Now showing items 37-56 of 247

    • Caesium Fluoride-Mediated Hydrocarboxylation of Alkenes and Allenes: Scope and Mechanistic Insights 

      Gevorgyan, Ashot; Obst, Marc; Guttormsen, Yngve; Maseras, Feliu; Hopmann, Kathrin Helen; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-09-11)
      A caesium fluoride-mediated hydrocarboxylation of olefins is disclosed that does not rely on precious transition metal catalysts and ligands. The reaction occurs at atmospheric pressures of CO<sub>2</sub> in the presence of 9-BBN as a stoichiometric reductant. Stilbenes, β-substituted styrenes and allenes could be carboxylated in good yields. The developed methodology can be used for preparation of ...
    • Caffeine supplementation does not affect match activities and fatigue resistance during match play in young football players 

      Pettersen, Svein Arne; Krustrup, Peter; Bendiksen, Mads; Randers, Morten B.; Brito, Joao; Bangsbo, Jens; Yun, Jin; Mohr, Magni (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-10-30)
      The study examined the effect of caffeine supplementation on match activities and development of fatigue during a football match. In a randomised, double-blind cross-over design, two experimental football games separated by 7 days were organised between the junior teams of two professional football clubs (17.6 ± 1.1 years (±s), 71.7 ± 6.9 kg, 13.9% ± 5.0% body fat). The players ingested either a ...
    • Calculations of the EPR g-tensor using unrestricted two- and four-component relativistic approaches within the HF and DFT frameworks 

      Cherry, Peter J.; Komorovsky, Stanislav; Malkin, Vladimir G.; Malkina, Olga L. (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-06-08)
      Approaches and programs for calculations of the EPR g-tensor in the framework of the two- and four-component methods are still very rare. There are three main reasons for this: the wider community's unawareness of the importance of second- and higher order spin–orbit effects on the g-tensor, the methodological problems associated with performing such calculations and the lack of understanding of ...
    • Carbon-carbon bonds with CO2: Insights from computational studies 

      Obst, Marc Ferry; Pavlovic, Ljiljana; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-02-17)
      In this mini-review, we provide an overview of recent computational studies on homogeneous transition metal-catalyzed carbon-carbon bond formation with CO2. We cover substitution and addition reactions involving different metals (mainly Ni, Rh, Cu) and substrates (alkanes, alkenes, alkynes, arenes) with focus on the mechanistic details. The CO2 insertion step is generally found to be rate-limiting. ...
    • Catalytic Intermolecular Functionalization of Benzimidazoles 

      Hansen, Jørn H; Fjellaksel, Richard (Peer reviewed; Chapter; Bokkapittel, 2019-06-25)
      This chapter describes contemporary strategies for selective catalytic intermolecular functionalization of the benzimidazole scaffold. Functionalization at nitrogen and position C-2 is well developed employing copper, palladium, rhodium, nickel, and cobalt catalysis. Direct CH activation is the predominant approach to C-2 functionalization. Nickel-based catalysts can activate C—O bonds in conjunction ...
    • Channel interference in multiphoton absorption 

      Alam, MD Mehboob; Beerepoot, Maarten; Ruud, Kenneth (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-06-30)
      We extend the theory of channel interference to higher-order multiphoton absorption processes. We derive an explicit expression for channel interference in a three-photon absorption process and propose a general scheme for deriving such expressions for multiphoton absorption processes of any order. Based on this general scheme, we derive and analyze the simplest few-state models for multiphoton ...
    • Characterization of a cold-active and salt tolerant esterase identified by functional screening of Arctic metagenomic libraries 

      De Santi, Concetta; Altermark, Bjørn; Pierechod, Marcin Miroslaw; Ambrosino, Luca; de Pascale, Donatella; Willassen, Nils Peder (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-01-19)
      Background: The use of metagenomics in enzyme discovery constitutes a powerful approach to access to genomes of unculturable community of microorganisms and isolate novel valuable biocatalysts for use in a wide range of biotechnological and pharmaceutical fields. Results: Here we present a novel esterase gene (lip3) identified by functional screening of three fosmid metagenomic libraries, ...
    • Characterization of an intertidal zone metagenome oligoribonuclease and the role of the intermolecular disulfide bond for homodimer formation and nuclease activity 

