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Freie Universität Berlin

1. Pudollek, Susanne. Multifrequency EPR and ENDOR spectroscopy of the S2-state of the manganese complex in photosystem II.

Degree: 2012, Freie Universität Berlin

Plants, green algae and cyanobacteria alike use oxygenic photosynthesis to transform harvested light into chemical energy. The oxygen which is released from oxidised water molecules forms the basis of animal and human life. The reaction cycle of catalytic dissociation of the water molecules takes place within a large protein complex called Photosystem II (PSII). Its catalytic center is the WaterOxidizing Complex (WOC) comprising four manganese and a calcium ion. The underlying reaction mechanism is not yet understood. The requisite for the development of appropriate models to explain its behavior is an accurate knowledge of its structure and physical/chemical properties in every step of the catalytic cycle. Electron Paramagnetic Resonance (EPR) and related methods employ the interaction between unpaired electrons in an external magnetic field by measurement of their spin state‚Äôs energy splitting. The observed energy differences carry information about the paramagnetic center and its immediate surrounding. Hence, this method is perfectly suited to selectively investigate the paramagnetic S2-state of the WOC within PSII. Initially, the capabilities and benefits of multi-frequency EPR and ENDOR were demonstrated on a di-manganese model system, Mn-Catalase, studying its characteristics and magnetic parameters. These methods then were transferred onto the WOC S2-state in native PSII from cyanobacterium Thermosynechococcus elongatus and onto the same system, but grown in nutrient containing strontium exclusively, which is the only known functional replacement for calcium. In comparison to native PSII, the S2-state of PSII-Sr exhibits changes in its EPR and ENDOR spectra. To date, these are insufficiently characterized. By means of multi-frequency EPR and ENDOR investigation of both systems in solution, their properties could be determined. Q-band EPR and 55Mn-ENDOR spectroscopy on native PSII crystals allowed for an assignment not only of the fundamental components of the 55Mn hyperfine couplings, but also of their orientations within the crystal frame. In analogy to structural motives from said di- manganese model systems, correlations between magnetic parameters and local structural characteristics could be found. Q-band 1H-ENDOR spectroscopy on S2-state in solution and in crystal permitted the characterization of nearby protons coupled to the WOC, where the three largest couplings could be oriented within the crystal frame. With the aid of theoretical structure models of the WOC in its S2-state, an assignment of selected 1H hyperfine couplings to actual WOC ligating protons was postulated. Advisors/Committee Members: [email protected] (contact), w (gender), Prof. Dr. Robert Bittl (firstReferee), Prof. Dr. Holger Dau (furtherReferee).

Subjects/Keywords: EPR; ENDOR; photosystem II; PSII; Mn-Catalase; photosynthesis; WOC; water-oxidizing complex; 500 Naturwissenschaften und Mathematik::530 Physik

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APA (6th Edition):

Pudollek, S. (2012). Multifrequency EPR and ENDOR spectroscopy of the S2-state of the manganese complex in photosystem II. (Thesis). Freie Universität Berlin. Retrieved from http://dx.doi.org/10.17169/refubium-13149

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Pudollek, Susanne. “Multifrequency EPR and ENDOR spectroscopy of the S2-state of the manganese complex in photosystem II.” 2012. Thesis, Freie Universität Berlin. Accessed August 12, 2020. http://dx.doi.org/10.17169/refubium-13149.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Pudollek, Susanne. “Multifrequency EPR and ENDOR spectroscopy of the S2-state of the manganese complex in photosystem II.” 2012. Web. 12 Aug 2020.

Vancouver:

Pudollek S. Multifrequency EPR and ENDOR spectroscopy of the S2-state of the manganese complex in photosystem II. [Internet] [Thesis]. Freie Universität Berlin; 2012. [cited 2020 Aug 12]. Available from: http://dx.doi.org/10.17169/refubium-13149.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Pudollek S. Multifrequency EPR and ENDOR spectroscopy of the S2-state of the manganese complex in photosystem II. [Thesis]. Freie Universität Berlin; 2012. Available from: http://dx.doi.org/10.17169/refubium-13149

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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