Viser treff 487-506 av 527

    • Tailored Leaching Tests as a Tool for Environmental Management of Mine Tailings Disposal at Sea 

      Pedersen, Kristine B.; Lejon, Tore; Evenset, Anita (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-03-10)
      The expanding human activities in coastal areas increase the need for developing solutions to limit impacts on the marine environment. Sea disposal affects the marine environment, but despite the growing knowledge of potential impacts, there are still no standardized leaching tests for sea disposal. The aim of this study was to contribute to the development of leaching tests, exemplified using ...
    • Temperature adaptation of DNA ligases from psychrophilic organisms 

      Berg, Kristel; Leiros, Ingar; Williamson, Adele Kim (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-02)
      DNA ligases operating at low temperatures have potential advantages for use in biotechnological applications. For this reason, we have characterized the temperature optima and thermal stabilities of three minimal Lig E-type ATP-dependent DNA ligase originating from Gram-negative obligate psychrophilic bacteria. The three ligases, denoted Vib-Lig, Psy-Lig, and Par-Lig, show a remarkable range of ...
    • Temporal dynamics of intra-and extra-cellular microcystins concentrations in Koka reservoir (Ethiopia): Implications for public health risk 

      Tilahun, Samson; Kifle, Demeke; Zewde, Tigist W; Johansen, Jostein a; Demissie, Taye Beyene; Hansen, Jørn H (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-06-20)
      This study was carried out with a view of understanding the temporal dynamics of microcystin concentrations in both algal seston and water samples and the associated public health risk. All the major MC variants, namely MC-LR, MC-YR, and MC-RR, were detected in both the algal seston and water samples. In the majority of the samples, the most potent variant, MC-LR, constituted the greatest proportion ...
    • Theoretical Analysis of NMR Shieldings in XSe and XTe (X= Si, Ge, Sn and Pb): The Spin–Rotation Constant Saga 

      Demissie, Taye Beyene (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-12-21)
      The nuclear spin-rotation (NSR) and absolute nuclear magnetic resonance (NMR) shielding tensors of the nuclei in the series of X<sup>77</sup>Se and X<sup>125</sup>Te (X = <sup>29</sup>Si, <sup>73</sup>Ge, <sup>119</sup>Sn and <sup>207</sup>Pb) are calculated using fourcomponent relativistic density functional theory (DFT) and coupled-cluster singles-doubles with a perturbative triples correction ...
    • Theoretical Photoelectron Spectroscopy of Low-Valent Carbon Species: A ∼6 eV Range of Ionization Potentials among Carbenes, Ylides, and Carbodiphosphoranes 

      Ghosh, Abhik; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-12-02)
      High-quality density functional theory calculations underscore a nearly 6 eV range for the ionization potentials (IPs) of neutral, low-valent carbon compounds, including carbenes, ylides, and zero-valent carbon compounds (carbones) such as carbodiphosphoranes (CDPs) and carbodicarbenes. Thus, adiabatic IPs as low as 5.5 ± 0.1 eV are predicted for CDPs, which are about 0.7–1.2 eV lower than those of ...
    • A Theoretical Search for Stable Terminal Carbides 

      Ghosh, Abhik; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-11-20)
      xploratory scalar-relativistic density functional theory (B3LYP*-D3/ZORA-STO-TZ2P) calculations have been used to examine the stability and bonding of pseudotetrahedral Group 8 (Fe, Ru, and Os) and Group 9 (Co, Rh, and Ir) terminal carbide complexes with dδ4 ground states and tripodal tris(N-heterocyclic-carbene) supporting ligands. The calculations predict relatively low adiabatic ionization ...
    • A thermally stable {FeNO}(8) complex: properties and biological reactivity of reduced MNO systems 

      Patra, Ashis K.; Dube, Koustubh S.; Sanders, Brian C.; Papaefthymiou, Georgia C.; Conradie, Jeanet; Ghosh, Abhik; Harrop, Todd C. (Journal article; Tidsskriftartikkel; Peer reviewed, 2012-10-06)
      Reduced nitrogen oxide ligands such as NO<sup>−</sup>/HNO or nitroxyl participate in chemistry distinct from nitric oxide (NO). Nitroxyl has been proposed to form at heme centers to generate the Enemark–Feltham designated {FeNO}<sup>8</sup> system. The synthesis of a thermally stable {FeNO}<sup>8</sup> species namely, [Co(Cp<sup>*</sup>)<sub>2</sub>][Fe(LN<sub>4</sub>)(NO)] (3), housed in a heme-like ...
    • ThermoSlope: A Software for Determining Thermodynamic Parameters from Single Steady-State Experiments 