      Piotrowski, Yvonne; Berg, Kristel; Klebl, David Paul; Leiros, Ingar; Larsen, Atle Noralf (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-17)
      The gene encoding MG Orn has been identified from a metagenomic library created from the intertidal zone in Svalbard and encodes a protein of 184 amino acid residues. The <i>mg orn</i> gene has been cloned, recombinantly expressed in <i>Escherichia coli</i>, and purified to homogeneity. Biochemical characterization of the enzyme showed that it efficiently degrades short RNA oligonucleotide substrates ...
    • Chemo-inspired Genetic Algorithm for Optimizing the Piecewise Aggregate Approximation 

      Muhammad Fuad, Muhammad Marwan (Journal article; Tidsskriftartikkel; Peer reviewed, 2015)
      In a previous work we presented DEWPAA: an improved version of the piecewise aggregate approximation representation method of time series. DEWPAA uses differential evolution to set weights to different segments of the time series according to their information content. In this paper we use a hybrid of bacterial foraging and genetic algorithm (CGA) to set the weights of the different segments in our ...
    • Chemometric analysis for pollution source assessment of harbour sediments in Arctic locations 

      Pedersen, Kristine Bondo; Lejon, Tore; Jensen, Pernille E.; Ottosen, Lisbeth M. (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-04-16)
      Pollution levels, pollutant distribution and potential source assessments based on multivariate analysis (chemometrics) were made for harbour sediments from two Arctic locations; Hammerfest in Norway and Sisimiut in Greenland. High levels of heavy metals were detected in addition to organic pollutants. Preliminary assessments based on Principal Component Analysis (PCA) revealed different sources and ...
    • Closely-related Photobacterium strains comprise the majority of bacteria in the gut of migrating Atlantic cod (Gadus morhua) 

      Le Doujet, Typhaine; De Santi, Concetta; Klemetsen, Terje; Hjerde, Erik; Willassen, Nils Peder; Haugen, Peik (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-04-17)
      <p><i>Background - </i>The population of Atlantic cod (<i>Gadus morhua</i>), also known as Northeast Arctic cod, migrating Atlantic cod, or simply “skrei,” lives mainly in the Barents Sea and Svalbard waters and migrates in annual cycles to the Norwegian coast in order to spawn eggs during late winter. It is the world’s largest population of Atlantic cod, and the population is distinct from the ...
    • Co-cultivation and transcriptome sequencing of two co-existing fish pathogens Moritella viscosa and Aliivibrio wodanis 

      Hjerde, Erik; Karlsen, Christian; Sørum, Henning; Parkhill, Julian; Willassen, Nils Peder; Thomson, Nicholas R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-06-10)
      Background: Aliivibrio wodanis and Moritella viscosa have often been isolated concurrently from fish with winterulcer disease. Little is known about the interaction between the two bacterial species and how the presence of one bacterial species affects the behaviour of the other. Results: The impact on bacterial growth in co-culture was investigated in vitro, and the presence of A. wodanis has an ...
    • Cobalt-Catalysed Alkene Hydrogenation: A Metallacycle Can Explain the Hydroxyl Activating Effect and the Diastereoselectivity 

      Morello, Glenn Robert; Zhong, Hongyu; Chirik, Paul J.; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-04)
      Bis(phosphine)cobalt dialkyl complexes have been reported to be highly active in the hydrogenation of tri-substituted alkenes bearing hydroxyl substituents. Alkene substrates containing ether, ester, or ketone substituents show minimal reactivity, indicating an activating effect of the hydroxyl group. The mechanistic details of bis(phosphine)cobalt-catalysed hydrogenation were recently evaluated ...
    • Cold shock induction of recombinant Arctic environmental genes 

