Prof. Dr. Athina Zouni
Profil
Forschungsthemen9
Basistechnologien-Forschertandem: Nutzung von Sonnenenergie für die Bioelektrokatalyse – Photobiohybride Elektroden für die lichtgetriebene Wertstoffsynthese (Phase II, TP B)
Quelle ↗Förderer: Bundesministerium für Forschung, Technologie und Raumfahrt Zeitraum: 02/2018 - 01/2021 Projektleitung: Prof. Dr. Athina Zouni
Cluster: Integrale Konzepte der Katalyse II(E3/D3) Die Aufdeckung des lichtgetriebenen Photosystem II-spezifischen Reparaturmechanismus: Kristallisation von Mn-freiem PSII und dessen strukturelle/funktionelle Analyse
Quelle ↗Förderer: DFG Exzellenzinitiative Cluster Zeitraum: 11/2012 - 10/2017 Projektleitung: Prof. Dr. Athina Zouni
Die Aufdeckung des photo-induzierten Assemblierungsmechanismus des lichtgetriebenen Wasseroxidationskomplexes in Photosystem II
Quelle ↗Förderer: DFG Exzellenzinitiative Cluster Zeitraum: 11/2017 - 12/2018 Projektleitung: Prof. Dr. Athina Zouni
EXC 314/1: Die Aufklärung des photo-induzierten Assemblierungsmechanismus, ausgehend von nativen und modifizierten Wasseroxidations-Katalysatoren des Photosystem II (AG Zouni) Biokatalytische Kopplung von Photosystem I mit FDH und CO-DH Superkomplexen
Quelle ↗Förderer: DFG Exzellenzstrategie Cluster Zeitraum: 01/2019 - 12/2022 Projektleitung: Prof. Dr. Athina Zouni
Momentaufnahmen der photosynthetischen Wasseroxidation: simultane Röntgenspektroskopie und Kristallografie
Quelle ↗Zeitraum: 11/2013 - 10/2016 Projektleitung: Prof. Dr. Athina Zouni
Momentaufnahmen der photosynthetischen Wasseroxidation: simultane Röntgenspektroskopie und Kristallografie
Quelle ↗Zeitraum: 11/2013 - 10/2017 Projektleitung: Prof. Dr. Athina Zouni
Nutzung von Sonnenenergie für die Biokatalyse – Entwicklung von Photo-Bioelektrodenstrukturen für die Synthese Isolation, Stabilisierung, Modifikation und Assemblierung von Photosystemen und Photosystemkomponenten in Hybrid-Assemblies zur Photobiokatalyse (Teilprojekt)
Quelle ↗Förderer: Bundesministerium für Forschung, Technologie und Raumfahrt Zeitraum: 08/2013 - 10/2017 Projektleitung: Prof. Dr. Athina Zouni
SFB 1078/1: Strukturelle Grundlagen der Protonenabgabe in der Wasser-Oxidation durch das Photosystem-II: Kristallisation, Röntgen- und Neutronenbeugungsanalyse von Chlorid-modifizierten und ortsgerichteten Varianten (TP A05)
Quelle ↗Förderer: DFG Sonderforschungsbereich Zeitraum: 01/2013 - 12/2020 Projektleitung: Prof. Dr. rer. nat. Holger Dobbek, Prof. Dr. Athina Zouni
SFB 1078/1: Strukturelle Grundlagen der Protonenabgabe in der Wasser-Oxidation durch das Photosystem II (TP A05)
Quelle ↗Förderer: DFG Sonderforschungsbereich Zeitraum: 01/2013 - 03/2021 Projektleitung: Prof. Dr. Athina Zouni, Prof. Dr. rer. nat. Holger Dobbek, Prof. i. R. Nikolaus Ernsting Ph. D., Prof. Dr. Dr. h. c. Peter Hegemann
Mögliche Industrie-Partner10
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BASF SE
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Publikationen25
Top 25 nach Zitationen — Quelle: OpenAlex (BAAI/bge-m3 embedded für Matching).