      Lund, Bjarte Aarmo; Brandsdal, Bjørn Olav (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-11-26)
      The determination of the temperature dependence of enzyme catalysis has traditionally been a labourious undertaking. We have developed a new approach to the classical Arrhenius parameter estimation by fitting the change in velocity under a gradual change in temperature. The evaluation with a simulated dataset shows that the approach is valid. The approach is demonstrated as a useful tool by ...
    • The three Endonuclease III variants of Deinococcus radiodurans possess distinct and complementary DNA repair activities 

      Sarre, Aili; Stelter, Meike; Rollo, Filipe; De Bonis, Salvatore; Seck, Anna; Hognon, Cecilia; Ravanat, Jean-Luc; Monari, Antonio; Dehez, Francois; Moe, Elin; Timmins, Joanna (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-03-28)
      Endonuclease III (EndoIII) is a bifunctional DNA glycosylase that removes oxidized pyrimidines from DNA. The genome of Deinococcus radiodurans encodes for an unusually high number of DNA glycosylases, including three EndoIII enzymes (drEndoIII1-3). Here, we compare the properties of these enzymes to those of their well-studied homologues from E. coli and human. Our biochemical and mutational data, ...
    • To Bind or Not to Bind: Mechanistic Insights into C–CO2 Bond Formation with Late Transition Metals 

      García-López, Diego; Pavlovic, Ljiljana; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-03)
      In transition metal-mediated carboxylation reactions, CO<sub>2</sub> inserts into a metal–nucleophile bond. At the carboxylation transition state (TS), CO<sub>2</sub> may interact with the metal (<i>inner</i>-sphere path) or may insert without being activated by the metal (<i>outer</i>-sphere path). Currently, there is no consensus as to which path prevails. In order to establish general predictions ...
    • Total Synthesis of Phorbazole B 

      Guttormsen, Yngve; Fairhurst, Magnus John Espeland; Pandey, Sunil Kumar; Isaksson, Johan; Haug, Bengt Erik; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-21)
      Phorbazoles are polychlorinated heterocyclic secondary metabolites isolated from a marine sponge and several of these natural products have shown inhibitory activity against cancer cells. In this work, a synthesis of the trichlorinated phorbazole B using late stage electrophilic chlorination was developed. The synthesis relied on the use of an oxazole precursor, which was protected with an iodine ...
    • Total synthesis of tubastrine and 3-dehydroxy tubastrine by microwave-assisted cross-coupling reactions 

      Lorentzen, Marianne; Bayer, Annette; Sydnes, Magne Olav; Jørgensen, Kåre Bredeli (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-09-03)
      The first syntheses of tubastrine and 3-dehydroxy tubastrine are described. The target compounds were prepared in four consecutive steps from commercially available starting materials. The central scaffold was formed by a microwave-assisted C–N cross-coupling reaction between 1,3-bis(<i>tert</i>-butoxycarbonyl)-guanidine and (<i>E</i>)-((4-(2-iodovinyl)-1,2-phenylene)bis(oxy))bis(<i>tert</i>-butyl ...
    • Towards high-throughput screening (HTS) of polyhydroxyalkanoate (PHA) production via Fourier transform infrared (FTIR) spectroscopy of Halomonas sp. R5-57 and Pseudomonas sp. MR4-99 

      Christensen, Mikkel; Chiciudean, Iulia; Jablonski, Piotr; Tănase, Ana-Maria; Shapaval, Volha; Hansen, Hilde (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-03-08)
    • Towards Rational Computational Engineering of Psychrophilic Enzymes 

