Now showing items 181-200 of 581

    • Structural and biochemical characterization of the environmental MBLs MYO-1, ECV-1 and SHD-1 

      Frøhlich, Christopher; Sørum, Vidar; Huber, Sandra; Samuelsen, Ørjan; Berglund, Fanny; Kristiansson, Erik; Kotsakis, Stathis D.; Marathe, Nachiket; Larsson, DG Joakim; Leiros, Hanna-Kirsti Schrøder (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-28)
      Background: MBLs form a large and heterogeneous group of bacterial enzymes conferring resistance to b-lactam antibiotics, including carbapenems. A large environmental reservoir of MBLs has been identified, which can act as a source for transfer into human pathogens. Therefore, structural investigation of environmental and clinically rare MBLs can give new insights into structure–activity relationships ...
    • A Green, Scalable, and Catalyst-Free One-Minute Synthesis of Quinoxalines 

      Elumalai, Vijayaragavan; Hansen, Jørn H (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-10)
      A highly efficient and catalyst-free protocol is reported for the synthesis of quinoxalines via the classical cyclocondensation reaction between aryldiamines and dicarbonyl compounds. Remarkably simple and green reaction conditions employing methanol as solvent afforded medium to excellent yield of quinoxalines after only one-minute reaction time at ambient temperature. The conditions allow at least ...
    • Improved Buchwald–Hartwig Amination by the Use of Lipids and Lipid Impurities 

      Gevorgyan, Ashot; Hopmann, Kathrin Helen; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-10-25)
      The development of green Buchwald–Hartwig aminations has long been considered challenging, due to the high sensitivity of the reaction to the environment. Here we show that food-grade and waste vegetable oils, triglycerides originating from animals, and natural waxes can serve as excellent green solvents for Buchwald–Hartwig amination. We further demonstrate that amphiphiles and trace ingredients ...
    • Halogen Bonding: An Odd Chemistry? 

      Turunen, Lotta; Hansen, Jørn H; Erdélyi, Máté (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-03)
      Halogen bonding is a flourishing field of research, but has for long been little recognized. The same goes for its scientific hero, Odd Hassel, who laid the foundations for all current developments. The crystallographic observation of halogen−oxygen interatomic distances shorter than the sum of the van der Waals radii of the involved atoms, and the interpretation of this phenomenon as a charge-transfer ...
    • Nature of the copper-nitrosyl intermediates of copper nitrite reductases during catalysis 

      Ghosh, Abhik; Conradie, Jeanet; Strange, Richard W; Antonyuk, Svetlana V; Eady, Robert R; Hasnain, Samar (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-20)
      The design and synthesis of copper complexes that can reduce nitrite to NO has attracted considerable interest. They have been guided by the structural information on the catalytic Cu centre of the widespread enzymes Cu nitrite reductases but the chemically novel side-on binding of NO observed in all crystallographic studies of these enzymes has been questioned in terms of its functional relevance. ...
    • Gruppelærerdagen – trygghet og kvalitet fra første undervisningstime 

      Huru, Hilja Lisa; Beerepoot, Maarten (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-24)
      En stor del av undervisningen i realfagene ved norske universiteter blir utført av stipendiater eller studenter fra tidligere kull. Fokus på opplæring av denne gruppen undervisere kan bidra til en positiv effekt på undervisningskvalitet og studentenes læring. Det varierer imidlertid fra institusjon til institusjon om det finnes en slik type opplæring og omfang og kvalitet på denne opplæringen kan ...
    • Harmonic Infrared and Raman Spectra in Molecular Environments Using the Polarizable Embedding Model 

      Dundas, Karen Oda Hjorth Minde; Beerepoot, Maarten T. P.; Ringholm, Magnus; Reine, Simen Sommerfelt; Bast, Radovan; List, Nanna Holmgaard; Kongsted, Jacob; Ruud, Kenneth; Olsen, Jógvan Magnus Haugaard (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-19)
      We present a fully analytic approach to calculate infrared (IR) and Raman spectra of molecules embedded in complex molecular environments modeled using the fragment-based polarizable embedding (PE) model. We provide the theory for the calculation of analytic second-order geometric derivatives of molecular energies and first-order geometric derivatives of electric dipole moments and dipole–dipole ...
    • A Green, Scalable, One-Minute Synthesis of Benzimidazoles 