Nature · 1934 Zitationen · DOI
Nature · 1849 Zitationen · DOI
Nature Structural & Molecular Biology · 1163 Zitationen · DOI
Science · 797 Zitationen · DOI
The oxidation of water to dioxygen is catalyzed within photosystem II (PSII) by a Mn(4)Ca cluster, the structure of which remains elusive. Polarized extended x-ray absorption fine structure (EXAFS) measurements on PSII single crystals constrain the Mn(4)Ca cluster geometry to a set of three similar high-resolution structures. Combining polarized EXAFS and x-ray diffraction data, the cluster was placed within PSII, taking into account the overall trend of the electron density of the metal site and the putative ligands. The structure of the cluster from the present study is unlike either the 3.0 or 3.5 angstrom-resolution x-ray structures or other previously proposed models.
Proceedings of the National Academy of Sciences · 583 Zitationen · DOI
X-ray absorption spectroscopy was used to measure the damage caused by exposure to x-rays to the Mn(4)Ca active site in single crystals of photosystem II as a function of dose and energy of x-rays, temperature, and time. These studies reveal that the conditions used for structure determination by x-ray crystallography cause serious damage specifically to the metal-site structure. The x-ray absorption spectra show that the structure changes from one that is characteristic of a high-valent Mn(4)(III(2),IV(2)) oxo-bridged Mn(4)Ca cluster to that of Mn(II) in aqueous solution. This damage to the metal site occurs at a dose that is more than one order of magnitude lower than the dose that results in loss of diffractivity and is commonly considered safe for protein crystallography. These results establish quantitative x-ray dose parameters that are applicable to redox-active metalloproteins. This case study shows that a careful evaluation of the structural intactness of the active site(s) by spectroscopic techniques can validate structures derived from crystallography and that it can be a valuable complementary method before structure-function correlations of metalloproteins can be made on the basis of high-resolution x-ray crystal structures.
Nature · 519 Zitationen · DOI
Simultaneous Femtosecond X-ray Spectroscopy and Diffraction of Photosystem II at Room Temperature
2013Science · 430 Zitationen · DOI
Intense femtosecond x-ray pulses produced at the Linac Coherent Light Source (LCLS) were used for simultaneous x-ray diffraction (XRD) and x-ray emission spectroscopy (XES) of microcrystals of photosystem II (PS II) at room temperature. This method probes the overall protein structure and the electronic structure of the Mn4CaO5 cluster in the oxygen-evolving complex of PS II. XRD data are presented from both the dark state (S1) and the first illuminated state (S2) of PS II. Our simultaneous XRD-XES study shows that the PS II crystals are intact during our measurements at the LCLS, not only with respect to the structure of PS II, but also with regard to the electronic structure of the highly radiation-sensitive Mn4CaO5 cluster, opening new directions for future dynamics studies.
Nature · 386 Zitationen · DOI
Physical Chemistry Chemical Physics · 276 Zitationen · DOI
In the crystal structure of photosystem II (PSII) from the cyanobacterium <em>Thermosynechococcus elongatus</em> at 3.2 Å resolution, several loop regions of the principal protein subunits are now defined that were not interpretable previously at 3.8 Å resolution. The head groups and side chains of the organic cofactors of the electron transfer chain and of antenna chlorophyll <em>a</em> (Chl <em>a</em>) have been modeled, coordinating and hydrogen bonding amino acids identified and the nature of the binding pockets derived. The orientations of these cofactors resemble those of the reaction center from anoxygenic purple bacteria, but differences in hydrogen bonding and protein environment modulate their properties and provide the unique high redox potential (1.17 V) of the primary donor. Coordinating amino acids of manganese cluster, redox-active Tyr<sub>Z</sub> and non-haem Fe<sup>2+</sup> have been determined, and an all-<em>trans</em> β-carotene connects cytochrome <em>b</em>-559, Chl<sub>Z</sub> and primary electron donor (coordinates are available under PDB-code 1W5C).
