Now showing items 181-200 of 527

    • 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 ...
    • 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 ...
    • Microwave‐Assisted Synthesis of Heterocycles from Aryldiazoacetates 

      Kristoffersen, Tone; Elumalai, Vijayaragavan; Starck, Eliot; Cousin, Étienne; Hansen, Stephanie Ramona; Hansen, Jørn H (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-17)
      Herein, we describe a rapid microwave-assisted, metal-free synthesis of substituted quinoxalinones and quinoxalines using the carbene-mediated reaction between aryldiazo esters and 1,2-diamines. The reaction can encompass a range of substituents and structural variations to afford quinoxalin-2-ones in 14–80 % yield and corresponding quinoxalines in good to excellent yields upon oxidation (67–96 %). ...
    • Behind the scenes of spin-forbidden decay pathways in transition metal complexes 

      Moitra, Torsha; Karak, Pijush; Chakraborty, Sayantani; Ruud, Kenneth; Chakrabarti, Swapan (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-10)
      The interpretation of the ultrafast photophysics of transition metal complexes following photo-absorption is quite involved as the heavy metal center leads to a complicated and entangled singlet–triplet manifold. This opens up multiple pathways for deactivation, often with competitive rates. As a result, intersystem crossing (ISC) and phosphorescence are commonly observed in transition metal complexes. ...
    • Computational and experimental insights into asymmetric Rh‐catalyzed hydrocarboxylation with CO2 

      Pavlovic, Ljiljana; Pettersen, Martin; Gevorgyan, Ashot; Vaitla, Janakiram; Bayer, Annette; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-18)
      The asymmetric Rh‐catalyzed hydrocarboxylation of α,β‐unsaturated carbonyl compounds was originally developed by Mikami and co‐workers but gives only moderate enantiomeric excesses. In order to understand the factors controlling the enantioselectivity and to propose novel ligands for this reaction, we have used computational and experimental methods to study the Rh‐catalyzed hydrocarboxylation with ...
    • Rhenium-Imido Corroles 

      Alemayehu, Abraham; Teat, Simon J.; Borisov, Sergey M.; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-04-10)
      Metallocorroles involving 5d transition metals are currently of interest as near-IR phosphors and as photosensitizers for oxygen sensing and photodynamic therapy. Their syntheses, however, are often bedeviled by capricious and low-yielding protocols. Against this backdrop, we describe rhenium-imido corroles, a new class of 5d metallocorroles, synthesized simply and in respectable (∼30%) yields via ...
    • Organometallic Chemistry for Enabling Carbon Dioxide Utilization 

      Hazari, Nilay; Iwasawa, Nobuharu; Hopmann, Kathrin Helen (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-05-11)
      <p>In photosynthesis, carbon dioxide is used as the carbon source; indeed, most carbon atoms in the structure of a massive tree—the trunk, the branches, the leaves—originate from CO2. This insight has profound implications for chemical synthesis: complex molecular structures are built from something as simple and inert as CO<sub>2</sub>. Scientists have long been fascinated by this concept, and ...
    • Renewable Solvents for Palladium-Catalyzed Carbonylation Reactions 

      Ismael, Aya; Gevorgyan, Ashot; Skrydstrup, Troels; Bayer, Annette (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-04)
      Solvents constitute the largest component for many chemical processes and substitution of nonrenewable solvents is a longstanding goal for green chemistry. Here, we show that Pd-catalyzed carbonylative couplings, such as carbonylative cross-couplings, aminocarbonylations, and alkoxycarbonylations, can be successfully realized using renewable solvents. The present research covers not only well-established ...
    • General recurrence-relation generation scheme for molecular integral evaluation 

      Gao, Bin (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-24)
      We develop a new scheme for evaluating different molecular integrals using Gaussian type orbitals. In this new scheme, the evaluation of integrals is performed in two steps during runtime. The first step is a top-down procedure that maps each recurrence relation into a jagged array (array of arrays), where each element of a member array represents either the final results or some intermediate integrals ...
    • Effects of fecal microbiota transplantation in subjects with irritable bowel syndrome are mirrored by changes in gut microbiome 

      Goll, Rasmus; Johnsen, Peter Holger; Hjerde, Erik; Diab, Joseph; Valle, Per Christian; Hilpüsch, Frank; Cavanagh, Jorunn Pauline (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-09-29)
      Irritable bowel syndrome (IBS) is a common disorder of the lower gastrointestinal tract. The pathophysiology is far from settled, but a gut microbial dysbiosis is hypothesized to be a contributing factor. We earlier published a randomized double-blind placebo-controlled clinical trial on fecal microbiota transplantation (FMT) for IBS – the REFIT trial. The present data set describes the engraftment ...