Now showing items 101-120 of 611

    • Conformational tuning improves the stability of spirocyclic nitroxides with long paramagnetic relaxation times 

      Sowinski, Mateusz; Gahlawat, Sahil; Lund, Bjarte Aarmo; Warnke, Anna-Luisa; Hopmann, Kathrin Helen; Lovett, Janet E.; Haugland, Marius Myreng (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-06-05)
      Nitroxides are widely used as probes and polarization transfer agents in spectroscopy and imaging. These applications require high stability towards reducing biological environments, as well as beneficial relaxation properties. While the latter is provided by spirocyclic groups on the nitroxide scaffold, such systems are not in themselves robust under reducing conditions. In this work, we introduce ...
    • Automatisk rettet eksamen i generell kjemi 

      Beerepoot, Maarten; Kosonen, Juho A. (Conference object; Konferansebidrag, 2023-03)
      En god avsluttende eksamen vurderer i hvilken grad intendert læringsutbytte har blitt oppnådd på en nøye, objektiv og reproduserbar måte. Det er imidlertid lite tilfredsstillende hvis en faglærer bruker mye tid på vurdering avlæring framfor vurdering forlæring underveis i semesteret. Derfor kan det være attraktivtå utforske muligheter med en digital automatisk rettet ...
    • Exact Two-Component TDDFT with Simple Two-Electron Picture-Change Corrections: X-ray Absorption Spectra Near L- and M-Edges of Four-Component Quality at Two-Component Cost 

      Konecny, Lukas; Komorovsky, Stanislav; Vicha, Jan; Ruud, Kenneth; Repisky, Michal (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-01)
      X-ray absorption spectroscopy (XAS) has gained popularity in recent years as it probes matter with high spatial and elemental sensitivities. However, the theoretical modeling of XAS is a challenging task since XAS spectra feature a fine structure due to scalar (SC) and spin–orbit (SO) relativistic effects, in particular near L and M absorption edges. While full four-component (4c) calculations of ...
    • Mechanistic Investigations of the Asymmetric Hydrogenation of Enamides with Neutral Bis(phosphine) Cobalt Precatalysts 

      Mendelsohn, Lauren N.; Pavlovic, Ljiljana; Zhong, Hongyu; Friedfeld, Max R.; Shevlin, Michael; Hopmann, Kathrin Helen; Chirik, Paul J. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-11)
      The mechanism of the asymmetric hydrogenation of prochiral enamides by well-defined, neutral bis(phosphine) cobalt(0) and cobalt(II) precatalysts has been explored using(R,R)-<sup>iPr</sup>DuPhos ((R,R)-<sup>iPr</sup>DuPhos = (+)-1,2-bis[(2R,5R)-2,5-diisopropylphospholano]benzene) as a representative chiral bis(phosphine) ligand. A series of (R,R)-(<sup>iPr</sup>DuPhos)Co(enamide) (enamide = ...
    • Development of potent cholinesterase inhibitors based on a marine pharmacophore 

      Elumalai, Vijayaragavan; Trobec, Tomaz; Grundner, Maja; Labriere, Christophe; Frangez, Robert; Sepcic, Kristina; Hansen, Jørn H; Svensson, Johan (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-01)
      The management of neurological disorders such as dementia associated with Alzheimer's or Parkinson's disease includes the use of cholinesterase inhibitors. These compounds can slow down the progression of these diseases and can also be used in the treatment of glaucoma and myasthenia gravis. The majority of the cholinesterase inhibitors used in the clinic are derived from natural products and our ...
    • The Hyperporphyrin Concept: A Contemporary Perspective 

      Wamser, Carl C.; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-30)
      The Gouterman four-orbital model conceptualizes porphyrin UV−visible spectra as dominated by four frontier molecular orbitals-two nearly degenerate HOMOs and two exactly degenerate LUMOS under D<sub>4h</sub> symmetry. These are well separated from all the other molecular orbitals, and normal spectra involve transitions among these MOs. Unusual spectra occur when additional orbitals appear in ...
    • Crystal Structure Evolution of Fluorine under High Pressure 