Biochimica et Biophysica Acta (BBA) - Bioenergetics · 237 Zitationen · DOI
Proceedings of the National Academy of Sciences · 231 Zitationen · DOI
In oxygenic photosynthesis, light-driven oxidation of water to molecular oxygen is carried out by the oxygen-evolving complex (OEC) in photosystem II (PS II). Recently, we reported the room-temperature structures of PS II in the four (semi)stable S-states, S<sub>1</sub>, S<sub>2</sub>, S<sub>3</sub>, and S<sub>0</sub>, showing that a water molecule is inserted during the S<sub>2</sub> → S<sub>3</sub> transition, as a new bridging O(H)-ligand between Mn1 and Ca. To understand the sequence of events leading to the formation of this last stable intermediate state before O<sub>2</sub> formation, we recorded diffraction and Mn X-ray emission spectroscopy (XES) data at several time points during the S<sub>2</sub> → S<sub>3</sub> transition. At the electron acceptor site, changes due to the two-electron redox chemistry at the quinones, Q<sub>A</sub> and Q<sub>B</sub>, are observed. At the donor site, tyrosine Y<sub>Z</sub> and His190 H-bonded to it move by 50 µs after the second flash, and Glu189 moves away from Ca. This is followed by Mn1 and Mn4 moving apart, and the insertion of O<sub>X</sub>(H) at the open coordination site of Mn1. This water, possibly a ligand of Ca, could be supplied via a "water wheel"-like arrangement of five waters next to the OEC that is connected by a large channel to the bulk solvent. XES spectra show that Mn oxidation (τ of ∼350 µs) during the S<sub>2</sub> → S<sub>3</sub> transition mirrors the appearance of O<sub>X</sub> electron density. This indicates that the oxidation state change and the insertion of water as a bridging atom between Mn1 and Ca are highly correlated.
Nature Communications · 231 Zitationen · DOI
Drop-on-demand sample delivery for studying biocatalysts in action at X-ray free-electron lasers
2017Nature Methods · 201 Zitationen · DOI
Acta Crystallographica Section D Biological Crystallography · 190 Zitationen · DOI
An electrospun liquid microjet has been developed that delivers protein microcrystal suspensions at flow rates of 0.14-3.1 µl min(-1) to perform serial femtosecond crystallography (SFX) studies with X-ray lasers. Thermolysin microcrystals flowed at 0.17 µl min(-1) and diffracted to beyond 4 Å resolution, producing 14,000 indexable diffraction patterns, or four per second, from 140 µg of protein. Nanoflow electrospinning extends SFX to biological samples that necessitate minimal sample consumption.
Proceedings of the National Academy of Sciences · 166 Zitationen · DOI
Most of the dioxygen on earth is generated by the oxidation of water by photosystem II (PS II) using light from the sun. This light-driven, four-photon reaction is catalyzed by the Mn(4)CaO(5) cluster located at the lumenal side of PS II. Various X-ray studies have been carried out at cryogenic temperatures to understand the intermediate steps involved in the water oxidation mechanism. However, the necessity for collecting data at room temperature, especially for studying the transient steps during the O-O bond formation, requires the development of new methodologies. In this paper we report room temperature X-ray diffraction data of PS II microcrystals obtained using ultrashort (< 50 fs) 9 keV X-ray pulses from a hard X-ray free electron laser, namely the Linac Coherent Light Source. The results presented here demonstrate that the "probe before destroy" approach using an X-ray free electron laser works even for the highly-sensitive Mn(4)CaO(5) cluster in PS II at room temperature. We show that these data are comparable to those obtained in synchrotron radiation studies as seen by the similarities in the overall structure of the helices, the protein subunits and the location of the various cofactors. This work is, therefore, an important step toward future studies for resolving the structure of the Mn(4)CaO(5) cluster without any damage at room temperature, and of the reaction intermediates of PS II during O-O bond formation.
Biochimica et Biophysica Acta (BBA) - Bioenergetics · 164 Zitationen · DOI
Journal of Biological Chemistry · 161 Zitationen · DOI
The oxygen-evolving complex (OEC) in the membrane-bound protein complex photosystem II (PSII) catalyzes the water oxidation reaction that takes place in oxygenic photosynthetic organisms. We investigated the structural changes of the Mn4CaO5 cluster in the OEC during the S state transitions using x-ray absorption spectroscopy (XAS). Overall structural changes of the Mn4CaO5 cluster, based on the manganese ligand and Mn-Mn distances obtained from this study, were incorporated into the geometry of the Mn4CaO5 cluster in the OEC obtained from a polarized XAS model and the 1.9-Å high resolution crystal structure. Additionally, we compared the S1 state XAS of the dimeric and monomeric form of PSII from Thermosynechococcus elongatus and spinach PSII. Although the basic structures of the OEC are the same for T. elongatus PSII and spinach PSII, minor electronic structural differences that affect the manganese K-edge XAS between T. elongatus PSII and spinach PSII are found and may originate from differences in the second sphere ligand atom geometry.
