Dokument: Investigation of the active site of the [FeFe] hydrogenase from Desulfovibrio desulfuricans
| Titel: | Investigation of the active site of the [FeFe] hydrogenase from Desulfovibrio desulfuricans | |||||||
| URL für Lesezeichen: | https://docserv.uni-duesseldorf.de/servlets/DocumentServlet?id=5143 | |||||||
| URN (NBN): | urn:nbn:de:hbz:061-20070711-110344-7 | |||||||
| Kollektion: | Dissertationen | |||||||
| Sprache: | Englisch | |||||||
| Dokumententyp: | Wissenschaftliche Abschlussarbeiten » Dissertation | |||||||
| Medientyp: | Text | |||||||
| Autor: | Silakov, Alexey [Autor] | |||||||
| Dateien: |
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| Beitragende: | Prof. Dr. Lubitz, Wolfgang [Gutachter] Prof. Dr. Büldt, Georg [Gutachter] | |||||||
| Dewey Dezimal-Klassifikation: | 500 Naturwissenschaften und Mathematik » 540 Chemie | |||||||
| Beschreibung: | Alexey Evgenievich Silakov
Hydrogen plays an important role in the metabolism of certain microorganisms, where the reaction H2 = 2H+ + 2e− is catalyzed by metalloenzymes called hydrogenases. The active site of the [FeFe] hydrogenase (the so called H-cluster) contains a classical [4Fe4S] cluster connected via the sulphur of a cysteine residue to a bi-nuclear cluster. The [2Fe]H subcluster is coordinated by CO and CN ligands, which stabilize metals in low-oxidation states. Several states of the active site can be detected using EPR. The oxidized form of the H-cluster (Hox) shows a very characteristic rhombic EPR spectrum. The distal iron of the [2Fe]H subcluster has an exchangeable coordination site. Upon inhibition of the protein by CO, this coordination site is occupied by the CO ligand (the so-called Hox-CO state). In this case an axial EPR signal is observed. In this thesis, the active site of the [FeFe] hydrogenase from the Desulfovibrio desulfuricans was investigated in various states. The electronic structure of the Hcluster was studied using CW EPR and advanced pulse EPR techniques including Davies- ENDOR, and HYSCORE. The nuclear spin interactions of the 1H, 13C, 14N and 57Fe nuclei were determined. It was found that the Hox-CO state is characterized by a rather strong [2Fe]H-[4Fe4S]H exchange interaction and moderate localization of the unpaired spin on the bi-nuclear subcluster. In contrast, the exchange interaction in the Hox state is much weaker. The unpaired spin density was found to be almost equally distributed over the iron atoms of the bi-nuclear subcluster. These facts point to large changes in the electronic structure of the H-cluster upon inhibition by CO. The light induced conversion of the Hox-CO state has been studied as a function of the excitation wavelength at low temperature (40 K). Two additional species were detected by EPR during illumination. Investigation of the wavelength dependence of the photo-dissociation conversion rates shows, that this dependence is related to the optical absorption spectrum of the [FeFe] hydrogenase. In order to characterize the light-induced species, they were examined for the first time by advanced EPR spectroscopy. One of these species has been identified as the Hox state. The other species is characterized by an EPR spectrum with large rhombicity. According to earlier FT-IR studies, the second species most probably has lost the bridging CO ligand. However, the study presented in this thesis suggests that the former bridging CO ligand is in the terminal position of one of the irons of the binuclear subcluster. The investigation of the electronic structure of the second light induced species reveals, that in terms of the exchange coupling this state is intermediate between the Hox and the Hox-CO states. | |||||||
| Lizenz: |  Urheberrechtsschutz | |||||||
| Fachbereich / Einrichtung: | Mathematisch- Naturwissenschaftliche Fakultät | |||||||
| Dokument erstellt am: | 11.07.2007 | |||||||
| Dateien geändert am: | 11.07.2007 | |||||||
| Promotionsantrag am: | 25.12.2006 | |||||||
| Datum der Promotion: | 17.01.2007 |