      Tantardini, Christian; Jalolov, Faridun N.; Kvashnin, Alexander G. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-01)
      Fluorinated compounds in the last decade were applied as photothermo-refractive glasses, high-stress lubricants, and pharmaceutical drugs due to their good mechanical properties and biocompatibility. Although fluorinated materials are largely employed, the possibility of predicting new structures was limited by the impossibility to use density functional theory (DFT) to describe interatomic ...
    • Electronic effects on the mechanism of the NAD+ coenzyme reduction catalysed by a non-organometallic ruthenium(ii) polypyridyl amine complex in the presence of formate 

      Chrzanowska, Marta; Katafias, Anna; van Eldik, Rudi; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-01)
      In the present study, electronic effects on the mechanism of the NAD+ coenzyme reduction in the presence of formate, catalysed by a non-organometallic ruthenium(II) polypyridyl amine complex, were investigated. The [RuII(terpy)(ampy)Cl]Cl (terpy ¼ 2,20 :60 ,200-terpyridine, ampy ¼ 2-(aminomethyl)pyridine) complex was employed as the catalyst. The reactions were studied in a water/ethanol mixture ...
    • Promising Nanocarriers to Enhance Solubility and Bioavailability of Cannabidiol for a Plethora of Therapeutic Opportunities 

      Grifoni, Lucia; Vanti, Giulia; Donato, Rosa; Sacco, Cristiana; Bilia, Anna Rita (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-17)
      In recent years, the interest in cannabidiol (CBD) has increased because of the lack of psychoactive properties. However, CBD has low solubility and bioavailability, variable pharmacokinetics profiles, poor stability, and a pronounced presystemic metabolism. CBD nanoformulations include nanosuspensions, polymeric micelles and nanoparticles, hybrid nanoparticles jelled in cross-linked chitosan, and ...
    • A Computational Protocol for Vibrational Circular Dichroism Spectra of Cyclic Oligopeptides 

      Eikås, Karolina Solheimslid; Beerepoot, Maarten; Ruud, Kenneth (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-08-05)
      Cyclic peptides are a promising class of compounds for next-generation antibiotics as they may provide new ways of limiting antibiotic resistance development. Although their cyclic structure will introduce some rigidity, their conformational space is large and they usually have multiple chiral centers that give rise to a wide range of possible stereoisomers. Chiroptical spectroscopies such as ...
    • Metallaaromaticity - a protean world 

      Cuyacot, Ben Joseph R.; Badri, Zahra; Ghosh, Abhik; Foroutan-Nejad, Cina (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-01)
      The nature of magnetically induced current densities (MICD) of metallabenzenes and related compounds has been examined with relativistic DFT calculations to assess the magnetic aromaticity of the molecules. The origin of the total MICD has been analyzed in terms of individual molecular orbital (MO) contributions. Our study reveals that the s-framework of the molecules always makes a diamagnetic ...
    • Phenol- and resorcinol-appended metallocorroles and their derivatization with fluorous tags 

      Alemayehu, Abraham; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-10)
      Boron tribromide-mediated demethylation of rhenium-oxo and gold meso-tris(4-methoxyphenyl)corrole and meso-tris(3,5-dimethoxyphenylcorrole), M[TpOMePC] and M[T(3,5-OMe)PC] (M = ReO, Au), have yielded the corresponding phenol- and resorcinol-appended metallocorroles, M[TpOHPC] and M[T(3,5-OH)PC], in good yields. The latter compounds proved insoluble in dichloromethane and chloroform but soluble in ...
    • Spin-vibronic interaction induced reverse intersystem crossing: A case study with TXO-TPA and TXO-PhCz molecules 

      Karak, Pijush; Ruud, Kenneth; Chakrabarti, Swapan (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-01)
      We highlight the important roles the direct spin–orbit (DSO) coupling, the spin-vibronic (SV) coupling, and the dielectric constant of the medium play on the reverse intersystem crossing (RISC) mechanism of TXO-TPA and TXO-PhCz molecules. To understand this complex phenomenon, we have calculated the RISC rate constant, kRISC, using a time-dependent correlation function-based method within the framework ...
    • Porphyryne 