Nature · 158 Zitationen · DOI
In natural photosynthesis, the light-driven splitting of water into electrons, protons and molecular oxygen forms the first step of the solar-to-chemical energy conversion process. The reaction takes place in photosystem II, where the Mn<sub>4</sub>CaO<sub>5</sub> cluster first stores four oxidizing equivalents, the S<sub>0</sub> to S<sub>4</sub> intermediate states in the Kok cycle, sequentially generated by photochemical charge separations in the reaction center and then catalyzes the O-O bond formation chemistry<sup>1-3</sup>. Here, we report room temperature snapshots by serial femtosecond X-ray crystallography to provide structural insights into the final reaction step of Kok's photosynthetic water oxidation cycle, the S<sub>3</sub>→[S<sub>4</sub>]→S<sub>0</sub> transition where O<sub>2</sub> is formed and Kok's water oxidation clock is reset. Our data reveal a complex sequence of events, which occur over micro- to milliseconds, comprising changes at the Mn<sub>4</sub>CaO<sub>5</sub> cluster, its ligands and water pathways as well as controlled proton release through the hydrogen-bonding network of the Cl1 channel. Importantly, the extra O atom O<sub>x</sub>, which was introduced as a bridging ligand between Ca and Mn1 during the S<sub>2</sub>→S<sub>3</sub> transition<sup>4-6</sup>, disappears or relocates in parallel with Y<sub>z</sub> reduction starting at approximately 700 μs after the third flash. The onset of O<sub>2</sub> evolution, as indicated by the shortening of the Mn1-Mn4 distance, occurs at around 1,200 μs, signifying the presence of a reduced intermediate, possibly a bound peroxide.
Nature Methods · 158 Zitationen · DOI
Biochimica et Biophysica Acta (BBA) - Bioenergetics · 145 Zitationen · DOI
Nature Communications · 143 Zitationen · DOI
Light-driven oxidation of water to molecular oxygen is catalyzed by the oxygen-evolving complex (OEC) in Photosystem II (PS II). This multi-electron, multi-proton catalysis requires the transport of two water molecules to and four protons from the OEC. A high-resolution 1.89 Å structure obtained by averaging all the S states and refining the data of various time points during the S<sub>2</sub> to S<sub>3</sub> transition has provided better visualization of the potential pathways for substrate water insertion and proton release. Our results indicate that the O1 channel is the likely water intake pathway, and the Cl1 channel is the likely proton release pathway based on the structural rearrangements of water molecules and amino acid side chains along these channels. In particular in the Cl1 channel, we suggest that residue D1-E65 serves as a gate for proton transport by minimizing the back reaction. The results show that the water oxidation reaction at the OEC is well coordinated with the amino acid side chains and the H-bonding network over the entire length of the channels, which is essential in shuttling substrate waters and protons.
Proceedings of the National Academy of Sciences · 137 Zitationen · DOI
The ultrabright femtosecond X-ray pulses provided by X-ray free-electron lasers open capabilities for studying the structure and dynamics of a wide variety of systems beyond what is possible with synchrotron sources. Recently, this "probe-before-destroy" approach has been demonstrated for atomic structure determination by serial X-ray diffraction of microcrystals. There has been the question whether a similar approach can be extended to probe the local electronic structure by X-ray spectroscopy. To address this, we have carried out femtosecond X-ray emission spectroscopy (XES) at the Linac Coherent Light Source using redox-active Mn complexes. XES probes the charge and spin states as well as the ligand environment, critical for understanding the functional role of redox-active metal sites. Kβ(1,3) XES spectra of Mn(II) and Mn(2)(III,IV) complexes at room temperature were collected using a wavelength dispersive spectrometer and femtosecond X-ray pulses with an individual dose of up to >100 MGy. The spectra were found in agreement with undamaged spectra collected at low dose using synchrotron radiation. Our results demonstrate that the intact electronic structure of redox active transition metal compounds in different oxidation states can be characterized with this shot-by-shot method. This opens the door for studying the chemical dynamics of metal catalytic sites by following reactions under functional conditions. The technique can be combined with X-ray diffraction to simultaneously obtain the geometric structure of the overall protein and the local chemistry of active metal sites and is expected to prove valuable for understanding the mechanism of important metalloproteins, such as photosystem II.