      Bjerga, Gro Elin Kjæreng; Williamson, Adele Kim (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-08-19)
      Background: Heterologous expression of psychrophilic enzymes in E. coli is particularly challenging due to their intrinsic instability. The low stability is regarded as a consequence of adaptation that allow them to function at low temperatures. Recombinant production presents a significant barrier to their exploitation for commercial applications in industry. <p>Methods: As part of an enzyme ...
    • A combined quantum mechanics/molecular mechanics study of the one- and two-photon absorption in the green fluorescent protein 

      Steindal, Arnfinn Hykkerud; Olsen, Jógvan Magnus Haugaard; Ruud, Kenneth; Frediani, Luca; Kongsted, Jacob (Journal article; Tidsskriftartikkel; Peer reviewed, 2012-02-01)
      We present for the first time a QM/MM study of the one- and two-photon absorption spectra of the GFP chromophore embedded in the full protein environment described by an advanced quantum mechanically derived polarizable force field. The calculations are performed on a crystal structure of the green fluorescent protein (GFP) using the polarizable embedding density functional theory (PE-DFT) scheme. ...
    • Communication: The absolute shielding scales of oxygen and sulfur revisited 

      Komorovsky, Stanislav; Repisky, Michal; Malkin, Elena; Ruud, Kenneth; Gauss, Jürgen (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-03-04)
      We present an updated semi-experimental absolute shielding scale for the 17O and 33S nuclei. These new shielding scales are based on accurate rotational microwave data for the spin–rotation constants of H2 17O [Puzzarini et al., J. Chem. Phys. 131, 234304 (2009)], C17O [Cazzoli et al., Phys. Chem. Chem. Phys. 4, 3575 (2002)], and H2 33S [Helgaker et al., J. Chem. Phys. 139, 244308 (2013)] ...
    • Comparative conformational analyses and molecular dynamics studies of glycylglycine methyl ester and glycylglycine N -methylamide 

      Thakkar, Balmukund S.; Engh, Richard Alan (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-01-24)
      Compared to their amide analogs, peptidic esters have a lower propensity for intramolecular hydrogen bonding, and thus most likely quite different stable geometries. On the other hand, their similarity and facile conversion to peptides has led to their broad use in synthetic and biological applications. This dichotomy creates a need to understand their conformational properties. Here, we study the ...
    • A comparative study of cold-and warmadapted Endonucleases A using sequence analyses and molecular Dynamics simulations 

      Michetti, Davide; Brandsdal, Bjørn Olav; Bon, Davide; Isaksen, Geir Villy; Tiberti, Matteo; Papaleo, Elena (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-02-13)
      The psychrophilic and mesophilic endonucleases A (EndA) from Aliivibrio salmonicida (VsEndA) and Vibrio cholera (VcEndA) have been studied experimentally in terms of the biophysical properties related to thermal adaptation. The analyses of their static X-ray structures was no sufficient to rationalize the determinants of their adaptive traits at the molecular level. Thus, we used Molecular Dynamics ...
    • A comparative theoretical study on core-hole excitation spectra of azafullerene and its derivatives 

      Deng, Yunfeng; Gao, Bin; Deng, Mingsen; Luo, Yi (Journal article; Tidsskriftartikkel; Peer reviewed, 2014)
    • Comparison of 2-compartment, 3-compartment and stack designs for electrodialytic removal of heavy metals from harbour sediments 

      Pedersen, Kristine Bondo; Ottosen, Lisbeth M.; Jensen, Pernille E.; Lejon, Tore (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-01)
      Comparisons of cell and stack designs for the electrodialytic removal of heavy metals from two harbour sediments, were made. Multivariate modelling showed that sediment properties and experimental set-ups had the highest influence on the heavy metal removal indicating that they should be modelled and analysed separately. Clean-up levels of Cu, Pb and Zn were significantly higher for the cell designs, ...