      Socan, Jaka; Isaksen, Geir Villy; Brandsdal, Bjørn Olav; Åqvist, Johan Lennart Gösta (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-12-16)
      Cold-adapted enzymes from psychrophilic species achieve their high catalytic efficiency at low temperature by a different partitioning of the activation free energy into its enthalpic and entropic components, compared to orthologous mesophilic enzymes. Their lower activation enthalpy, partly compensated by an increased entropic penalty, has been suggested to originate from changes in flexibility of ...
    • The Transition from Unfolded to Folded G-Quadruplex DNA Analyzed and Interpreted by Two-Dimensional Infrared Spectroscopy 

      Soenarjo, A Larasati; Lan, Zhihao; Sazanovich, Igor V.; Chan, Yee San; Ringholm, Magnus; Jha, Ajay; Klug, David R. (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-08-30)
      A class of DNA folds/structures known collectively as G-quadruplexes (G4) commonly forms in guanine-rich areas of genomes. G4-DNA is thought to have a functional role in the regulation of gene transcription and telomerase-mediated telomere maintenance and, therefore, is a target for drugs. The details of the molecular interactions that cause stacking of the guanine-tetrads are not well-understood, ...
    • Transition-Metal Isocorroles as Singlet Oxygen Sensitizers 

      Larsen, Simon; Adewuyi, Joseph A.; Ung, Gaël; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-05-04)
      Building on a highly efficient synthesis of pyrrole-appended isocorroles, we have worked out conditions for manganese, palladium, and platinum insertion into free-base 5/10-(2-pyrrolyl)-5,10,15-tris(4-methylphenyl)isocorrole, H<sub>2</sub>[5/10-(2-py)- TpMePiC]. Platinum insertion proved exceedingly challenging but was finally accomplished with cis-Pt(PhCN)<sub>2</sub>Cl<sub>2</sub>. All the ...
    • Twist-Bent Bonds Revisited: Adiabatic Ionization Potentials Demystify Enhanced Reactivity 

      Ghosh, Abhik; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-11)
      Explicit calculations of vertical and adiabatic ionization potentials of cyclopropane derivatives with modern DFT methods have underscored the possibility of unusually large reorganization energies (defined as the difference between vertical and adiabatic ionization potentials) of 0.5–1.0 eV for several compounds. Such is the case for ionization of the twist-bent σ-bond of trans-bicyclo[4.1.0]hept-3-ene ...
    • Two SnRK2-Interacting Calcium Sensor Isoforms Negatively Regulate SnRK2 Activity by Different Mechanisms 

      Tarnowski, Krzysztof; Klimecka, Maria; Ciesielski, Arkadiusz; Goch, Grazyna; Kulik, Anna; Fedak, Halina; Poznanski, Jaroslaw; Lichocka, Malgorzata; Pierechod, Marcin Miroslaw; Engh, Richard Alan; Dadlez, Michal; Dobrowolska, Grazyna; Bucholc, Maria (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-11-07)
      SNF1-related protein kinases 2 (SnRK2s) are key signaling elements regulating abscisic acid-dependent plant development and responses to environmental stresses. Our previous data showed that the SnRK2-interacting Calcium Sensor (SCS) inhibits SnRK2 activity. Use of alternative transcription start sites located within the Arabidopsis (Arabidopsis thaliana) AtSCS gene results in two in-frame transcripts ...
    • Two-Photon Absorption Cross-Sections in Fluorescent Proteins Containing Non-canonical Chromophores Using Polarizable QM/MM 

      Rossano-Tapia, Maria; Olsen, Jógvan Magnus Haugaard; Brown, Alex (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-12)
      Multi-photon absorption properties, particularly two-photon absorption (2PA), of fluorescent proteins (FPs) have made them attractive tools in deep-tissue clinical imaging. Although the diversity of photophysical properties for FPs is wide, there are some caveats predominant among the existing FP variants that need to be overcome, such as low quantum yields and small 2PA cross-sections. From a ...
    • Two-photon absorption in host-guest complexes 

      Alam, Mehboob; Ruud, Kenneth (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-17)
      We present an extensive analysis of one- and two-photon absorption processes in some organic host-guest (H-G) complexes using linear and quadratic response theory within the framework of time-dependent density functional theory. For this purpose, we have considered all possible 20 host-guest complexes constructed from 4 host and 5 guest molecules. We have analysed how the one- and two-photon activity ...