      Elumalai, Vijayaragavan; Hansen, Jørn H (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-24)
      Herein is reported a substantially improved synthesis of 2-substituted benzimidazoles by condensation of 1,2-diaminoarenes and aldehydes using methanol as the reaction medium. The developed method afforded moderate to excellent yields (33-96%) at ambient temperature, displays high functional group tolerance, is conducted open to air, and requires only one-minute reaction time under catalyst- ...
    • Ni(I)–Alkyl Complexes Bearing Phenanthroline Ligands: Experimental Evidence for CO2 Insertion at Ni(I) Centers 

      Somerville, Rosie J.; Odena, Carlota; Obst, Marc; Hazari, Nilay; Hopmann, Kathrin Helen; Martin, Ruben (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-06-10)
      Although the catalytic carboxylation of unactivated alkyl electrophiles has reached remarkable levels of sophistication, the intermediacy of (phenanthroline)Ni(I)–alkyl species—complexes proposed in numerous Ni-catalyzed reductive cross-coupling reactions—has been subject to speculation. Herein we report the synthesis of such elusive (phenanthroline)Ni(I) species and their reactivity with CO<sub>2</sub>, ...
    • Structural and functional variation of chitin-binding domains of a lytic polysaccharide monooxygenase from Cellvibrio japonicus 

      Madland, Eva; Forsberg, Zarah; Wang, Yong; Lindorff-Larsen, Kresten; Niebisch, Axel; Modregger, Jan; Eijsink, Vincent; Aachmann, Finn Lillelund; Courtade, Gaston (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-17)
      Among the extensive repertoire of carbohydrate-active enzymes, lytic polysaccharide monooxygenases (LPMOs) have a key role in recalcitrant biomass degradation. LPMOs are copper-dependent enzymes that catalyze oxidative cleavage of glycosidic bonds in polysaccharides such as cellulose and chitin. Several LPMOs contain carbohydrate-binding modules (CBMs) that are known to promote LPMO efficiency. ...
    • The Pseudoalteromonas multipartite genome: distribution and expression of pangene categories, and a hypothesis for the origin and evolution of the chromid 

      Sonnenberg, Cecilie Bækkedal; Haugen, Peik (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-21)
      Bacterial genomes typically consist of one large chromosome, but can also include secondary replicons. These so-called multipartite genomes are scattered on the bacterial tree of life with the majority of cases belonging to Proteobacteria. Within the class gamma-proteobacteria, multipartite genomes are restricted to the two families <i>Vibrionaceae</i> and <i>Pseudoalteromonadaceae</i>. Whereas the ...
    • Computer Modelling of an Enzyme Reference Reaction for Empirical Valence Bond Simulation 

      Abdulyaqeen, Uthman Seyi (Master thesis; Mastergradsoppgave, 2020-11-04)
      It is extensively recognized that an enzyme functions through reducing the energy of activation of its elemental reaction and the catalytic effect of an enzyme is as a result of a change in activation free energy obtained relative to a reference reaction in water of the same mechanism. In this study, chorismate mutase which is an enzyme that catalyzes biochemical reactions for chorismate conversion ...
    • Antibiotic Resistance Breakers: Design and Synthesis of OXA-48 Inhibitors 

      Magnussen, Harald (Master thesis; Mastergradsoppgave, 2020-06-01)
      Antibiotic resistance is threatening the achievements of modern medicine and will evidentially lead to a situation, in which we stand helpless against common bacterial infections. The largest and most widely used group of antibiotics are the β-lactams. One of the major resistance determinants against β-lactam antibiotics is the expression of hydrolytic enzymes, called β-lactamases (BLs). The main ...
    • Lipids as Versatile Solvents for Chemical Synthesis 

