Search for dissertations about: "Per E. M. Siegbahn"

Showing result 1 - 5 of 6 swedish dissertations containing the words Per E. M. Siegbahn.

  2. 1. Biomimetic Transition Metal Catalysts : Insights from Theoretical Modeling

    Author : Adam Johannes Johansson; Per E. M. Siegbahn; Margareta R. A. Blomberg; Per-Ola Norrby; Stockholms universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Catalysis; biomimetic; copper; non-heme iron; heme iron; O2 cleavage; H-atom transfer; radical chemistry; redox chemistry; thermo chemistry; entropy calculations; quantum chemistry; spin states; density functional theory DFT ; self-interaction error SIE .; Chemical physics; Kemisk fysik; kemisk fysik; Chemical Physics;

    Abstract : The scientific interest in the chemistry of synthetic transition metal complexes is motivated by at least two arguments:1.These can be regarded as models of biological transition metal complexes, e.g. metalloenzymes, whose functions can be difficult to reveal in detail due to their complexity. READ MORE

  4. 2. Theoretical Modeling of Enzyme Catalysis with Focus on Radical Chemistry

    Author : Vladimir Pelmenschikov; Per E. M. Siegbahn; Tim Clark; Stockholms universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; density functional theory; enzyme catalysis; radical chemistry; zinc-containing peptidase; methyl-coenzyme M reductase; ribonucleotide reductase; superoxide dismutase; Quantum chemistry; Kvantkemi;

    Abstract : Hybrid density functional theory (DFT) B3LYP method is applied to study the four diverse enzyme systems: zinc-containing peptidases (thermolysin and stromelysin), methyl-coenzyme M reductase, ribonucleotide reductases (classes I and III), and superoxide dismutases (Cu,Zn- and Ni-dependent enzymes). Powerfull tools of modern quantum chemistry are used to address the questions of biological pathways at their molecular level, proposing a novel mechanism for methane production by methyl-coenzyme M reductase and providing additional insights into hydrolysis by zinc peptidases, substrate conversion by ribonucleotide reductases, and biological superoxide dismutation. READ MORE

  5. 3. Calculations of Reaction Mechanisms and Entropic Effects in Enzyme Catalysis

    Author : Masoud Kazemi; Johan Åqvist; Per E. M. Siegbahn; Uppsala universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Enzyme catalysis; Entropy; Cytidine deamination; Ribosome; Peptidyl-tRNA hydrolysis; Peptide bond formation; Empirical valence bond method; Density functional theory; Biology with specialization in Structural Biology; Biologi med inriktning mot strukturbiologi; Biokemi; Biochemistry; Biology with specialization in Molecular Biotechnology; Biologi med inriktning mot molekylär bioteknik;

    Abstract : Ground state destabilization is a hypothesis to explain enzyme catalysis. The most popular interpretation of it is the entropic effect, which states that enzymes accelerate biochemical reactions by bringing the reactants to a favorable position and orientation and the entropy cost of this is compensated by enthalpy of binding. READ MORE

  6. 4. Theoretical studies of mononuclear non-heme iron active sites

    Author : Arianna Bassan; Per E. M. Siegbahn; Sason Shaik; Stockholms universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; quantum chemistry; enzyme catalysis; iron enzymes; Quantum chemistry; Kvantkemi;

    Abstract : The quantum chemical investigations presented in this thesis use hybrid density functional theory to shed light on the catalytic mechanisms of mononuclear non-heme iron oxygenases, accommodating a ferrous ion in their active sites. More specifically, the dioxygen activation process and the subsequent oxidative reactions in the following enzymes were studied: tetrahydrobiopterin-dependent hydroxylases, naphthalene 1,2-dioxygenase and α-ketoglutarate-dependent enzymes. READ MORE

  7. 5. Reaction Mechanisms of Metalloenzymes and Synthetic Model Complexes Activating Dioxygen : A Computational study

    Author : Valentin Georgiev; Per E.M. Siegbahn; Sam de Visser; Stockholms universitet; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; catalysis; density functional theory; extradiol; intradiol; dioxygenases; oxygen; biomimetic complexes; heme; spin transition; adipic acid; Chemical physics; Kemisk fysik; kvantkemi; Quantum Chemistry;

    Abstract : Quantum chemistry has nowadays become a powerful and efficient tool that can be successfully used for studies of biosystems. It is therefore possibleto model the enzyme active-site and the reactions undergoing into it, as well as obtaining quite accurate energetic profiles. READ MORE