Thema der Dissertation:
Experimental and Data Analytical Optimization of Time-Resolved Infrared Spectroscopy Provides Insight into the Mechanism of Photosynthetic Water Oxidation
Experimental and Data Analytical Optimization of Time-Resolved Infrared Spectroscopy Provides Insight into the Mechanism of Photosynthetic Water Oxidation
Abstract: Responsible for the oxygen content of the Earth's atmosphere, oxygenic photosynthesis is the key to the evolution of complex life on the planet. In the protein complex photosystem II (PSII) found in plants, algae and cyanobacteria, water molecules are split to release protons and electrons for use in the eventual production of chemical-energy storage compounds such as ATP, NADPH and, further downstream, sugars; molecular oxygen (O2) is released as a side-product. The reaction proceeds at a protein-bound metal-oxo cluster (Mn4CaOx), during a multi-photon absorption cycle in which the oxidation state of the cluster passes through so-called S-states. Infrared (IR) absorption spectroscopy can map S-state-induced electrostatic, chemical or structural changes through characteristic absorption bands assignable to amino acids and other molecular groups.
Here, two projects utilizing time-resolved Fourier-transform IR spectroscopy applied to PSII membrane particles from spinach will be presented. First, new analysis approaches to a step-scan data set provided the first clear evidence to the chemical nature of the critical and little understood reaction intermediates (termed the S′3 and S4 states) formed before O2 release. In concert with computational simulations, a detailed atomistic scheme of the S3→S0 transition is proposed. Second, the design, construction, and programming of a spectrometer to apply the rapid-scan FTIR method with a time resolution of <10 ms to the system is presented. Among other results, it was possible to record IR spectra, which show the temporal workings of processes associated with the electron transport chain on the acceptor side of PSII in a functioning system.
In conclusion, this work demonstrates that time-resolved FTIR spectroscopy is capable of providing new insights into the PSII catalytic cycle, but also that this requires a multitude of experimental, analytical and computational approaches.
Here, two projects utilizing time-resolved Fourier-transform IR spectroscopy applied to PSII membrane particles from spinach will be presented. First, new analysis approaches to a step-scan data set provided the first clear evidence to the chemical nature of the critical and little understood reaction intermediates (termed the S′3 and S4 states) formed before O2 release. In concert with computational simulations, a detailed atomistic scheme of the S3→S0 transition is proposed. Second, the design, construction, and programming of a spectrometer to apply the rapid-scan FTIR method with a time resolution of <10 ms to the system is presented. Among other results, it was possible to record IR spectra, which show the temporal workings of processes associated with the electron transport chain on the acceptor side of PSII in a functioning system.
In conclusion, this work demonstrates that time-resolved FTIR spectroscopy is capable of providing new insights into the PSII catalytic cycle, but also that this requires a multitude of experimental, analytical and computational approaches.
Time & Location
May 16, 2025 | 01:30 PM
Hörsaal B (0.1.01)
(Fachbereich Physik, Arnimallee 14, 14195 Berlin)