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  • 1.
    Abbasi, Alireza
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lindqvist-Reis, Patric
    Eriksson, Lars
    Sandström, Dick
    Lidin, Sven
    Persson, Ingmar
    Sandström, Magnus
    Highly hydrated cations: Deficiency, mobility and coordination of water in crystalline nonahydrated scandium(III), yttrium(III) and lanthanoid(III) trifluoromethanesulfonate2005In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 11, no 14, p. 4065-4077Article in journal (Refereed)
    Abstract [en]

    Trivalent lanthanide-like metal ions coordinate nine water oxygen atoms, which form a tricapped trigonal prism in a large number of crystalline hydrates. Water deficiency, randomly distributed over the capping positions, was found for the smallest metal ions in the isomorphous nonahydrated trifluoromethanesulfonates, [M(H2O)(n)]CF3SO3)(3), in which M=Sc-III, Lu-III, Yb-III, Tm-III or Er-III. The hydration number n increases (n=8.0(1), 8.4(1), 8.7(1), 8.8(1) and 8.96(5), respectively) with increasing ionic size. Deuterium (H-2) solid-state NMR spectroscopy revealed fast positional exchange between the coordinated capping and prism water molecules; this exchange started at temperatures higher than about 280 K for lutetium(m) and below 268 K for scandium(m). Similar positional exchange for the fully nonahydrated yttrium(m) and lanthanum(m) compounds started at higher temperatures, over about 330 and 360 K, respectively. An exchange mechanism is proposed that can exchange equatorial and capping water molecules within the restrictions of the crystal lattice, even for fully hydrated lanthanoid(III) ions. Phase transitions occurred for all the water-deficient compounds at; 185 K. The hydrated scandium(III) trifluoromethanesulfonate transforms reversibly (Delta H degrees= -0.80(1) kJ mol(-1) on cooling) to a trigonal unit cell that is almost nine times larger, with the scandium ion surrounded by seven fully occupied and two partly occupied oxygen atom positions in a distorted capped trigonal prism. The hydrogen bonding to the trifluoromethanesulfonate anions stabilises the trigonal prism of water ligands, even for the crowded hydration sphere of the smallest metal ions in the series. Implications for the Lewis acid catalytic activity of the hydrated scandium(III) and lanthanoid(III) trifluoromethanesulfonates for organic syntheses performed in aqueous media are discussed.

  • 2.
    Aydin, Juhanes
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Senthil, Kumar K
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sayah, Mahmoud J
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Wallner, Olov A
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán J
    Synthesis and catalytic application of chiral 1,1'-Bi-2-naphthol- and biphenanthrol-based pincer complexes: selective allylation of sulfonimines with allyl stannane and allyl trifluoroborate.2007In: Journal of Organic Chemistry, Vol. 72, no 13, p. 4689-4697Article in journal (Refereed)
    Abstract [en]

    New easily accessible 1,1'-bi-2-naphthol- (BINOL-) and biphenanthrol-based chiral pincer complex catalysts were prepared for selective (up to 85% enantiomeric excess) allylation of sulfonimines. The chiral pincer complexes were prepared by a flexible modular approach allowing an efficient tuning of the selectivity of the catalysts. By employment of the different enantiomeric forms of the catalysts, both enantiomers of the homoallylic amines could be selectively obtained. Both allyl stannanes and allyl trifluoroborates can be employed as allyl sources in the reactions. The biphenanthrol-based complexes gave higher selectivity than the substituted BINOL-based analogues, probably because of the well-shaped chiral pocket generated by employment of the biphenanthrol complexes. The enantioselective allylation of sulfonimines presented in this study has important implications for the mechanism given for the pincer complex-catalyzed allylation reactions, confirming that this process takes place without involvement of palladium(0) species.

  • 3.
    Aydin, Juhanes
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium-pincer complex catalyzed C-C coupling of allyl nitriles with tosyl imines via regioselective allylic C-H bond functionalization2008In: Organic Letters, ISSN 1523-7060, Vol. 10, no 13, p. 2881-2884Article in journal (Refereed)
    Abstract [en]

    A mechanistically new palladium-pincer complex catalyzed allylation of sulfonimines is presented. This reaction involves C-H bond functionalization of allyl nitriles under mild conditions. The reaction proceeds with a high regioselectivity, without allyl rearrangement of the product. Modeling studies indicate that the carbon-carbon bond formation process proceeds via (η1-allyl)palladium pincer complex intermediates.

  • 4.
    Becker, Richard
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Berger, Helmuth
    Crystal Structure of the New Cobalt Tellurite Chloride Co5Te4O11Cl42007In: Zeitschrift für Anorganische und Allgemeines Chemie, ISSN 0044-2313, E-ISSN 1521-3749, Vol. 633, no 3, p. 422-424Article in journal (Refereed)
    Abstract [en]

    The crystal structure of the new compound Co5Te4O11Cl4 is described. It crystallizes in the triclinic system, space group P-1 with the unit cell parameters a = 822.26(8) pm, b = 1029.7(1) pm, c = 1031.1(1) pm, = 110.80(1)°, β = 97.950(9)°, = 98.260(9)° and Z = 2. The structure is layered along the bc–plane and built by [CoO5Cl], [CoO4Cl2] and [CoO4Cl] polyhedra sandwiched by [TeO3E] and [TeO4E] polyhedra. The layers can be regarded as infinite molecules without any net charge and only weak van der Waals forces connect them to each other. The halides and the lone-pair, E, of TeIV protrude from the layers.

  • 5.
    Bergström, Lennart
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Sörensen, Malin H
    Boon Sing Ng, Jovice
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Alberius, Peter C.A.
    Improved enzymatic activity of Thermomyces lanuginosus lipase immobilized in a hydrophobic particulate mesoporous carrier2010In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 343, p. 359-365Article in journal (Other academic)
    Abstract [en]

    Lipase from Thermomyces lanuginosus has been immobilized within particulate mesoporous silica carriers, with either hydrophilic or hydrophobic supporting surfaces, produced by the newly developed emulsion and solvent evaporation (ESE) method. The Michaelis–Menten model was used to calculate the parameters related to the enzymatic activity of lipase i.e. the turnover number, kcat, and the specific activity. The specific activity was improved by immobilization of lipase onto the hydrophobic support, compared to lipase immobilized onto the hydrophilic support and lipase free in solution. The enhanced enzymatic activity of lipase onto a hydrophobic support was attributed to interfacial activation of the Thermomyces lanuginosus lipase when it is attached to a hydrophobic surface and a reduced denaturation. Confocal scanning laser microscopy (CLSM) studies, of fluorescently tagged lipase, showed that leakage of the lipase from the mesoporous particles was limited to an initial period of only a few hours. Both the rate and the amount of lipase leached were reduced when the lipase was immobilized onto the hydrophobic support.

  • 6.
    Bielawski, Marcin
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Efficient one-pot synthesis of bis(4-tert-butylphenyl)iodonium triflate2009In: Organic Syntheses, ISSN 0078-6209, Vol. 86, p. 308-314Article in journal (Refereed)
  • 7.
    Björling, Thomas
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Synthesis and characterisation of Zintl hydrides2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The synthesis, structural characterisation and the properties of the Zintl hydrides AeE2H2 and AeAlSiH (Ae = Ba, Ca, Sr; E = Al, Ga, In, Si, Zn) are reported. The first hydride in this class of compounds is SrAl2H2 which was discovered under an experiment by Gingl, who hydrogenated SrAl2 at various temperatures. (Gingl et al, Journal of Alloys and Compounds 306 (2000) 127-132). The intention was to form alanates, e.g. AlH4-, by terminating the three dimensional four connected aluminium network in SrAl2. The new hydride, SrAl2H2, has a partially conserved aluminium network. The three dimensional anionic network in SrAl2 is reduced to two dimensions in the hydride, with aluminium bonded to both aluminium and hydrogen. This type of bonding configuration has not been observed before.

