis with (+)- and (-)-2-butanol that gives the corresponding 2-butyl glycosides with characteristic 1H and 13C NMR chemical shifts. The subsequent computer-assisted structural determination by CASPER can then be based solely on NMR data in a fully automatic way as shown and implemented herein. The method is additionally advantageous in that reference data only have to be prepared once and from a user's point of view only the unknown sample has to be derivatized for use in CASPER.

  • 8. Mally, Manuela
    et al.
    Fontana, Carolina
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    LeibundGut-Landmann, Salome
    Laacisse, Lamia
    Fan, Yao-Yun
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Aebi, Markus
    Glycoengineering of host mimicking type-2 LacNAc polymersand Lewis X antigens on bacterial cell surfaces2013In: Molecular Microbiology, ISSN 0950-382X, E-ISSN 1365-2958, Vol. 87, no 1, p. 112-131Article in journal (Refereed)
    Abstract [en]

    Bacterial carbohydrate structures play a central role in mediating a variety of host-pathogen interactions. Glycans can either elicit protective immune response or lead to escape of immune surveillance by mimicking host structures. Lipopolysaccharide (LPS), a major component on the surface of Gram-negative bacteria, is composed of a lipid A-core and the O-antigen polysaccharide. Pathogens like Neisseria meningitidis expose a lipooligosaccharide (LOS), which outermost glycans mimick mammalian epitopes to avoid immune recognition. Lewis X (Gal beta 1-4(Fuc alpha 1-3)GlcNAc) antigens of Helicobacter pylori or of the helminth Schistosoma mansoni modulate the immune response by interacting with receptors on human dendritic cells. In a glycoengineering approach we generate human carbohydrate structures on the surface of recombinant Gram-negative bacteria, such as Escherichia coli and Salmonella enterica sv. Typhimurium that lack O-antigen. A ubiquitous building block in mammalian N-linked protein glycans is Gal beta 1-4GlcNAc, referred to as a type-2 N-acetyllactosamine, LacNAc, sequence. Strains displaying polymeric LacNAc were generated by introducing a combination of glycosyltransferases that act on modified lipid A-cores, resulting in efficient expression of the carbohydrate epitope on bacterial cell surfaces. The poly-LacNAc scaffold was used as an acceptor for fucosylation leading to polymers of Lewis X antigens. We analysed the distribution of the carbohydrate epitopes by FACS, microscopy and ELISA and confirmed engineered LOS containing LacNAc and Lewis X repeats by MALDI-TOF and NMR analysis. Glycoengineered LOS induced pro-inflammatory response in murine dendritic cells. These bacterial strains can thus serve as tools to analyse the role of defined carbohydrate structures in different biological processes.

  • 9.
    Runquist, Mårten
    Stockholm University, Faculty of Science.
    Distribution and regulation of enzymes involved in polyisoprenoid biosynthesis1995Doctoral thesis, comprehensive summary (Other academic)
  • 10. Wangsell, Fredrik
    et al.
    Nordeman, Patrik
    Savmarker, Jonas
    Emanuelsson, Rikard
    Jansson, Katarina
    Lindberg, Jimmy
    Rosenquist, Asa
    Samuelsson, Bertil
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Larhed, Mats
    Investigation of alpha-phenylnorstatine and alpha-benzylnorstatine as transition state isostere motifs in the search for new BACE-1 inhibitors2011In: Bioorganic & Medicinal Chemistry, ISSN 0968-0896, E-ISSN 1464-3391, Vol. 19, no 1, p. 145-155Article in journal (Refereed)
    Abstract [en]

    Inhibition of the BACE-1 protease enzyme has over the recent decade developed into a promising drug strategy for Alzheimer therapy. In this report, more than 20 new BACE-1 protease inhibitors based on alpha-phenylnorstatine, alpha-benzylnorstatine, iso-serine, and beta-alanine moieties have been prepared. The inhibitors were synthesized by applying Fmoc solid phase methodology and evaluated for their inhibitory properties. The most potent inhibitor, tert-alcohol containing (R)-12 (IC(50) = 0.19 mu M) was co-crystallized in the active site of the BACE-1 protease, furnishing a novel binding mode in which the N-terminal amine makes a hydrogen bond to one of the catalytic aspartic acids.

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