      Ghosh, Abhik; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-25)
      Density functional theory calculations with the B3LYP*-D3 method with large STO-QZ4P basis sets unambiguously predict a singlet ground state for Zn-porphyryne. However, the calculations also predict a low singlet–triplet gap of about 0.4 eV and a high adiabatic electron affinity of 2.4 eV. Accordingly, the reactivity of porphyryne species may be dominated by electron transfer, hydrogen abstraction, ...
    • DFT studies of the redox behavior of oligo(aza)pyridines and experimental CVs of 4′-substituted terpyridines 

      Mateyise, Nandisiwe Ghandi Sibongile; Conradie, Marrigje M.; Conradie, Jeanet (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-11-17)
      The cyclic voltammograms of a series of substituted terpyridine ligands are presented, showing that reduction occur generally below −2 V versus the redox potential of ferrocene. Density functional theory (DFT) calculated energies and the theoretically calculated reduction potentials of a large series of substituted oligo(aza)pyridine ligands (terpyridine, bipyridine and phenanthroline) are determined ...
    • A unique class I polyhydroxyalkanoate synthase (PhaC) from Brevundimonas sp. KH11J01 exists as a functional trimer: A comparative study with PhaC from Cupriavidus necator H16 

      Assefa, Netsanet Gizaw; Hansen, Hilde; Altermark, Bjørn (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-06)
      Polyhydroxyalkanoates (PHAs) are natural biodegradable polyesters that are produced by numerous prokaryotic microorganisms primarily as a carbon- and energy reserve. The PhaC enzyme catalyzes the last step in the PHA biosynthesis pathway and synthesizes PHA polymers from hydroxyalkanoic acids. A type I PhaC from a PHAproducing marine bacterium Brevundimonas sp. KH11J01 (BrPhaC) was identified, ...
    • Mobile group I introns at nuclear rDNA position L2066 harbor sense and antisense homing endonuclease genes intervened by spliceosomal introns 

      Lian, Kjersti; Furulund, Betty Martine Normann; Tveita, Anders Aune; Haugen, Peik; Johansen, Steinar Daae (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-10-08)
      Background: Mobile group I introns encode homing endonucleases that confer intron mobility initiated by a double-strand break in the intron-lacking allele at the site of insertion. Nuclear ribosomal DNA of some fungi and protists contain mobile group I introns harboring His-Cys homing endonuclease genes (HEGs). An intriguing question is how protein-coding genes embedded in nuclear ribosomal DNA ...
    • Vibrational Corrections to NMR Spin-Spin Coupling Constants from Relativistic Four-Component DFT Calculations 

      Jakubowska, Katarzyna; Pecul, Magdalena; Ruud, Kenneth (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-09-22)
      Zero-point vibrational (ZPV) corrections to the nuclear spin–spin coupling constants have been calculated using four-component Dirac–Kohn–Sham DFT for H<sub>2</sub>X (where X = O, S, Se, Te, Po), XH<sub>3</sub> (where X = N, P, As, Sb, Bi), and XH<sub>4</sub> (where X = C, Si, Ge, Sn, and Pb) molecules and for HC≡CPbH<sub>3</sub>. The main goal was to study the influence of relativistic effects on ...
    • Structural Organization of S516 Group I Introns in Myxomycetes 

      Furulund, Betty Martine Normann; Karlsen, Bård Ove; Babiak, Igor; Haugen, Peik; Johansen, Steinar Daae (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-05-25)
      Group I introns are mobile genetic elements encoding self-splicing ribozymes. Group I introns in nuclear genes are restricted to ribosomal DNA of eukaryotic microorganisms. For example, the myxomycetes, which represent a distinct protist phylum with a unique life strategy, are rich in nucleolar group I introns. We analyzed and compared 75 group I introns at position 516 in the small subunit ...
    • Iridium(VII)-Corrole Terminal Carbides Should Exist as Stable Compounds 

      Alemayehu, Abraham; Conradie, Jeanet; Ghosh, Abhik (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-14)
      Scalar-relativistic DFT calculations with multiple exchangecorrelation functionals and large basis sets foreshadow the existence of stable iridium(VII)−corrole terminal carbide derivatives. For the parent compound Ir[Cor](C), OLYP/STO-TZ2P calculations predict a short Ir− C bond distance of 1.69 Å, a moderately domed macrocycle with no indications of ligand noninnocence, a surprisingly low ...