      Gevorgyan, Ashot; Hopmann, Kathrin Helen; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-23)
      Development of safe, renewable, cheap and versatile solvents is a longstanding challenge in chemistry. We show here that vegetable oils and related systems can become prominent solvents for organic synthesis. Suzuki–Miyaura, Hiyama, Stille, Sonogashira and Heck cross-couplings proceed with quantitative yields in a range of vegetable oils, fish oil, butter and waxes used as solvents. Appropriate ...
    • Bacteriophage origin of some minimal ATP-dependent DNA ligases: a new structure from Burkholderia pseudomallei with striking similarity to Chlorella virus ligase 

      Pan, Jolyn; Lian, Kjersti; Sarre, Aili; Leiros, Hanna-Kirsti Schrøder; Williamson, Adele Kim (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-09-21)
      DNA ligases, the enzymes responsible for joining breaks in the phosphodiester backbone of DNA during replication and repair, vary considerably in size and structure. The smallest members of this enzyme class carry out their functions with pared-down protein scaffolds comprising only the core catalytic domains. Here we use sequence similarity network analysis of minimal DNA ligases from all biological ...
    • Biochemical and biophysical characterization of the OXA-48-like carbapenemase OXA-436 

      Lund, Bjarte Aarmo; Thomassen, Ane Molden; Carlsen, Trine Josefine Warg; Leiros, Hanna-Kirsti Schrøder (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-08-31)
      The crystal structure of the class D β-lactamase OXA-436 was solved to a resolution of 1.80 Å. Higher catalytic rates were found at higher temperatures for the clinically important antibiotic imipenem, indicating better adaptation of OXA-436 to its mesophilic host than OXA-48, which is believed to originate from an environmental source. Furthermore, based on the most populated conformations during ...
    • Chemical Analysis and Anthelmintic Activity Against Teladorsagia Circumcincta of Nordic Bark Extracts In vitro 

      Athanasiadou, Spiridoula; Almvik, Marit; Hellström, Jarkko; Madland, Eva; Simic, Nebojsa; Steinshamn, Håvard (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-04)
      Helminth parasitic infections are common in small ruminants in Norway; infection is usually treated with anthelmintic drugs, but anthelmintic resistance is an increasing problem. It is necessary to identify strategies to reduce the use of anthelmintic drugs and mitigate the impact of anthelmintic resistance. Condensed tannin (CT)-rich forages have been shown to reduce the helminth burden in small ...
    • Cryptic β-Lactamase Evolution Is Driven by Low β-Lactam Concentrations 

      Fröhlich, Christopher; Gama, João Alves; Harms, Klaus; Hirvonen, Viivi H. A.; Lund, Bjarte Aarmo; van der Kamp, Marc W.; Johnsen, Pål Jarle; Samuelsen, Ørjan; Leiros, Hanna-Kirsti S. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-28)
      Our current understanding of how low antibiotic concentrations shape the evolution of contemporary β-lactamases is limited. Using the widespread carbapenemase OXA-48, we tested the long-standing hypothesis that selective compartments with low antibiotic concentrations cause standing genetic diversity that could act as a gateway to developing clinical resistance. Here, we subjected <i>Escherichia ...
    • Complete genome sequence of Photobacterium ganghwense C2.2: A new polyhydroxyalkanoate production candidate 

      Lascu, Irina; Mereuță, Ioana; Chiciudean, Iulia; Hansen, Hilde; Avramescu, Sorin Marius; Tănase, Ana-Maria; Stoica, Ileana (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-05-01)
      Polyhydroxyalkanoates (PHAs) are biodegradable bioplastics that can be manufactured sustainably and represent a promising green alternative to petrochemical-based plastics. Here, we describe the complete genome of a new marine PHA-producing bacterium—Photobacterium ganghwense (strain C2.2), which we have isolated from the Black Sea seashore. This new isolate is psychrotolerant and accumulates PHA ...
    • Evolution of β-lactamases and enzyme promiscuity 

      Fröhlich, Christopher; Chen, John Z; Gholipour, Sevan; Erdogan, Ayse N; Tokuriki, Nobuhiko (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-08)
      β-Lactamases represent one of the most prevalent resistance mechanisms against β-lactam antibiotics. Beyond their clinical importance, they have also become key models in enzymology and evolutionary biochemistry. A global understanding of their evolution and sequence and functional diversity can therefore aid a wide set of different disciplines. Interestingly, β-lactamases have evolved multiple times ...