Proceedings of the National Academy of Sciences · 126 Zitationen · DOI
The heart of oxygenic photosynthesis is photosystem II (PSII), a multisubunit protein complex that uses solar energy to drive the splitting of water and production of molecular oxygen. The effectiveness of the photochemical reaction center of PSII depends on the efficient transfer of excitation energy from the surrounding antenna chlorophylls. A kinetic model for PSII, based on the x-ray crystal structure coordinates of 37 antenna and reaction center pigment molecules, allows us to map the major energy transfer routes from the antenna chlorophylls to the reaction center chromophores. The model shows that energy transfer to the reaction center is slow compared with the rate of primary electron transport and depends on a few bridging chlorophyll molecules. This unexpected energetic isolation of the reaction center in PSII is similar to that found in the bacterial photosystem, conflicts with the established view of the photophysics of PSII, and may be a functional requirement for primary photochemistry in photosynthesis. In addition, the model predicts a value for the intrinsic photochemical rate constant that is 4 times that found in bacterial reaction centers.
Structure · 125 Zitationen · DOI
Nature Methods · 124 Zitationen · DOI
Kooperationen11
Bestätigte Forscher↔Partner-Paare aus HU-FIS — Gold-Standard-Positive für das Matching.
EXC 314/1: Die Aufklärung des photo-induzierten Assemblierungsmechanismus, ausgehend von nativen und modifizierten Wasseroxidations-Katalysatoren des Photosystem II (AG Zouni) Biokatalytische Kopplung von Photosystem I mit FDH und CO-DH Superkomplexen
university
EXC 314/1: Die Aufklärung des photo-induzierten Assemblierungsmechanismus, ausgehend von nativen und modifizierten Wasseroxidations-Katalysatoren des Photosystem II (AG Zouni) Biokatalytische Kopplung von Photosystem I mit FDH und CO-DH Superkomplexen
university
EXC 314/1: Die Aufklärung des photo-induzierten Assemblierungsmechanismus, ausgehend von nativen und modifizierten Wasseroxidations-Katalysatoren des Photosystem II (AG Zouni) Biokatalytische Kopplung von Photosystem I mit FDH und CO-DH Superkomplexen
other
EXC 314/1: Die Aufklärung des photo-induzierten Assemblierungsmechanismus, ausgehend von nativen und modifizierten Wasseroxidations-Katalysatoren des Photosystem II (AG Zouni) Biokatalytische Kopplung von Photosystem I mit FDH und CO-DH Superkomplexen
other
SFB 1078/1: Strukturelle Grundlagen der Protonenabgabe in der Wasser-Oxidation durch das Photosystem II (TP A05)
university
EXC 314/1: Die Aufklärung des photo-induzierten Assemblierungsmechanismus, ausgehend von nativen und modifizierten Wasseroxidations-Katalysatoren des Photosystem II (AG Zouni) Biokatalytische Kopplung von Photosystem I mit FDH und CO-DH Superkomplexen
other
Momentaufnahmen der photosynthetischen Wasseroxidation: simultane Röntgenspektroskopie und Kristallografie
university
EXC 314/1: Die Aufklärung des photo-induzierten Assemblierungsmechanismus, ausgehend von nativen und modifizierten Wasseroxidations-Katalysatoren des Photosystem II (AG Zouni) Biokatalytische Kopplung von Photosystem I mit FDH und CO-DH Superkomplexen
other
Basistechnologien-Forschertandem: Nutzung von Sonnenenergie für die Bioelektrokatalyse – Photobiohybride Elektroden für die lichtgetriebene Wertstoffsynthese (Phase II, TP B)
other
EXC 314/1: Die Aufklärung des photo-induzierten Assemblierungsmechanismus, ausgehend von nativen und modifizierten Wasseroxidations-Katalysatoren des Photosystem II (AG Zouni) Biokatalytische Kopplung von Photosystem I mit FDH und CO-DH Superkomplexen
university
EXC 314/1: Die Aufklärung des photo-induzierten Assemblierungsmechanismus, ausgehend von nativen und modifizierten Wasseroxidations-Katalysatoren des Photosystem II (AG Zouni) Biokatalytische Kopplung von Photosystem I mit FDH und CO-DH Superkomplexen
university
Stammdaten
Identität, Organisation und Kontakt aus HU-FIS.
- Name
- Prof. Dr. Athina Zouni
- Titel
- Prof. Dr.
- Fakultät
- Lebenswissenschaftliche Fakultät
- Institut
- Institut für Biologie
- Telefon
- +49 30 2093-47930
- HU-FIS-Profil
- Quelle ↗
- Zuletzt gescrapt
- 26.4.2026, 01:14:36