Challenges in Enzyme Catalysis - Photosystem II and Orotidine Decarboxylase: A Density Functional Theory Treatment
2005 (English)Doctoral thesis, comprehensive summary (Other academic)Text
Possibly the most fascinating biochemical mechanism remaining to be solved is the formation of oxygen from water in photosystem II. This is a critical part of the photosynthetic reaction that makes solar energy accessible to living organisms.
The present thesis uses quantum chemistry, more specifically the density functional B3LYP, to investigate a mechanism where an oxyl radical bound to manganese is the active species in O-O bond formation. Benchmark calculations on manganese systems confirm that B3LYP can be expected to give accurate results. The effect of the self-interaction error is shown to be limited. Studies of synthetic manganese complexes support the idea of a radical mechanism. A manganese complex with an oxyl radical is active in oxygen formation while manganese-oxo complexes remain inactive. Formation of the O-O bond requires a spin transition but there should be no effect on the rate. Spin transitions are also required in many short-range electron-transfer reactions.
Investigations of the superproficient enzyme orotidine decarboxylase support a mechanism that involves an invariant network of charged amino acids, acting together with at least two mobile water molecules.
Place, publisher, year, edition, pages
Stockholm: Fysikum, Stockholms universitet , 2005. , 77 p.
IdentifiersURN: urn:nbn:se:uu:diva-276494ISBN: 91-7155-057-7OAI: oai:DiVA.org:uu-276494DiVA: diva2:903197