    The hydrogenation of SrAl2 is straight forward, 190 oC and 50 bar, compared to the difficult synthesis of alanates and alane, AlH3. The latter synthesises uses aluminium in its zero oxidation state in contrast to the synthesis of SrAl2H2 from SrAl2. (In the SrAl2-precursor aluminium is reduced by the electropositive metal to -I.) Thus, the discovery shows a different route to alanates by using precursors with aluminium in a reduced state. If SrAl2H2 is further hydrogenated at 250 oC the two dimensional network breaks and Sr2AlH7 forms.

    We wanted to investigate if SrAl2H2 was a singularity or if other similar compounds exist. We wanted to study how hydrogenation of precursors similar to the aluminide result in 1) new routes to compounds with high hydrogen content, as alanates, 2) to investigate how the E-H bond is affected as function of the network composition among different ternary hydrides, in particular BaAlxSi2-xHx, and choice of active metal.

    BaGa2H2 and SrGa2H2, two hydrides isostructural with SrAl2H2, were synthesized from its precursors BaGa2 and SrGa2. In addition three ternary hydrides BaAlSiH, CaAlSiH and SrAlSiH were manufactured from their related AeAlSi precursors.

    All powders were characterized by neutron and x-ray diffraction methods.

    An increased stability towards water/moisture compared to ordinary saline hydrides was noticed, especially for the ternary hydrides. Heat stability was measured with DSC (differential scanning calorimetry). The hydrides BaGa2H2 and SrGa2H2 decompose around 300 oC at 1 atm. This is similar to isostructural SrAl2H2. The ternary hydrides BaAlSiH and SrAlSiH decompose at 600 oC, at 1 atm, which is the highest noticed temperature for compounds with Al-H bonds. Inelastic neutron scattering experiments showed that these hydrides Al-H and Sr-H bonds are really weak, even weaker then the Al-H interactions in alanates and alanes. These hydrides are probably stabilized be their lattices. The electric properties among the ternary hydrides were measured with IR-spectroscopy (diffuse reflectance). The ternary hydrides, AeAlSiH, are indirect semi conductors. BaGa2H2 and SrGa2H2 are conductors. The ternary hydrides, AeAlxSi2-xHx, may have adjustable band gaps, which we were not able to determine.

    This work is leading into a new research area within the field of metal hydrides.

  • 8.
    Blomqvist, Helen
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Magnesium ions stabilizing solid-state transition metal hydrides2003Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is focused on hydrides containing first-row transition metal–hydrido complexes counterbalanced by magnesium. In particular, fundamental properties of the promising hydrogen storage material Mg2NiH4 have been studied. Results presented in the thesis provide detailed knowledge of the electronic structure and bonding mechanisms and are of significance for improving the hydrogen desorption process of complex transition metal hydrides in general.Two competing stabilization mechanisms in Mg2NiH4 have been identified; presence of microtwinning in the structure and the extra Mg added to the melt-cast Mg2Ni starting alloys, which acts as stabilizing dopant in the Mg2NiH4 system. When eliminating both stabilization mechanisms, the hydrogen release pressure was doubled at 453 K. Mg2NiH4 behaves like a heavily doped semiconductor at lower temperatures, but the conductivity is counteracted by the introduction of microtwinning in the structure at elevated temperatures, which makes the hydride non-conducting at » 400 K. The conductivity can be regained by reducing the amount of microtwinning with an applied mechanical pressure. Size, coordination and type of cation framework have decisive roles in determining the structure type of complex metal hydrides, as shown by ab initio total-energy calculations. Compared to the rich variety of Pd-based complex hydrides, the few Ni hydrido complexes hitherto found only contain Mg2+, solely or in combination with Ca2+, Sr2+, Yb2+, Eu2+ or La3+. Apparently the rather weak Ni–H bond needs a small and polarizing cation, e.g. Mg2+, to be stabilized in the solid state. The rather strong Mg–H interaction makes Mg2NiH4 a hybrid of ionic and complex transition metal hydride. This stabilization mechanism where electron density is redistributed by the polarizable hydrido ligand explains why Mg2NiH4 is very sensitive to disturbances of the crystal ordering, e.g. doping and ball milling, which profoundly affect stability, conductivity, color, structure and phasetransition conditions. Mg2+ also has the ability to stabilize Mn hydrido complexes, as observed in the novel Mg3MnH~6 compound, synthesized at GPa pressure in the solid state.

  • 9. Cribiù, Riccardo
    et al.
    Borbas, K. Eszter
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Cumpstey, Ian
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    On the synthesis of vinyl and phenyl C-furanosides by stereospecific debenzylative cycloetherification2009In: Tetrahedron, ISSN 0040-4020, E-ISSN 1464-5416, Vol. 65, no 10, p. 2022-2031Article in journal (Refereed)
  • 10.
    Córdova, Armando
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Ibrahem, Ismail
    Casas, Jesús
    Sundén, Henrik
    Engqvist, Magnus
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Reyes, Efraim
    Amino Acid-Catalyzed Neogenesis of Carbohydrates: A Plausible Ancient Transformation2005In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 11, no 16, p. 4772-4784Article in journal (Refereed)
    Abstract [en]

    Hexose sugars play a fundamental role in vital biochemical processes and their biosynthesis is achieved through enzyme-catalyzed pathways. Herein we disclose the ability of amino acids to catalyze the asymmetric neogenesis of carbohydrates by sequential cross-aldol reactions. The amino acids mediate the asymmetric de novo synthesis of natural L- and D-hexoses and their analogues with excellent stereoselectivity in organic solvents. In some cases, the four new stereocenters are assembled with almost absolute stereocontrol. The unique feature of these results is that, when an amino acid is employed as the catalyst, a single reaction sequence can convert a protected glycol aldehyde into a hexose in one step. For example, proline and its derivatives catalyze the asymmetric neogenesis of allose with >99 % ee in one chemical manipulation. Furthermore, all amino acids tested catalyzed the asymmetric formation of natural sugars under prebiotic conditions, with alanine being the smallest catalyst. The inherent simplicity of this catalytic process suggests that a catalytic prebiotic “gluconeogenesis” may occur, in which amino acids transfer their stereochemical information to sugars. In addition, the amino acid catalyzed stereoselective sequential cross-aldol reactions were performed as a two-step procedure with different aldehydes as acceptors and nucleophiles. The employment of two different amino acids as catalysts for the iterative direct aldol reactions enabled the asymmetric synthesis of deoxysugars with >99 % ee. In addition, the direct amino acid catalyzed C2+C2+C2 methodology is a new entry for the short, highly enantioselective de novo synthesis of carbohydrate derivatives, isotope-labeled sugars, and polyketide natural products. The one-pot asymmetric de novo syntheses of deoxy and polyketide carbohydrates involved a novel dynamic kinetic asymmetric transformation (DYKAT) mediated by an amino acid.

  • 11.
    Dahl, Leif
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Preparation and characterisation of perovskite and noble metal promoted oxide based catalysts1997Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This work concerns efforts to improve or replace noble-metal based catalysts used for car exhaust purification.

    Various oxide based catalysts have been prepared by impregnating washcoats such as (-Al2O3 and SiO2 with appropriate metal ions, and assemblies calcinated at elevated temperatures have been tested for catalytic activity in the oxidation of CO and C3H6 and reduction of NO. SEM-EDS, ATEM-EDS and XRD have been used for phase analysis and for studies of the morphology of catalysts prepared in situ. The perovskite compounds La1-xSrxMe1-2yCuyRuyO3 with Me = Al and Ga have been prepared, in situ and ex situ [SGIW1]respectively, and tested for catalytic activity. Changes in cell parameters and catalytic activity of in-situ LaAl1-xCuxO3 when exposed alternatingly to oxidising and reducing car exhaust atmospheres have been studied. The catalytic activity of various transition metal oxides with and without addition of Pt/Rh or Pd have also been tested.

