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Artiukhin DG, Eschenbach P, Matysik J, Neugebauer J. Theoretical Assessment of Hinge-Type Models for Electron Donors in Reaction Centers of Photosystems I and II as well as of Purple Bacteria. J Phys Chem B 2021; 125:3066-3079. [PMID: 33749260 DOI: 10.1021/acs.jpcb.0c10656] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Hinge-type molecular models for electron donors in reaction centers of Photosystems I and II and purple bacteria were investigated using a two-state computational approach based on frozen-density embedding (FDE). This methodology, dubbed FDE-diab, is known to avoid consequences of the self-interaction error as far as intermolecular phenomena are concerned, which allows a prediction of qualitatively correct spin densities for large biomolecular systems. The calculated spin density distributions are in a good agreement with available experimental results and demonstrated a very high sensitivity to changes in the relative orientation of cofactors and amino acid protonation states. This allows a validation of the previously proposed hinge-type models providing hints on possible protonation states of axial histidine molecules.
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Affiliation(s)
- Denis G Artiukhin
- Department of Chemistry, Aarhus Universitet, DK-8000 Aarhus, Denmark
| | - Patrick Eschenbach
- Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Simulation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
| | - Jörg Matysik
- Institut für Analytische Chemie, Universität Leipzig, Linnéstr. 3, 04103 Leipzig, Germany
| | - Johannes Neugebauer
- Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Simulation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
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2
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Ding Y, Kiryutin AS, Zhao Z, Xu QZ, Zhao KH, Kurle P, Bannister S, Kottke T, Sagdeev RZ, Ivanov KL, Yurkovskaya AV, Matysik J. Tailored flavoproteins acting as light-driven spin machines pump nuclear hyperpolarization. Sci Rep 2020; 10:18658. [PMID: 33122681 PMCID: PMC7596710 DOI: 10.1038/s41598-020-75627-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Accepted: 10/15/2020] [Indexed: 11/24/2022] Open
Abstract
The solid-state photo-chemically induced dynamic nuclear polarization (photo-CIDNP) effect generates non-Boltzmann nuclear spin magnetization, referred to as hyperpolarization, allowing for high gain of sensitivity in nuclear magnetic resonance (NMR). Well known to occur in photosynthetic reaction centers, the effect was also observed in a light-oxygen-voltage (LOV) domain of the blue-light receptor phototropin, in which the functional cysteine was removed to prevent photo-chemical reactions with the cofactor, a flavin mononucleotide (FMN). Upon illumination, the FMN abstracts an electron from a tryptophan to form a transient spin-correlated radical pair (SCRP) generating the photo-CIDNP effect. Here, we report on designed molecular spin-machines producing nuclear hyperpolarization upon illumination: a LOV domain of aureochrome1a from Phaeodactylum tricornutum, and a LOV domain named 4511 from Methylobacterium radiotolerans (Mr4511) which lacks an otherwise conserved tryptophan in its wild-type form. Insertion of the tryptophan at canonical and novel positions in Mr4511 yields photo-CIDNP effects observed by 15N and 1H liquid-state high-resolution NMR with a characteristic magnetic-field dependence indicating an involvement of anisotropic magnetic interactions and a slow-motion regime in the transient paramagnetic state. The heuristic biomimetic design opens new categories of experiments to analyze and apply the photo-CIDNP effect.
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Affiliation(s)
- Yonghong Ding
- Institut für Analytische Chemie, Universität Leipzig, Linnéstr. 3, 04103, Leipzig, Germany
| | - Alexey S Kiryutin
- International Tomography Center, Siberian Branch of Russian Academy of Sciences, Institutskaya, 3a, Novosibirsk, 630090, Russia
- Novosibirsk State University, Pirogova 1, Novosibirsk, 630090, Russia
| | - Ziyue Zhao
- Institut für Analytische Chemie, Universität Leipzig, Linnéstr. 3, 04103, Leipzig, Germany
| | - Qian-Zhao Xu
- Institut für Analytische Chemie, Universität Leipzig, Linnéstr. 3, 04103, Leipzig, Germany
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Kai-Hong Zhao
- State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China
| | - Patrick Kurle
- Institut für Analytische Chemie, Universität Leipzig, Linnéstr. 3, 04103, Leipzig, Germany
| | - Saskia Bannister
- Physikalische und Biophysikalische Chemie, Universität Bielefeld, Universitätsstr. 25, 33615, Bielefeld, Germany
| | - Tilman Kottke
- Physikalische und Biophysikalische Chemie, Universität Bielefeld, Universitätsstr. 25, 33615, Bielefeld, Germany
| | - Renad Z Sagdeev
- International Tomography Center, Siberian Branch of Russian Academy of Sciences, Institutskaya, 3a, Novosibirsk, 630090, Russia
- Novosibirsk State University, Pirogova 1, Novosibirsk, 630090, Russia
| | - Konstantin L Ivanov
- International Tomography Center, Siberian Branch of Russian Academy of Sciences, Institutskaya, 3a, Novosibirsk, 630090, Russia
- Novosibirsk State University, Pirogova 1, Novosibirsk, 630090, Russia
| | - Alexandra V Yurkovskaya
- International Tomography Center, Siberian Branch of Russian Academy of Sciences, Institutskaya, 3a, Novosibirsk, 630090, Russia
- Novosibirsk State University, Pirogova 1, Novosibirsk, 630090, Russia
| | - Jörg Matysik
- Institut für Analytische Chemie, Universität Leipzig, Linnéstr. 3, 04103, Leipzig, Germany.
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Artiukhin DG, Eschenbach P, Neugebauer J. Computational Investigation of the Spin-Density Asymmetry in Photosynthetic Reaction Center Models from First Principles. J Phys Chem B 2020; 124:4873-4888. [DOI: 10.1021/acs.jpcb.0c02827] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
| | - Patrick Eschenbach
- Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Simulation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
| | - Johannes Neugebauer
- Theoretische Organische Chemie, Organisch-Chemisches Institut and Center for Multiscale Theory and Simulation, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
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Zill JC, Kansy M, Goss R, Alia A, Wilhelm C, Matysik J. 15N photo-CIDNP MAS NMR on both photosystems and magnetic field-dependent 13C photo-CIDNP MAS NMR in photosystem II of the diatom Phaeodactylum tricornutum. PHOTOSYNTHESIS RESEARCH 2019; 140:151-171. [PMID: 30194671 DOI: 10.1007/s11120-018-0578-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Accepted: 08/24/2018] [Indexed: 05/14/2023]
Abstract
Diatoms contribute about 20-25% to the global marine productivity and are successful autotrophic players in all aquatic ecosystems, which raises the question whether this performance is caused by differences in their photosynthetic apparatus. Photo-CIDNP MAS NMR presents a unique tool to obtain insights into the reaction centres of photosystems (PS), by selective enhancement of NMR signals from both, the electron donor and the primary electron acceptor molecules. Here, we present the first observation of the solid-state photo-CIDNP effect in the pennate diatoms. In comparison to plant PSs, similar spectral patterns have been observed for PS I at 9.4 T and PS II at 4.7 T in the PSs of Phaeodactylum tricornutum. Studies at different magnetic fields reveal a surprising sign change of the 13C photo-CIDNP MAS NMR signals indicating an alternative arrangement of cofactors which allows to quench the Chl a donor triplet state in contrast to the situation in plant PS II. This unusual quenching mechanism is related to a carotenoid molecule in close vicinity to the Chl a donor. In addition to the photo-CIDNP MAS NMR signals arising from the donor and the primary electron acceptor cofactors, a complete set of signals of the imidazole ring ligating to the magnesium of Chl a can be observed.
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Affiliation(s)
- Jeremias C Zill
- Institute of Analytical Chemistry, University of Leipzig, Johannisallee 29, 04103, Leipzig, Germany
| | - Marcel Kansy
- Institute of Biology, University of Leipzig, Johannisallee 21-23, 04103, Leipzig, Germany
| | - Reimund Goss
- Institute of Biology, University of Leipzig, Johannisallee 21-23, 04103, Leipzig, Germany
| | - A Alia
- Leiden Institute of Chemistry, University of Leiden, Einsteinweg 55, P.O. Box 9502, 2300 RA, Leiden, The Netherlands
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04107, Leipzig, Germany
| | - Christian Wilhelm
- Institute of Biology, University of Leipzig, Johannisallee 21-23, 04103, Leipzig, Germany
| | - Jörg Matysik
- Institute of Analytical Chemistry, University of Leipzig, Johannisallee 29, 04103, Leipzig, Germany.
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Janssen GJ, Bielytskyi P, Artiukhin DG, Neugebauer J, de Groot HJM, Matysik J, Alia A. Photochemically induced dynamic nuclear polarization NMR on photosystem II: donor cofactor observed in entire plant. Sci Rep 2018; 8:17853. [PMID: 30552342 PMCID: PMC6294776 DOI: 10.1038/s41598-018-36074-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2018] [Accepted: 11/13/2018] [Indexed: 12/18/2022] Open
Abstract
The solid-state photo-CIDNP (photochemically induced dynamic nuclear polarization) effect allows for increase of signal and sensitivity in magic-angle spinning (MAS) NMR experiments. The effect occurs in photosynthetic reaction centers (RC) proteins upon illumination and induction of cyclic electron transfer. Here we show that the strength of the effect allows for observation of the cofactors forming the spin-correlated radical pair (SCRP) in isolated proteins, in natural photosynthetic membranes as well as in entire plants. To this end, we measured entire selectively 13C isotope enriched duckweed plants (Spirodela oligorrhiza) directly in the MAS rotor. Comparison of 13C photo-CIDNP MAS NMR spectra of photosystem II (PS2) obtained from different levels of RC isolation, from entire plant to isolated RC complex, demonstrates the intactness of the photochemical machinery upon isolation. The SCRP in PS2 is structurally and functionally very similar in duckweed and spinach (Spinacia oleracea). The analysis of the photo-CIDNP MAS NMR spectra reveals a monomeric Chl a donor. There is an experimental evidence for matrix involvement, most likely due to the axial donor histidine, in the formation of the SCRP. Data do not suggest a chemical modification of C-131 carbonyl position of the donor cofactor.
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Affiliation(s)
- Geertje J Janssen
- University of Leiden, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA, Leiden, The Netherlands
| | - Pavlo Bielytskyi
- Universität Leipzig, Institute of Analytical Chemistry, Johannisallee 29, D-04103, Leipzig, Germany
| | - Denis G Artiukhin
- Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut and Center for Multiscale Theory and Computation, Corrensstraße 40, D-48149, Münster, Germany
| | - Johannes Neugebauer
- Westfälische Wilhelms-Universität Münster, Organisch-Chemisches Institut and Center for Multiscale Theory and Computation, Corrensstraße 40, D-48149, Münster, Germany
| | - Huub J M de Groot
- University of Leiden, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA, Leiden, The Netherlands
| | - Jörg Matysik
- Universität Leipzig, Institute of Analytical Chemistry, Johannisallee 29, D-04103, Leipzig, Germany.
| | - A Alia
- University of Leiden, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA, Leiden, The Netherlands.
- Universität Leipzig, Institute of Medical Physics and Biophysics, Härtelstr. 16-18, D-04107, Leipzig, Germany.
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Bielytskyi P, Gräsing D, Mote KR, Sai Sankar Gupta KB, Vega S, Madhu PK, Alia A, Matysik J. 13C → 1H transfer of light-induced hyperpolarization allows for selective detection of protons in frozen photosynthetic reaction center. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2018; 293:82-91. [PMID: 29909081 DOI: 10.1016/j.jmr.2018.06.003] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2018] [Revised: 06/06/2018] [Accepted: 06/07/2018] [Indexed: 05/14/2023]
Abstract
In the present study, we exploit the light-induced hyperpolarization occurring on 13C nuclei due to the solid-state photochemically induced dynamic nuclear polarization (photo-CIDNP) effect to boost the NMR signal intensity of selected protons via inverse cross-polarization. Such hyperpolarization transfer is implemented into 1H-detected two-dimensional 13C-1H correlation magic-angle-spinning (MAS) NMR experiment to study protons in frozen photosynthetic reaction centers (RCs). As a first trial, the performance of such an experiment is tested on selectively 13C labeled RCs from the purple bacteria of Rhodobacter sphaeroides. We observed response from the protons belonging to the photochemically active cofactors in their native protein environment. Such an approach is a potential heteronuclear spin-torch experiment which could be complementary to the classical heteronuclear correlation (HETCOR) experiments for mapping proton chemical shifts of photosynthetic cofactors and to understand the role of the proton pool around the electron donors in the electron transfer process occurring during photosynthesis.
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Affiliation(s)
- Pavlo Bielytskyi
- Institut für Analytische Chemie, Universität Leipzig, Linnéstraße 3, D-04103 Leipzig, Germany
| | - Daniel Gräsing
- Institut für Analytische Chemie, Universität Leipzig, Linnéstraße 3, D-04103 Leipzig, Germany
| | - Kaustubh R Mote
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, 36/P Gopanpally Village, Serilingampally Mandal, Ranga Reddy District, Hyderabad 500107, India
| | | | - Shimon Vega
- Department of Chemical Physics, Weizmann Institute of Science, 76100 Rechovot, Israel
| | - P K Madhu
- TIFR Centre for Interdisciplinary Sciences, Tata Institute of Fundamental Research, 36/P Gopanpally Village, Serilingampally Mandal, Ranga Reddy District, Hyderabad 500107, India; Department of Chemical Sciences, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India
| | - A Alia
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2301 RA Leiden, The Netherlands; Institut für Medizinische Physik und Biophysik, Universität Leipzig, Härtelstr. 16-18, D-04107 Leipzig, Germany
| | - Jörg Matysik
- Institut für Analytische Chemie, Universität Leipzig, Linnéstraße 3, D-04103 Leipzig, Germany.
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Zill JC, He Z, Tank M, Ferlez BH, Canniffe DP, Lahav Y, Bellstedt P, Alia A, Schapiro I, Golbeck JH, Bryant DA, Matysik J. 15N photo-CIDNP MAS NMR analysis of reaction centers of Chloracidobacterium thermophilum. PHOTOSYNTHESIS RESEARCH 2018; 137:295-305. [PMID: 29603082 DOI: 10.1007/s11120-018-0504-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Accepted: 03/23/2018] [Indexed: 06/08/2023]
Abstract
Photochemically induced dynamic nuclear polarization (photo-CIDNP) has been observed in the homodimeric, type-1 photochemical reaction centers (RCs) of the acidobacterium, Chloracidobacterium (Cab.) thermophilum, by 15N magic-angle spinning (MAS) solid-state NMR under continuous white-light illumination. Three light-induced emissive (negative) signals are detected. In the RCs of Cab. thermophilum, three types of (bacterio)chlorophylls have previously been identified: bacteriochlorophyll a (BChl a), chlorophyll a (Chl a), and Zn-bacteriochlorophyll a' (Zn-BChl a') (Tsukatani et al. in J Biol Chem 287:5720-5732, 2012). Based upon experimental and quantum chemical 15N NMR data, we assign the observed signals to a Chl a cofactor. We exclude Zn-BChl because of its measured spectroscopic properties. We conclude that Chl a is the primary electron acceptor, which implies that the primary donor is most likely Zn-BChl a'. Chl a and 81-OH Chl a have been shown to be the primary electron acceptors in green sulfur bacteria and heliobacteria, respectively, and thus a Chl a molecule serves this role in all known homodimeric type-1 RCs.
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Affiliation(s)
- Jeremias C Zill
- Institute of Analytical Chemistry, University of Leipzig, Johannisallee 29, 04103, Leipzig, Germany
| | - Zhihui He
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Marcus Tank
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA
- Department of Biological Sciences, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji-shi, Tokyo, 192-0397, Japan
| | - Bryan H Ferlez
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Daniel P Canniffe
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Yigal Lahav
- Fritz Haber Center of Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, 91904, Jerusalem, Israel
- Migal-Galilee Research Institute, S. Industrial Zone, 12100, Kiryat Shmona, Israel
| | - Peter Bellstedt
- Institute of Organic and Macromolecular Chemistry, Friedrich-Schiller-Universität Jena, Humboldtstraße 10, 07743, Jena, Germany
| | - A Alia
- Institute of Analytical Chemistry, University of Leipzig, Johannisallee 29, 04103, Leipzig, Germany
- Leiden Institute of Chemistry, University of Leiden, Einsteinweg 55, P.O. Box 9502, 2300 RA, Leiden, The Netherlands
- Institute of Medical Physics and Biophysics, University of Leipzig, Härtelstr. 16-18, 04107, Leipzig, Germany
| | - Igor Schapiro
- Fritz Haber Center of Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem, 91904, Jerusalem, Israel
| | - John H Golbeck
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA
- Department of Chemistry, The Pennsylvania State University, University Park, PA, 16802, USA
| | - Donald A Bryant
- Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, PA, 16802, USA
- Department of Chemistry and Biochemistry, Montana State University, Bozeman, MT, 59717, USA
| | - Jörg Matysik
- Institute of Analytical Chemistry, University of Leipzig, Johannisallee 29, 04103, Leipzig, Germany.
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Zill JC, Kansy M, Goss R, Köhler L, Alia A, Wilhelm C, Matysik J. Photo-CIDNP in the Reaction Center of the Diatom Cyclotella meneghiniana Observed by 13C MAS NMR. Z PHYS CHEM 2016. [DOI: 10.1515/zpch-2016-0806] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Abstract
Photo-CIDNP MAS NMR presents a unique tool to obtain insight into the photosynthetic reaction centers (RCs) of bacteria and plants. Using the dramatic enhancement of sensitivity and selectivity of the solid-state photo-CIDNP effect, structural as well as functional information can be obtained from the cofactor molecules forming a light-induced spin-correlated radical pair (SCRP) in a given reaction center. Here we demonstrate that the effect can be observed in a further species, which belongs neither to the plant nor the bacteria kingdom. Cyclotella (C.) meneghiniana is a member of the diatom phylum and, therefore, belongs to the kingdom of chromista. Chromista are some of the most productive organisms in nature, even in comparison to trees and terrestrial grasses. The observation of the effect in chromista indicates that the effect occurs in all photosynthetic organisms and completes the list with the last phototrophic kingdoms. Our data also demonstrate that the photo- and spin-chemical machineries of photosystem I of plants and chromista are very similar with respect to structure as well as function.
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Affiliation(s)
- Jeremias C. Zill
- University of Leipzig, Institute of Analytical Chemistry, Johannisallee 29, D-04103 Leipzig, Germany
| | - Marcel Kansy
- University of Leipzig, Institute of Biology, Abteilung Pflanzenphysiologie, Johannisallee 21-23, D-04103 Leipzig, Germany
| | - Reimund Goss
- University of Leipzig, Institute of Biology, Abteilung Pflanzenphysiologie, Johannisallee 21-23, D-04103 Leipzig, Germany
| | - Lisa Köhler
- University of Leipzig, Institute of Analytical Chemistry, Johannisallee 29, D-04103 Leipzig, Germany
| | - A. Alia
- University of Leiden, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
- University of Leipzig, Institute of Medical Physics and Biophysics, Härtelstr. 16-18, D-04107 Leipzig, Germany
| | - Christian Wilhelm
- University of Leipzig, Institute of Biology, Abteilung Pflanzenphysiologie, Johannisallee 21-23, D-04103 Leipzig, Germany
| | - Jörg Matysik
- University of Leipzig, Institute of Analytical Chemistry, Johannisallee 29, D-04103 Leipzig, Germany
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Sosnovsky DV, Jeschke G, Matysik J, Vieth HM, Ivanov KL. Level crossing analysis of chemically induced dynamic nuclear polarization: Towards a common description of liquid-state and solid-state cases. J Chem Phys 2016; 144:144202. [DOI: 10.1063/1.4945341] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Denis V. Sosnovsky
- International Tomography Centre of SB RAS, Institutskaya 3a, 630090, Novosibirsk, Russia
- Novosibirsk State University, Pirogova 2, 630090, Novosibirsk, Russia
| | - Gunnar Jeschke
- Institut für Physikalische Chemie, ETH Zürich, Vladimir-Prelog-Weg 2, CH-8093 Zürich, Switzerland
| | - Jörg Matysik
- Institut für Analytische Chemie, Universität Leipzig, Linnéstr. 3, D-04103 Leipzig, Germany
| | - Hans-Martin Vieth
- International Tomography Centre of SB RAS, Institutskaya 3a, 630090, Novosibirsk, Russia
- Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, D-14195 Berlin, Germany
| | - Konstantin L. Ivanov
- International Tomography Centre of SB RAS, Institutskaya 3a, 630090, Novosibirsk, Russia
- Novosibirsk State University, Pirogova 2, 630090, Novosibirsk, Russia
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10
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Najdanova M, Janssen GJ, de Groot HJM, Matysik J, Alia A. Analysis of electron donors in photosystems in oxygenic photosynthesis by photo-CIDNP MAS NMR. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY 2015; 152:261-71. [PMID: 26282679 DOI: 10.1016/j.jphotobiol.2015.08.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 08/04/2015] [Accepted: 08/05/2015] [Indexed: 10/23/2022]
Abstract
Both photosystem I and photosystem II are considerably similar in molecular architecture but they operate at very different electrochemical potentials. The origin of the different redox properties of these RCs is not yet clear. In recent years, insight was gained into the electronic structure of photosynthetic cofactors through the application of photochemically induced dynamic nuclear polarization (photo-CIDNP) with magic-angle spinning NMR (MAS NMR). Non-Boltzmann populated nuclear spin states of the radical pair lead to strongly enhanced signal intensities that allow one to observe the solid-state photo-CIDNP effect from both photosystem I and II from isolated reaction center of spinach (Spinacia oleracea) and duckweed (Spirodela oligorrhiza) and from the intact cells of the cyanobacterium Synechocystis by (13)C and (15)N MAS NMR. This review provides an overview on the photo-CIDNP MAS NMR studies performed on PSI and PSII that provide important ingredients toward reconstruction of the electronic structures of the donors in PSI and PSII.
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Affiliation(s)
- M Najdanova
- University of Leipzig, Institute of Analytical Chemistry, Johannisallee 29, D-04103 Leipzig, Germany
| | - G J Janssen
- University of Leiden, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - H J M de Groot
- University of Leiden, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - J Matysik
- University of Leipzig, Institute of Analytical Chemistry, Johannisallee 29, D-04103 Leipzig, Germany
| | - A Alia
- University of Leiden, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands; University of Leipzig, Institute of Medical Physics and Biophysics, Härtelstr. 16-18, D-04107 Leipzig, Germany.
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11
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Janssen GJ, Roy E, Matysik J, Alia A. N Photo-CIDNP MAS NMR To Reveal Functional Heterogeneity in Electron Donor of Different Plant Organisms. APPLIED MAGNETIC RESONANCE 2012; 42:57-67. [PMID: 22303078 PMCID: PMC3260425 DOI: 10.1007/s00723-011-0283-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2011] [Revised: 08/31/2011] [Indexed: 05/27/2023]
Abstract
In plants and cyanobacteria, two light-driven electron pumps, photosystems I and II (PSI, PSII), facilitate electron transfer from water to carbon dioxide with quantum efficiency close to unity. While similar in structure and function, the reaction centers of PSI and PSII operate at widely different potentials with PSI being the strongest reducing agent known in living nature. Photochemically induced dynamic nuclear polarization (photo-CIDNP) in magic-angle spinning (MAS) nuclear magnetic resonance (NMR) measurements provides direct excess to the heart of large photosynthetic complexes (A. Diller, Alia, E. Roy, P. Gast, H.J. van Gorkom, J. Zaanen, H.J.M. de Groot, C. Glaubitz, J. Matysik, Photosynth. Res. 84, 303-308, 2005; Alia, E. