Orbital-Tuning des Elektrondonators in Photosystem II: Eine kombinierte Photo-CIDNP-MAS-NMR- und Theorie-Untersuchung
Biophysik
Strukturbiologie
Theoretische Chemie: Elektronenstruktur, Dynamik, Simulation
Zusammenfassung der Projektergebnisse
In a combined experimental and theoretical approach, the structural origin of the unusual redox properties of the donor of photosystem II (PS2) has been targeted. The originally planned route to selectively 13C isotope label spinach, synechocystis and duckweed allowed to obtain one-dimensional 13C photo-CIDNP MAS NMR spectra. It was, however, not yet possible to increase the 13C label incorporation to an extend allowing for 13C-13C homonuclear correlation experiments. It appears that duckweed might provide the chance to reach higher levels but the adaptation of the plants to high 13C concentrations is rather time-consuming. In addition, a selective combination of labelling of cofactors and histidines would be the next step in confirming the involvement of protein environment in orbital tuning. These efforts are continued in our laboratory. With aminolevulinic acid (ALA) labelled duckweed samples having at 13C content of about 20% using one-dimensional spectroscopy, we were able to demonstrate (i) that photo-CIDNP can be observed directly in full plants without further purification, (ii) that chemical shifts from isolated D1D2 RC preparations are identical with those obtained from full plants, and (iii) that signals appear which do not originate from chlorophyll and pheophytin cofactors. In the meanwhile, using photosynthetic reaction centers (RCs) of Rhodobacter sphaeroides, the photo-CIDNP MAS NMR methodology has been evolved, allowing to operate with uniformly 15N labelled and modestly 13C labelled PS2 samples. In particular, heteronuclear correlation experiments (15N-1H, 13C-1H) as well as «spintorch» transfer experiments (NHHN, CHHC) are expected to provide structural details. Furthermore, shuttle-MAS NMR allows to obtain spectra from the millitesla range and therefore spectra which are mainly from the DR mechanism dominated which carry information of the triplet state and therefore the LUMO. On the theoretical-methodological side, we were able to perform important benchmarks concerning the frozen-density embedding method and the calculation of spin densities for chlorophyll-type radical cations. A major development achieved in this project was the development of the FDE-diab method, which allows to employ results of FDE-type calculations as a diabatic basis in subsequent calculations of adiabatic states, including their densities and spin densities. This method avoids both the overdelocalization problem of Kohn-Sham DFT as well as the overlocalization observed in FDE calculations, and hence facilitates robust and accurate calculations of spin densities for complex systems. Since it can be applied for arbitrary systems, it will be of practical use for purposes far beyond the original scope of this project. In the course of this project, the applicants hit some unexpected difficulties on the way to test the hinge model or possible alternatives both experimentally and theoretically. These methodical challenges have successfully been met during the project duration. It appears that the project now reached the state able to address the main question. Therefore, the two applicants plan to continue their collaboration and are going to apply for an extension of this project.
Projektbezogene Publikationen (Auswahl)
- Analysis of electron donors in photosystems in oxygenic photosynthesis by photo-CIDNP MAS NMR, J. Photochem. Photobiol. B 152 (2015) 261-271
M. Najdanova, G.J. Janssen, H.J.M. de Groot, J. Matysik, A. Alia
(Siehe online unter https://doi.org/10.1016/j.jphotobiol.2015.08.001) - Excitation Energies from Frozen- Density Embedding with Accurate Embedding Potentials, J. Chem. Phys. 142 (2015) 234101
D.G. Artiukhin, C. Jacob, J. Neugebauer
(Siehe online unter https://doi.org/10.1063/1.4922429) - Field-cycling NMR with high-resolution detection under magic-angle spinning: determination of field-window for nuclear hyperpolarization in a photosynthetic reaction center, Scientific Rep. 7 (2017) 12111
D. Gräsing, P. Bielytskyi, I.F. Céspedes-Camacho, A. Alia, T. Marquardsen, F. Engelke, J. Matysik
(Siehe online unter https://doi.org/10.1038/s41598-017-10413-y) - Photo-CIDNP in the Reaction center of the diatom cyclotella meneghiniana observed by 13C MAS NMR, Z. Phys. Chem. 231 (2017) 347-367
J.C. Zill, M. Kansy, R. Coss, L. Köhler, A. Alia, C. Wilhelm, J. Matysik
(Siehe online unter https://doi.org/10.1515/zpch-2016-0806) - Quantum Chemical Spin Densities for Radical Cations of Photosynthetic Pigment Models, Photochem. Photobiol. 93 (2017) 815-833
D.G. Artiukhin, C.J. Stein, M. Reiher, J. Neugebauer
(Siehe online unter https://doi.org/10.1111/php.12757) - 13C-1H transfer of light-induced hyperpolarization allows for selective detection of protons in frozen photosynthetic reaction center, J. Magn. Reson. 293 (2018) 82-91
P. Bielytskyi, D. Gräsing, K.R. Mote, K.B. Sai Sankar Gupta, S. Vega, P.K. Madhu, A. Alia, J. Matysik
(Siehe online unter https://doi.org/10.1016/j.jmr.2018.06.003) - Frozen-Density Embedding as a Quasi-Diabatization Tool: Charge-Localized States for Spin-Density Calculations, J. Chem. Phys. 149 (2018) 054103
D.G. Artiukhin, J. Neugebauer
(Siehe online unter https://doi.org/10.1063/1.5023290) - Photochemically induced dynamic nuclear polarization NMR on photosystem II: donor cofactor observed in entire plant, Scientific Rep. 8 (2018) 17853
G.J. Janssen, P. Bielytskyi, D.G. Artiukhin, J. Neugebauer, H.J.M. de Groot, J. Matysik, A. Alia
(Siehe online unter https://doi.org/10.1038/s41598-018-36074-z) - 15N-1H transfer of lightinduced nuclear hyperpolarization in frozen photosynthetic reaction centers, Appl. Magn. Reson. (2019)
P. Bielytskyi, D. Gräsing, S. Zahn, A. Alia, J. Matysik
(Siehe online unter https://doi.org/10.1007/s00723-019-1110-x) - Assignment of NMR resonances of protons covalently bound to photochemically active cofactors in photosynthetic reaction centers by 13C-1H photo-CIDNP MAS- J-HMQC experiment, J. Magn. Reson. 298 (2019) 64-76
P. Bielytskyi, D. Gräsing, S. Zahn, K.R. Mote, A. Alia, P.K. Madhu, J. Matysik
(Siehe online unter https://doi.org/10.1016/j.jmr.2018.11.013)
