Now showing items 31-50 of 247

    • Benchmarking the Performance of Exchange-Correlation Functionals for Predicting Two-Photon Absorption Strengths 

      Beerepoot, Maarten; Alam, MD Mehboob; Bednarska, Joanna; Bartkowiak, Wojciech; Ruud, Kenneth; Zaleśny, Robert (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-31)
      The present work investigates the performance of exchange–correlation functionals in the prediction of two-photon absorption (2PA) strengths. For this purpose, we considered six common functionals used for studying 2PA processes and tested these on six organoboron chelates. The set consisted of two semilocal (PBE and BLYP), two hybrid (B3LYP and PBE0), and two range-separated (LC-BLYP and CAM-B3LYP) ...
    • Benchmarking two-photon absorption cross sections: performance of CC2 and CAM-B3LYP 

      Beerepoot, Maarten T. P.; Friese, Daniel Henrik; List, Nanna Holmgaard; Kongsted, Jacob; Ruud, Kenneth (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-06-25)
      We investigate the performance of CC2 and TDDFT/CAM-B3LYP for the calculation of two-photon absorption (TPA) strengths and cross sections and contrast our results to a recent coupled cluster equation-of-motion (EOM-EE-CCSD) benchmark study [K. D. Nanda and A. I. Krylov, J. Chem. Phys., 2015, 142, 064118]. In particular, we investigate whether CC2 TPA strengths are significantly overestimated compared ...
    • Biochemical characterization of a family 15 carbohydrate esterase from a bacterial marine Arctic metagenome 

      De Santi, Concetta; Willassen, Nils Peder; Williamson, Adele Kim (Journal article; Tidsskriftartikkel; Peer reviewed, 2016)
      Background The glucuronoyl esterase enzymes of wood-degrading fungi (Carbohydrate Esterase family 15; CE15) form part of the hemicellulolytic and cellulolytic enzyme systems that break down plant biomass, and have possible applications in biotechnology. Homologous enzymes are predicted in the genomes of several bacteria, however these have been much less studied than their fungal counterparts. ...
    • Biochemical characterization of ParI, an orphan C5-DNA methyltransferase from Psychrobacter arcticus 273-4 

      Grgic, Miriam; Williamson, Adele Kim; Bjerga, Gro Elin Kjæreng; Altermark, Bjørn; Leiros, Ingar (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-05-25)
      <p>Cytosine-specific DNA methyltransferases are important enzymes in most living organisms. In prokaryotes, most DNA methyltransferases are members of the type II restriction-modification system where they methylate host DNA, thereby protecting it from digestion by the accompanying restriction endonucleases. DNA methyltransferases can also act as solitary enzymes having important roles in controlling ...
    • Bioprospecting around Arctic islands: Marine bacteria as rich source of biocatalysts 

      De Santi, Concetta; Altermark, Bjørn; de Pascale, Donatella; Willassen, Nils Peder (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-11)
      We have investigated the biotechnological potential of Arctic marine bacteria for their ability to produce a broad spectrum of cold-active enzymes. Marine bacteria exhibiting these features are of great interest for both fundamental research and industrial applications. Macrobiota water and sediment samples have been collected during 2010 and 2011expeditions around the Lofoten and Svalbard islands. ...
    • The Blue–Violet Color of Pentamethylbismuth: A Visible Spin-Orbit Effect 

      Conradie, Jeanet; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-12-22)
      Two-component relativistic time-dependent density functional theory calculations with spin-orbit coupling predict yellow and orange–red absorption for BiPh5 and BiMe5, respectively, providing an excellent explanation for their respective violet and blue–violet colors. According to the calculations, the visible absorption is clearly attributable to a single transition from a ligand-based HOMO ...
    • 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 ...