  • 12.
    Dziedzic, Pawel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Amino acid-catalyzed synthesis of amino acid derivatives: Application and semi-synthesis of Paclitaxel, Docetaxel and their derivatives2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis deals with different applications of organocatalysis, where amino acid derivatives and small peptides are applied as catalysts. First, the development of environmentally friendly aldol reactions, carried out in aqueous media is illustrated. The corresponding β-hydroxy ketones are formed with ee´s up to 99%. Chapter 3 describes the ability of β3-amino acids to selectively catalyze Mannich-type reactions and govern the formation of products with high anti-selectivity (up to >19:1) and ee´s up to 99%. In the following chapter, an amino acid-catalyzed one-pot three component Mannich reaction between dihydroxyacetone and PMP-protected imines, is presented. The corresponding a,a’-dihydroxy-b-aminoketones are obtained in high yields and with 82-95% ee. Next, an aza-Morita-Baylis-Hillman reaction was investigated where L-proline is the catalyst. The reaction proceeds with excellent chemo- and enantioselectivity to give the corresponding compounds in good yields and with 97-99% ee. Finally, the last part describes development of a proline-catalyzed Mannich reation between N-acyl imines and protected α-hydroxyaldehyes, providing access to different α-hydroxy-β-amino acids in good yields and high enantioselctivity (92-99% ee). The obtained amino acids were further applied in the semisynthesis of paclitaxel and docetaxel derivatives.

  • 13.
    Dziedzic, Pawel
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Weibiao, Zou
    Hafrén, Jonas
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    The small peptide-catalyzed direct asymmetric aldol reaction in water2006In: Organic and biomolecular chemistry, ISSN 1477-0520, E-ISSN 1477-0539, Vol. 4, p. 38-40Article in journal (Refereed)
  • 14.
    Dziedzic, Pawel
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Zhao, Gui-ling
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Córdova, Armando
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Practical amino acid-catalyzed asymmetric synthesis pf protected α-hydroxy-amino aldehydes and acidsManuscript (preprint) (Other academic)
  • 15.
    Eriksson, Johan
    et al.
    Stockholm University, Faculty of Science, Department of Environmental Chemistry.
    Eriksson, Lars
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Department of Structural Chemistry.
    Jakobsson, Eva
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry, Department of Structural Chemistry.
    Decabromodiphenyl ether1999In: Acta crystallographica Section C, ISSN 0108-2701, Vol. 55, no 12, p. 2169-2171Article in journal (Refereed)
    Abstract [en]

    Bis(pentabromophenyl) ether, C12Br100, shows strangedifferences in the endocyclic angles between the twodifferent rings, although they are both substituted inthe same manner. Several short van der Waals contact distances give clues to the anomalous endocyclic anglesand some hints to the formation of decompositionproducts. We suggest that the intermolecular Br...Brcontacts contribute to the distortions of the ring systems.Usually distortions of this kind would be explained fromhighly anisotropic TLS behaviour, but the data from thetitle compound do not show any conclusive TLS effects.

  • 16.
    Fors, Yvonne
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Egsgaard, Helge
    Wickholm, Kristina
    Ammonia Treatment of Acidic Vasa Wood2009In: Proceedings 10th ICOM-CC WOAM Conference, Amsterdam 2007 / [ed] Per Hoffmann, Bremerhaven, 2009, p. 539-561Conference paper (Other academic)
    Abstract [en]

    Outbreaks of acidic sulfate salts have been reported in numerous areas on the wooden surfaces of the Swedish historical shipwreck Vasa (from 1628) in the Vasa Museum. Effects of ammonia vapour treatment to reduce the acidity in Vasa wood, similar to that previously applied to the Dutch East Indiaman Batavia (from 1629), have been investigated by means of solid state 13C-NMR and MALDI-TOF spectrometry. No major changes were found in the molecular weight distribution of the bulking agent polyethylene glycol (PEG) or in the crystallinity of pulp cellulose after mild exposure to ammonia vapour. Further studies on the long-term pH stability and the post-treatment properties of the wood using spectroscopic methods and mechanical testing are in progress.

  • 17.
    Fredrickson, Rie Takagi
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Johnsson, Mats
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Lidin, Sven
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Single-Crystal X-ray Study of Ba2Cu2Te4O11Br2 and Its Incommensurately Modulated Superstructure Companion2008In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 14, no 11, p. 3434-3441Article in journal (Refereed)
    Abstract [en]

    Compounds containing lone-pair elements such as TeIV are very interesting from the structural point of view, as the lone-pair nonbonding regions create low-dimensional geometrical arrangements. We have synthesized two new compounds with these features—Ba2Cu2Te4O11Br2 (I) and Ba2Cu2Te4O11−δ(OH)2δBr2 (II, δ≈0.57)—as members of the AE-M-Te-O-X (AE=alkaline-earth metal, M=transition metal, X=halide) family of compounds by solid-state reactions. Preliminary single-crystal X-ray analysis indicated that compound I crystallizes in the orthorhombic system, but attempts at refinement proved unsatisfactory. Closer inspection of the reciprocal lattice revealed systematic, non-crystallographic absences that indicate twinning. The structure is in fact triclinic, space group C (equivalent to P), with unit cell parameters (at 120 K) of a=10.9027(9), b=15.0864(7), c=9.379(2) Å, β=106.8947°. It is layered and built from [TeO3E] tetrahedra, [TeO3+1E] trigonal bipyramids (where E is the lone pair of TeIV), [CuO4] squares and irregular [BaO10Br] polyhedra. The crystal structure of II shows the same basic structure as I but contains additional oxygen, probably in the form of OH groups. The presence of satellites reveals that ordering on this O site creates an incommensurate modulation, primarily affecting Br and Te. The modulated structure of II was solved in the triclinic superspace group X(αβγ)0 with the vector q≈1/16 c*.

  • 18.
    Gao, Chuanbo
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Formation mechanism of anionic-surfactant-templated mesoporous silica (AMS)2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This dissertation is focused on synthesis, characterization and formation mechanism of anionic-surfactant-templated mesoporous silica (AMS).

    Structural control mechanisms of AMS are investigated. First, different ionization degree of anionic surfactant affected by the acidity or alkalinity of the synthesis system gives rise to different charging density of micelles and therefore determines the organic/inorganic interface curvature, producing mesophases from cage-type to cylindrical, bicontinuous and lamellar. Second, mesocage/mesocage electrostatic repulsive interaction affects the formation of cage-type mesostructure, which is derived from a full-scaled synthesis-field diagram of AMS. The mesocage/mesocage interaction changes with charge density of mesocages and gives rise to their different packing manners. Third, the structural properties of AMS materials could be tuned by molecular features of surfactant and co-structure-directing agent (CSDA).

    The pore size of AMS is found to be controlled by alkyl chain length, ionization degree of surfactant and the CSDA/surfactant ratio. Alkyl chain length of surfactant determines size of micelles and thus mesopores. Larger ionization degrees of anionic surfactant give rise to smaller pore sizes due to thermodynamic coiling of alkyl chains of surfactant. The hydrophobic interactions between the pendant organic groups of CSDA on the silica wall and the hydrophobic core of the micelles drive a contraction of the mesopores.

    A mesoporous silica with novel bicontinuous cubic Pn-3m structure has been prepared using a diprotic anionic surfactant. 3d-reconstruction of the structure shows that it is bicontinuous composed of an enantiomeric pair of 3d mesoporous networks that are interwoven with each other, divided by a D surface. Inverse replication suggests the possible presence of ordered complimentary micropores in the material.

  • 19.
    Ghalebani, Leila
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Probing Dynamics of Oligosaccharides by Interference Phenomena in NMR Relaxation2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Oligosaccharides (carbohydrates) are a large class of biological molecules that are important as energy sources in the human body and have enormously varied biological functions. It is generally believed that biological activities of carbohydrates are related to their internal dynamics. The dynamic properties of some oligosaccharides in solution are studied in this thesis, by NMR relaxation. We have employed relaxation interference effects to investigate the conformational dynamics within oligosaccharides (in-tramolecular dynamics) and paramagnetic relaxation enhancement (PRE) as an experimental tool to study intermolecular dynamics. Most of the thesis concerns the dynamics of the methylene group in the two possibly mobile parts of the oligosaccharide: in the exocyclic hydroxymethyl moiety and in the glycosidic linkage position. To perform conformational dynamic studies, the more traditional auto-relaxation pa-rameters are combined with the relaxation interference terms or the cross-correlated relaxation rates (CCRRs). Some experimental schemes based on the initial-rate technique were developed for measuring CCRRs. The techniques are useful for labelled sugars as well as naturally abundant ones. Furthermore, various dynamical models ranging from the Lipari–Szabo approach to several more informative and complicated models such as the two-site jump model, restricted internal rotation and slowly relaxing local structure (SRLS), have been employed to interpret our experimental data. We have combined and com-pared different models; we have also developed a novel approach to existing models, by scaling dipolar coupling constants (DCC), to extract the dynamic behaviour and structural properties of the system. We found that the auto- and cross-correlated relaxation data analyses yield a consistent picture of the dynam-ics in all cases. Additionally, our investigations show that CCRRs are practically important for verifica-tion of certain dynamical and structural information that is difficult to be determined by other means. Moreover, the anisotropy of the carbon-13 chemical shielding tensor in the methylene group has been estimated, using the interference between dipole-dipole and chemical shift anisotropy.

    This thesis also discusses using the PRE to investigate sugar dynamics relative to a paramagnetic MRI contrast agent in solution, which might be important in medicine. We have studied the intramolecu-lar dynamics of the trisaccharide raffinose in the presence of a gadolinium complex. We also investigated the effect of translational diffusion instead of rotational diffusion, which is normally more important in NMR. The paramagnetically enhanced spin–lattice relaxation rates of aqueous protons over a wide range of magnetic fields and of carbon-13 and protons of the sugar at high fields have been measured. The nuclear magnetic relaxation dispersion of water protons and the PREs of proton and carbon in the sugar are interpreted in terms of the model recently developed in our laboratory, allowing both outer- and inner-sphere PREs for water protons, but allowing only the outer sphere PRE for nuclei in the sugar. We found that the relative diffusion has a stronger effect on the PRE than the electron spin relaxation.

  • 20.
    Hansson, Helena
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    A Novel Miniaturised Dynamic Hollow-Fibre Liquid-Phase Micro-Extraction Method for Xenobiotics in Human Plasma Samples2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Bioanalytical chemistry is a challenging field, often involving complex samples, such as blood, plasma, serum or urine. In many applications, sample cleanup is the most demanding and time-consuming step.

    In the work underlying this thesis a novel dynamic miniature extractor, known as a hollow-fibre liquid-phase microextractor (HF-LPME), was designed, evaluated and studied closely when used to clean plasma samples. Aqueous-organic-aqueous liquid extraction, in which the organic liquid is immobilised in a porous polypropylene membrane, was the principle upon which the extractor was based, and this is discussed in all the papers associated with this thesis. This type of extraction is known as supported-liquid membrane extraction (SLM). The aim of this work was the development of a dynamic system for SLM. It was essential that the system could handle small sample volumes and had the potential for hyphenations and on-line connections to, for instance, LC/electrospray-MS. The design of a miniaturised HF-LPME device is presented in Paper I. The extraction method was developed for some weakly acidic pesticides and these were also used for evaluation. In the work described in Paper II, the method was optimised on the basis of an experimental design using spiked human plasma samples. Paper III presents a detailed study of the mass-transfer over the liquid membrane. The diffusion through the membrane pores was illustrated by a computer-simulation. Not surprisingly, the more lipophilic, the greater the retention of the compounds, as a result of dispersive forces. The main focus of the work described in Paper IV was to make the HF/LPME system more versatile and user-friendly; therefore, the extractor was automated by hyphenation to a SIA system.

  • 21.
    Hansson, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Colmsjö, Anders
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Study of mass transfer in a dynamic hollow-fibreliquid phase microextraction system2010In: Journal of Separation Science, ISSN 1615-9306, E-ISSN 1615-9314, Vol. 33, no 1, p. 112-119Article in journal (Refereed)
    Abstract [en]

    The extraction characteristics of a dynamic hollow-fibre liquid phase microextractionsystem were investigated by studying the mass transfer and diffusion rates of dinitrophenolsfrom plasma samples over the liquid membrane (dihexylether). The measureddiffusion coefficients were compared with theoretical values calculated from Stokesdiameters. The diffusion mechanism was simulated by computer and the most polarcompounds, 2,4-dinitrophenol and 4,6-o-dinitrocresol, had associated diffusion coefficientsthat were close to the calculated theoretical values. 2-sec-Butyl-4,6 dinitrophenoland 2-tert-butyl-4,6-dinitrophenol, the compounds with the highest log P values, wereretained by the polypropylene membrane, which reduced the experimentally observeddiffusion rates to about half of the theoretical values. The retention was most likely due todispersive forces interacting with the pore inner walls. Extraction was linearly correlatedwith time for all compounds and the repeatability was high (RSDs 7–11%), even for theshortest extraction times. Method LOD as the amount injected ranged between 0.3 and3.1 ng for an extraction cycle of 213 s.

  • 22.
    Hansson, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Karlberg, Bo
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Dynamic hollow-fibre liquid phase microextraction for human plasma samples automated by sequential injection analysisManuscript (preprint) (Other academic)
    Abstract [en]

    This paper presents an easily handled, hollow-fibre liquid phase microextraction (HF-LPME) sample clean-up method, automated by the use of a programmable sequential injection analysis (SIA) system. Use of a SIA system significantly reduces the need for manual sample handling. This new type of clean-up system was assessed and compared with manual HF-LPME for the extraction of acidic compounds (dinitrophenols) from human plasma, in terms of human intervention requirements, efficiency, repeatability and carry-over. Its application to a SIA system for basic compounds (b-blockers) is also presented. The sample aliquots collected off-line from the SIA system were subsequently subjected to separation with LC and the various analytes were detected with ESI-MS.

    Extraction efficiency values between 28 and 56% (RSD 5-10%, n = 7) were achieved for the dinitrophenol compounds after an extraction cycle of 58 min including a 30 min washing step. According to the MS analysis the SIA/HF-LPME method yielded clean chromatograms with no detectable interfering peaks. Ion suppression in positive ESI-MS was between 4 and 21% when tested on extracts with b-blockers.

  • 23.
    Hansson, Helena
    et al.
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Nilsson, Ulrika
    Stockholm University, Faculty of Science, Department of Analytical Chemistry.
    Assessment of a dynamic hollow-fibre liquid phase microextraction system forhuman blood plasma samples2009In: Talanta: The International Journal of Pure and Applied Analytical Chemistry, ISSN 0039-9140, E-ISSN 1873-3573, Vol. 77, no 4, p. 1309-1314Article in journal (Refereed)
    Abstract [en]

    A dynamic liquid phase microextraction (LPME) system, based on hollow-fibre supported liquid membrane(SLM) extraction, was developed for extracting ionisable xenobiotics from human plasma, andits performance was evaluated (in terms of extraction efficiency, reproducibility, durability and carryover)using nitrophenolic compounds as model analytes at concentrations of 0.1–0.5gmL−1 in aqueousstandards. The efficiency and repeatability were tested also on spiked human plasma. The system isnon-expensive, convenient, requires minimal manual handling and enables samples with volumes assmall as 0.2mL to be extracted. For plasma samples extraction efficiencies of between 30 and 58% wereachieved within 20 min, including washing steps. The limit of detection (LOD) values were in the range0.02–0.03gmL−1. The developed system can provide enrichment factors up to eight, based on theinjection-to-acceptor volume ratio (in this case 0.2–0.025 mL). The same hollow-fibre membrane wasused up to 8 days with no loss of efficiency. Carry-over was lower than detection limit.

  • 24.
    Jonsson, Hanna
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Säwén, Elin
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Studies on the conformational flexibility of α-L-Rhap-(1→2)-α-L-Rhap-OMe using molecular simulation and 13C-site-specific labeling: a model for a commonly occurring disaccharide in bacterial polysaccharidesManuscript (preprint) (Other academic)
    Abstract [en]

    Bacterial polysaccharides are comprised of a variety of monosaccharides, L-rhamnose (6-deoxy-Lmannose) being one of them. This sugar is often part of α-(1→2)- and/or α-(1→3)-linkages and wehave therefore studied the disaccharide α-L-Rhap-(1→2)-α-L-Rhap-OMe to obtain information onconformational preferences at this glycosidic linkage. The target disaccharide was synthesized with 13C site-specific labeling at C1' and at C2', i.e., in the terminal group. 2D 1H,13C-HSQC-HECADE and 1H,13C-J-HMBC NMR experiments, 1D 13C and 1H NMR spectra together with total line-shape analysis were used to extract conformationally dependent hetero- and homonuclear spin-spincoupling constants. This resulted in the determination of 2JC2',H1' , 3JC1',C1 , 3JC1',C3 , 3JC2',C2 , 2JC1',C2 ,1JC1',C2' , and 1JC1',H1' . These data together with previously determined JC,H and 1H,1H NOEs result in fourteen conformationally dependent NMR parameters that are available for analysis of glycosidiclinkage flexibility and conformational preferences. A molecular dynamics simulation of the disaccharide with explicit water molecules as solvent showed a major conformational state at ΦH =40° and ψH = –35°, consistent with experimental NMR data.

  • 25.
    Jonsson, Hanna
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    NMR analysis of conformationally dependent nJCH and nJCC in the trisaccharide α-L-Rhap-(1→2)[α-L-Rhap-(1→3)]-α-L-Rhap-OMe and a site-specifically labeled isotopologue thereofManuscript (preprint) (Other academic)
    Abstract [en]

    An array of NMR spectroscopy experiments have been carried out to obtain conformationallydependent 1H,13C- and 13C,13C-spin-spin coupling constants in the trisaccharide a-L-Rhap-(1®2)[a-LRhap-(1®3)]-a-L-Rhap-OMe. The trisaccharide was synthesized with 13C site-specific labeling at C2'and C2'', i.e., in the rhamnosyl groups in order to alleviate 1H spectral overlap. Using both the naturalabundance compound and the 13C-labeled sample 2D 1H,13C-J-HMBC and 1H,13C-HSQC-HECADENMR experiments, total line-shape analysis of 1H NMR spectra and 1D 13C NMR experiments wereemployed to extract 3C,H J , 2C,H J , 3C,C J , and1C,C J . The 13C site-specific labeling facilitates straightforward determination of nC,C J as the splitting of the 13C natural abundance resonances. This studyresulted in seven conformationally dependent coupling constants for the trisaccharide and illustrates theuse of 13C site-specific labeling as a valuable tool that extends the 1D and 2D NMR methods in currentuse to attain both hetero- and homonuclear spin-spin coupling constants.

  • 26.
    Jonsson, K. Hanna M.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Weintraub, Andrej
    Widmalm, Göran
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Structural determination of the O-antigenic polysaccharide from Escherichia coli O742009In: Carbohydrate Research, ISSN 0008-6215, E-ISSN 1873-426X, Vol. 344, no 12, p. 1592-1595Article in journal (Refereed)
    Abstract [en]

    The structure of the O-antigen polysaccharide (PS) from Escherichia coli O74 has been determined. Component analysis, together with 1H and 13C NMR spectroscopy as well as 1H,15N-HSQC experiments were employed to elucidate the structure. Inter-residue correlations were determined by 1H,1H-NOESY and 1H,13C-heteronuclear multiple-bond correlation experiments. The PS is composed of tetrasaccharide repeating units with the following structure:

    Full-size image (5K)

    Cross-peaks of low intensity from an α-linked N-acetylglucosamine residue were present in the NMR spectra, and spectral analysis indicates that they originate from the penultimate residue in the polysaccharide. Consequently, the biological repeating unit has a 3-substituted N-acetyl-d-glucosamine residue at its reducing end. The 1H, 13C and 15N NMR chemical shifts of the α- and β-anomeric forms of d-Fucp3NAc are also reported. The repeating unit of the E. coli O74 O-antigen is identical to that of the capsular polysaccharide from E. coli K45.

  • 27. Kars, Mohammed
    et al.
    Fredrickson, Daniel C.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Gomez-Herrero, A.
    Lidin, Sven
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Inorganic and Structural Chemistry.
    Rebbah, Allaoua
    Otero-Diaz, L. C.
    Structural study by X-ray diffraction and transmission electron microscopy of the misfit compound (SbS1-xSex)(1.16)(Nb1.036S2)(2)2010In: Materials research bulletin, ISSN 0025-5408, E-ISSN 1873-4227, Vol. 45, no 8, p. 982-988Article in journal (Refereed)
    Abstract [en]

    In the Sb-Nb-S-Se system, a new misfit layer compound (MSL) has been synthesized and its structure was determined by combining single crystal X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. It presents a composite crystal structure formed by (SbS1-xSex)slabs stacking alternately with double NbS2 layers and both can be treated as separate monoclinic subsystems. The (SbS1-xSex) slabs comprise a distorted, two-atom-thick layer with NaCl-type structure formed by an array of (SbX5) square pyramids joined by edges (X: S, Se); the NbS2 layers consist of (SbX5) trigonal prisms linked through edge-sharing to form sheets, just as in the 2H-NbS2 structure type. Both sublattices have the same lattice parameters a = 5.7672(19) angstrom, c = 17.618(6) angstrom and beta = 96.18(3)degrees, with incommensurability occurring along the b direction: b(1) = 3.3442(13) angstrom for the NbS2 subsystem and b(2) = 2.8755(13) angstrom for the (SbS1-xSex) subsystem. The occurrence of diffuse scattering intensity streaked along c* indicates that the (SbS1-xSex) subsystem is subjected to extended defects along the stacking direction.

  • 28.
    Kjellberg, Alexandra
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Studies of oligosaccharides and carbon-13 enriched bacterial polysaccharides using NMR spectroscopy and computer simulations1998Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The conformation and dynamics of the trisaccharide methyl β-D-Glcp-(1--> 2)[β-D-Glcp-(1 --> 3)] α-D-Manp and its constituent disaccharides methyl β-D-Glcp-(1 --> 2) α-D-Manp and methyl β-D-Glcp-(1 --> 3) α-D-Manp have been studied using computer simulations and NMR spectroscopy. The computer simulations applied were Metropolis Monte Carlo simulations employing the HSEA force field and Langevin dynamics simulations using the PARM22 and CHEAT95 force fileds. The NMR methods used were measurement of long-range heteronuclear coupling constants across the glycosidic linkages, measurement of carbon-13 nuclear relaxation rates for the determination of dynamical parameters according the Lipari-Szabo "model free" approach and measurements of homonuclear NOE and TROE cross relaxation rates for the determination of proton-proton distances. Experimental data were then compared to the corresponding parameters extracted from the various computer simulations.

    Studies of the carbon-13 labelled O-polysaccharides from Escherichia coli O25 and O91 have also been performed. 13C-13C TOCSY experiments, with the spin-lock on the carbon-13 nuclei, were applied to sugar residues of different geometries. This circumvented the problem of hampered magnetisation transfer encountered in residues with 3JHH < 2Hz when the spin-lock is applied on the protons.The carbon-13 labelling was also used to demonstrate the biosynthesis of one of the substituents in the Escherichia coli O91 O-polysaccharide.

  • 29.
    Klepsch, Mirjam
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    de Gier, Jan-Willem
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Escherichia coli peptide binding protein OppA has a preference for positively chargedpeptidesManuscript (preprint) (Other academic)
  • 30.
    Krogh Andersen, A.M.
    et al.
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Carlson, S.
    High-Pressure Structures of α- and δ-ZrMo2O82001In: Acta Crystallographica Section B Structural science, ISSN 0108-7681, Vol. 57, no 1, p. 20-26Article in journal (Refereed)
    Abstract [en]

    In situ high-pressure synchrotron X-ray powder diffraction studies of trigonal α-ZrMo2O8, zirconium molybdate, have been performed from ambient conditions to 1.9  GPa, over the α–δ phase transition at 1.06–1.11  GPa. The monoclinic structure of δ-ZrMo2O8, stable between 1.1 and 2.5  GPa  at 298  K, has been solved by direct methods and refined using the Rietveld method. Significant distortions of the ZrO6 and MoO4 polyhedral elements are observed for δ-ZrMo2O8, as compared to the ambient conditions of the α-phase, while the packing of anions becomes more symmetric at high pressure.

  • 31.
    Lasselin, Julie
    et al.
    Stockholm University, Faculty of Social Sciences, Stress Research Institute.
    Capuron, Lucile
    Chronic low-grade inflammation in metabolic disorders: relevance for behavioral symptoms.2014In: Neuroimmunomodulation, ISSN 1021-7401, E-ISSN 1423-0216, Vol. 21, no 2-3, p. 95-101Article in journal (Refereed)
    Abstract [en]

    The ability of cytokines to influence cerebral functions and to induce the development of behavioral alterations is well established in conditions of acute or chronic high-grade activation of the innate immune system. Recent evidence suggests that the release of these immune mediators during chronic low-grade endogenous inflammatory processes may also contribute to the development of behavioral alterations. Metabolic disorders, including obesity, type 2 diabetes and the metabolic syndrome, represent examples of those conditions which are both characterized by a chronic low-grade inflammatory state and an increased prevalence of behavioral disorders. In metabolic disorders, the increased production of acute-phase proteins and cytokines (e.g. C-reactive protein, interleukin-6 and tumor necrosis factor-α), but at relatively low levels, may promote and contribute to the development of behavioral symptoms, including depressive symptoms, cognitive impairment, fatigue, sleep problems and pain. This hypothesis is supported by a growing literature referring both to experimental and clinical findings that will be reviewed here.

  • 32.
    Lavén, Gaston
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Palladium(0)-catalyzed benzylation of H-phosphonate diesters: An efficient entry to benzylphosphonates2009In: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, no 2, p. 225-228Article in journal (Refereed)
    Abstract [en]

    A new, efficient method for the synthesis of benzylphosphonate diesters via a palladium(0)-catalyzed cross-coupling reaction between benzyl halides and H-phosphonate diesters, using Pd(OAc)2 as a palladium source and Xantphos as a supporting ligand, has been developed.

  • 33.
    Lavén, Gaston
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Stawinski, Jacek
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthetic Studies on the Preparation of Dinucleoside Phenyl-Phosphonates and Phenyl-Phosphonothioates via Palladium(0) Catalyzed Cross-Coupling2005In: / [ed] Michal Hocek, 2005, p. 195-199Conference paper (Refereed)
    Abstract [en]

    Separate diastereomers of protected dithymidine (3'-5')-phenylphosphonates and dithymidine (3'-5')phenylphosphonothioate were obtained via a palladium(0) catalysed stereo-specific cross-coupling reaction of separate diastereomers of corresponding dinucleoside H-phosphonate and dinucleoside H-phosphonothioate with halobenzenes.

  • 34.
    Leis, J
    et al.
    Tartu Technologies Ltd., 185 Riia Str., 51014 Tartu, Estonia.
    Perkson, A
    Tartu Technologies Ltd., 185 Riia Str., 51014 Tartu, Estonia.
    Arulepp, M
    Tartu Technologies Ltd., 185 Riia Str., 51014 Tartu, Estonia.
    Nigu, P
    Svensson, Gunnar
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Catalytic effects of metals of the iron subgroup on the chlorination of titanium carbide to form nanostructural carbon2002In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 40, no 9, p. 1559-1564Article in journal (Refereed)
    Abstract [en]

    The effect of the reaction temperature and the metals of an iron subgroup on the thermo-chemical treatment of titanium carbide with a chlorine gas and their influence on the carbon structure obtained thereby was studied. Different analytical methods such as porosity measure me tits, X-ray diffraction spectrometry and a high-resolution electron microscopy revealed the catalytic behaviour of the above-mentioned metals. which appeared to support the formation of graphitised carbon at much lower temperatures compared to those needed for the ordinary thermo-chemical chlorination of titanium carbide.

  • 35.
    Liao, Rong-Zhen
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Himo, Fahmi
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Yu, Jian-Guo
    Liu, Ruo-Zhuang
    Theoretical study of the RNA hydrolysis mechanism of the dinuclear zinc enzyme RNase Z2009In: European Journal of Inorganic Chemistry, ISSN 1434-1948, E-ISSN 1099-1948, Vol. 2009, no 20, p. 2967-2972Article in journal (Refereed)
    Abstract [en]

    RNase Z is a dinuclear zinc enzyme that catalyzes the removal of the tRNA 3'-end trailer. Density functional theory is used to investigate the phosphodiester hydrolysis mechanism of this enzyme with a model of the active site constructed on the basis of the crystal structure. The calculations imply that the reaction proceeds through two steps. The first step is a nucleophihc attack by a bridging hydroxide coupled with protonation of the leaving group by a Glu-His diad. Subsequently, a water molecule activated by the same Glu-His diad makes a reverse attack, regenerating the bridging hydroxide. The second step is calculated to be the rate-limiting step with a barrier of 18 kcal/mol, in good agreement with experimental kinetic studies. Both zinc ions participate in substrate binding and orientation, facilitating nucleophilic attack. In addition, they act as electrophilic catalysts to stabilize the pentacoordinate trigonal-bipyramidal transition states.

  • 36.
    Lindberg, Fredrik
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Studies of Oxygen Deficient Complex Cobaltates with Perovskite Related Structures2006Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The present thesis deals with the investigation of some perovskite related complex cobaltates. The phases Sr2Co2-xGaxO5 (0.3 ≤ x ≤ 0.7), Sr2Co2-xAlxO5 (0.3 ≤ x ≤ 0.5), Sr1-xBixCoO3-y (0.1 ≤ x ≤ 0.2), Sr0.75Y0.25Co1-xGaxO2.625 (0.125 ≤ x ≤ 0.375) and Sr0.75Y0.25Co1-xFexO2.625+δ (0.125 ≤ x ≤ 0.625) were synthesised and characterised. All these compounds crystallises with similar structures, they are all composed by altering layers of octahedra and tetrahedra although in the two former, the tetrahedra are organised in chains (the Brownmillerite structure), while in the latter three the tetrahedra arranges as segregated Co4O12 units (the 314 type structure). The techniques X-ray and neutron diffraction, transmission electron microscopy, thermal analysis and magnetic measurements were used to track structural and important physical properties.

  • 37.
    Linderholm, Linda
    et al.
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Athanasiadou, Maria
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Jakobsson, Kristina
    Lunds universitet.
    Bergman, Åke
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Environmental Chemistry.
    Persistent organic pollutants in children working and living at urban waste disposal sites in Nicaragua and Bangladesh2010Conference paper (Other academic)
  • 38.
    Lopez-Ortega, Alberto
    et al.
    Campus Universitat Autnoma de Barcelona.
    Tobia, Dina
    CNEA-CONICET.
    Winkler, Elin
    CNEA-CONICET.
    Golosovsky, Igor V.
    S:t Petersburg University.
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Estrade, Sonia
    Universitat de Barcelona.
    Estrader, Marta
    Universitat de Barcelona.
    Sort, Jordi
    Universitat Autnoma de Barcelona..
    Gonzalez, Angel
    Institut Laue Langevin.
    Surinach, Santiago
    Universitat Autnoma de Barcelona.
    Arbiol, Jordi
    Universitat Autnoma de Barcelona.
    Peiro, Francesca
    Universitat de Barcelona.
    Zysler, Roberto D.
    CNEA-CONICET.
    Dolors Baro, Maria
    Universitat Autnoma de Barcelona.
    Nogues, Josep
    Universitat Autnoma de Barcelona.
    Size-Dependent Passivation Shell and Magnetic Properties in Antiferromagnetic/Ferrimagnetic Core/Shell MnO Nanoparticles2010In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 132, no 27, p. 9398-9407Article in journal (Refereed)
    Abstract [en]

    The magnetic properties of bimagnetic core/shell nanoparticles consisting of an antiferromagnetic MnO core and a ferrimagnetic passivation shell have been investigated. It is found that the phase of the passivation shell (gamma-Mn2O3 or Mn3O4) depends on the size of the nanoparticles. Structural and magnetic characterizations concur that while the smallest nanoparticles have a predominantly gamma-Mn2O3 shell, larger ones have increasing amounts of Mn3O4. A considerable enhancement of the Neel temperature, T-N, and the magnetic anisotropy of the MnO core for decreasing core sizes has been observed. The size reduction also leads to other phenomena such as persistent magnetic moment in MnO up to high temperatures and an unusual temperature behavior of the magnetic domains.

  • 39.
    Lund, Kristina
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    Structural and Morphological Studies of Mesoporous Crystals2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Mesoporous silica and carbon have been synthesised and characterised by X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM) and nitrogen adsorption. Surface structure, size and shape (morphology) of particles have been of special interest in this work. These parameters are of importance in understanding the growth mechanism and structural characteristics of mesoporous materials overall, which has been the main aim of this thesis.

    The novel synthetic system involving preparation of AMS (anionic surfactant-templated silica) crystals, where the non-toxic N-acyl-amino acids are used as surfactant together with a co-structure directing agent, was investigated in two different surfactant systems.

    Particle size and shape of AMS solids were controlled through the addition of a polymeric dispersant, which slowed down the system dynamics. However, the response for the two synthetic systems investigated, proved to be different. Nanoparticles of cage-type cubic Fd-3m crystals were obtained in one system, whereas facetted particles formed in a near-to-equilibrium growth in the bicontinuous cubic Ia-3d case.

    The surface fine structure of mesoporous silica was observed by high resolution SEM, leading to an understanding of the pore accessibility at the particle surface of SBA-15 silica. Furthermore, discrepancies in the XRD patterns of mesoporous tube-type carbon CMK-5 with different pore diameters were observed. XRD patterns displaying accidental extinction of the 10 reflection were observed in CMK-5 samples prepared with the widest pore diameter. An analytical approach was formulated in order to simulate the variation of XRD intensity for carbon crystals with p6mm symmetry. TEM observations of inner and outer diameter of the carbon tubes were used to interpret the diminishing of certain reflections and we observed good agreement between experimental observations and our calculations.

  • 40.
    Merritt, Eleanor A.
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Malmgren, Joel
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Klinke, Felix J.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Olofsson, Berit
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Synthesis of diaryliodonium triflates using environmentally benign oxidizing agents2009In: Synlett: Accounts and Rapid Communications in Synthetic Organic Chemistry, ISSN 0936-5214, E-ISSN 1437-2096, no 14, p. 2277-2280Article in journal (Refereed)
  • 41.
    Miyasaka, Keiichi
    Stockholm University, Faculty of Science, Department of Physical, Inorganic and Structural Chemistry.
    A structural study into the boundary surface and associated curvature of three-dimensional mesoporous silica crystals2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Since their first discovery in the early 1990s, mesoporous crystals (MCs) have fascinated researchers in various fields because of their interesting structures and their potential uses. Electron crystallography (EC) gives the direct three-dimensional (3D) realization of a crystal as a reconstructed electrostatic potential map (EPM). Various 3D-EPMs of silica MCs with cubic symmetry have been previously obtained by EC.

    The main task in this thesis is the development of structural analyses focusing on MCs and thus to evaluate the properties of periodic mesopores within EC data. How MC structures can be described and solved by EC is discussed in terms of the interpretation of the reconstructed 3D-EPM. Assuming a regime of an equi-potential surface (EPS), a structural description for MCs is suggested as a surface that optimizes the curvature elasticity evaluated on every EPS. The geometric properties of cubic MCs so far already reconstructed by EC, are then analyzed on the basis of the optimized EPSs. The analysis provides the property of the mesopores independently from gas adsorption measurements. A large cage-like MC is further studied by in-situ synchrotron powder X-ray diffraction to help understand the nitrogen adsorption process onto the mesopore wall.

    As an additional study, a silica MC showing its crystal morphologies of icosahedron, decahedron, etc. is studied. Results by EC suggest that the spherical uni-modal cages form the cubic close packing. The morphologies observed are explained in terms of the multiple twinning, which is analogous to metal nanoparticles. The occurrence of multiple twinning in MCs is discussed in light of the synthesis condition and the shape of micelles.

  • 42.
    Moreira Bastos, Patricia
    Stockholm University, Faculty of Science, Department of Environmental Chemistry.
    Comparison of experimentally and theoretically determined oxidation and photochemical transformation rates of some organohalogens to promote prediction of persistence2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The diversity of choices we have to make everyday influence our environment and ourselves in more ways than most of us realise. Anthropogenic substances, such as flame retardants, date back as early as 450 BC when the Egyptians used alum to reduce flammability. The increasing demand for new articles has led to an increased production of chemical substances, for which many are commercially produced without complete knowledge on properties such as persistence, bioaccumulation and toxicology (PBT). Commercial compounds may be properly tested and denominated as “safe” regarding PBT properties, but their degradation products and/or metabolites may cause environmental impact.

    The availability of uniform and accurate data for prediction of persistence is of key importance for the understanding of chemical fate. A method to determine the susceptibility of chemicals to undergo oxidation in water has been developed and applied on several organohalogens, including PBDEs and OH-PBDEs. The method was used to determine reaction rates and the group of OH-PBDEs were subsequently subjected to photolysis by use of UV-light. Hence, susceptibility to undergo both oxidation and photolysis for the OH-PBDEs were investigated and compared to previously reported degradation rates on PBDEs.

    As a final step in promoting the prediction of persistence, Quantitative structure-property relationship (QSPR) models were performed on a set of compounds which had undergone photolytic degradation under similar conditions. The QSPRs were used as a preliminary step in predicting photolysis half-lives for chemical substances and to determine which physicochemical descriptors are of greatest importance thereof.

    This thesis presents the possibility of performing and assessing oxidation transformations on compounds of low and high water solubility, photolysis transformations in various media and using obtained data to predict behaviour via QSPR models, to promote predictions of persistence.

  • 43.
    Oglęcka, Kamila
    et al.
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Lundberg, Pontus
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Magzoub, Mazin
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Eriksson, L. E. Göran
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Langel, Ülo
    Stockholm University, Faculty of Science, Department of Neurochemistry.
    Gräslund, Astrid
    Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
    Relevance of the N-terminal NLS-like sequence for membrane interactions of the Prion protein2007In: Biochimica et Biophysica Acta. MR. Reviews on Biomembranes, ISSN 0304-4157, E-ISSN 1879-257X, Vol. 1778, no 1, p. 206-213Article in journal (Refereed)
    Abstract [en]

    We investigated the nuclear localization-like sequence KKRPKP, corresponding to the residues 23–28 in the mouse prion protein (mPrP), for its membrane perturbation activity, by comparing effects of two mPrP-derived peptides, corresponding to residues 1–28 (mPrPp(1–28)) and 23–50 (mPrPp(23–50)), respectively. In erythrocytes, mPrPp(1–28) induced 60% haemoglobin leakage after 30 min, whereas mPrPp(23–50) had negligible effects. In calcein-entrapping, large unilamellar vesicles (LUVs), similar results were obtained. Cytotoxicity estimated by lactate dehydrogenase leakage from HeLa cells, was found to be 12% for 50 μM mPrPp(1–28), and 1% for 50 μM mPrPp(23–50). Circular dichroism spectra showed structure induction of mPrPp(1–28) in the presence of POPC:POPG (4:1) and POPC LUVs, while mPrPp(23–50) remained a random coil. Membrane translocation studies on live HeLa cells showed mPrPp(1–28) co-localizing with dextran, suggesting fluid-phase endocytosis, whereas mPrPp(23–50) hardly translocated at all. We conclude that the KKRPKP-sequence is not sufficient to cause membrane perturbation or translocation but needs a hydrophobic counterpart.

  • 44.
    Olsson, R T
    et al.
    KTH.
    Azizi Samir, M A S
    Nanocomposites and Bioconcepts s.a.r.l., N170 Tanalt Alhouda (Agadir), .
    Salazar-Alvarez, German
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Belova, L
    KTH.
    Ström, V
    KTH.
    Berglund, L A
    KTH.
    Ikkala, O
    Helsinki University of Technology/Aalto University School of Science and Technology, Molecular Materials, Department of Applied Physics.
    Nogués, J
    Universitat Autònoma de Barcelona.
    Gedde, U W
    KTH.
    Making flexible magnetic aerogels and stiff magnetic nanopaper using cellulose nanofibrils as templates2010In: Nature Nanotechnology, ISSN 1748-3387, E-ISSN 1748-3395, Vol. 5, p. 584-588Article in journal (Refereed)
    Abstract [en]

    Nanostructured biological materials inspire the creation of materials with tunable mechanical properties. Strong cellulose nanofibrils derived from bacteria or wood can form ductile or tough networks that are suitable as functional materials. Here, we show that freeze-dried bacterial cellulose nanofibril aerogels can be used as templates for making lightweight porous magnetic aerogels, which can be compacted into a stiff magnetic nanopaper. The 20-70-nm-thick cellulose nanofibrils act as templates for the non-agglomerated growth of ferromagnetic cobalt ferrite nanoparticles (diameter, 40-120 nm). Unlike solvent-swollen gels and ferrogels, our magnetic aerogel is dry, lightweight, porous (98%), flexible, and can be actuated by a small household magnet. Moreover, it can absorb water and release it upon compression. Owing to their flexibility, high porosity and surface area, these aerogels are expected to be useful in microfluidics devices and as electronic actuators.

  • 45.
    Olsson, Vilhelm
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Functionalization of Unactivated Alkenes trough Iridium-Catalyzed Borylation of Carbon-Hydrogen Bonds. Mechanism and Synthetic ApplicationsManuscript (Other academic)
  • 46.
    Olsson, Vilhelm
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Sebelius, Sara
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Selander, Nicklas
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Szabó, Kálmán
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Direct Boronation of Allyl Alcohols with Diboronic Acid Using Palladium Pincer-Complex Catalysis. A Remarkably Facile Allylic Displacement of the Hydroxy Group under Mild Reaction Conditions2006In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 128, no 14, p. 4588-4589Article in journal (Refereed)
    Abstract [en]

    Allyl alcohols were converted to allyl boronic acids and subsequently to trifluoro(allyl)borates with tetrahydroxy diboron using palladium pincer-complex catalysis. These reactions are regio- and stereoselective proceeding with high isolated yields. Competitive boronation experiments indicate that under the applied reaction conditions the allylic displacement of a hydroxy group is faster than the displacement of an acetate leaving group. It is assumed that the hydroxy group of the allyl alcohol is converted to a diboronic acid ester functionality, which can easily be substituted.

  • 47.
    Privalov, Timofei
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Boschloo, Gerrit
    Hagfeldt, Anders
    Svensson, Per H.
    Kloo, Lars
    A study of the interactions between I-/I3- redox , mediators amd organometallic sensitizing dyes in solar cells2009In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 113, no 2, p. 783-790Article in journal (Refereed)
  • 48.
    Samec, Joseph S M
    et al.
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Mony, Laetitia
    Bäckvall, Jan-E
    Efficient Ruthenium-Catalyzed Transfer Hydrogenation of Functionalized Imines by Isopropanol under Controlled Microwave Heating2005In: Canadian journal of chemistry (Print), ISSN 0008-4042, E-ISSN 1480-3291, Vol. 83, no 6, p. 909-916Article in journal (Refereed)
    Abstract [en]

    Transfer hydrogenation of various functionalized imines by isopropanol catalyzed by [Ru(CO)(2)(Ph4C4CO)](2) (3) has been studied. The use of either an oil bath or controlled microwave heating in toluene led to an efficient procedure with high turnover frequencies and the product amines were obtained in high yields. An advantage with catalyst 3 over the conventional [Ru-2(CO)(4)(mu-H)(Ph4C4COHOCC4Ph4)] (1) is the absence of an initiation period, which results in a faster reaction with 3 as compared to 1.

  • 49. Sjödin, Martin
    et al.
    Styring, Stenbjörn
    Wolpher, Henriette
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    Xu, Yunhua
    Sun, Licheng
    Hammarström, Leif
    Switching the redox mechanism: Models for proton coupled electron transfer from tyrosine and tryptophan2005In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 127, no 11, p. 3855-3863Article in journal (Refereed)
    Abstract [en]

    The coupling of electron and proton transfer is an important controlling factor in radical proteins, such as photosystem II, ribinucleotide reductase, cytochrome oxidases, and DNA photolyase. This was investigated in model complexes in which a tyrosine or tryptophan residue was oxidized by a laser-flash generated trisbipyridine-Ru-III moiety in an intramolecular, proton-coupled electron transfer (PCET) reaction. The PCET was found to proceed in a competition between a stepwise reaction, in which electron transfer is followed by deprotonation of the amino acid radical (ETPT), and a concerted reaction, in which both the electron and proton are transferred in a single reaction step (CEP). Moreover, we found that we could analyze the kinetic data for PCET by Marcus' theory for electron transfer. By altering the solution pH, the strength of the Ru-III oxidant, or the identity of the amino acid, we could induce a switch between the two mechanisms and obtain quantitative data for the parameters that control which one will dominate. The characteristic pH-dependence of the CEP rate (M. Sjodin et al. J. Am. Chem. Soc. 2000, 122, 3932) reflects the pH-dependence of the driving force caused by proton release to the bulk. For the pH-independent ETPT on the other hand, the driving force of the rate-determining ET step is pH-independent and smaller. On the other hand, temperature-dependent data showed that the reorganization energy was higher for CEP, while the pre-exponential factors showed no significant difference between the mechanisms. Thus, the opposing effect of the differences in driving force and reorganization energy determines which of the mechanisms will dominate. Our results show that a concerted mechanism is in general quite likely and provides a low-barrier reaction pathway for weakly exoergonic reactions. In addition, the kinetic isotope effect was much higher for CEP (k(H)/k(D) &GT; 10) than for ETPT (k(H)/k(D) = 2), consistent with significant changes along the proton reaction coordinate in the rate-determining step of CEP.

  • 50.
    Stenutz, Roland
    Stockholm University, Faculty of Science, Department of Organic Chemistry.
    The structure and conformation of saccharides determined by experiment and simulation1997Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A computer program, CASPER, for sequence determination of oligosaccharides and regular polysaccharides using NMR-data, has been extended to support multiply branched structures. The program has been modified to allow the use of incomplete experimental data since spectral overlap can be a problem even at high fields. The resulting program was tested and used in the structure determination of the capsular polysaccharide from Klebsiella type K52.

    Four carboxyethyl-substituted sugars, methyl 4-O-[(R)- and (S)-1-carboxyethyl]-a-L-rhamnopyranoside and methyl 6-O-[(R)- and (S)-1-carboxyethyl]-a-D-galactopyranoside have been synthesized. The conformational properties of the latter two have been investigated by both NMR spectroscopy and molecular modelling studies. For the NMR-studies stereospecifically deuterated compounds were prepared.

12 1 - 50 of 58
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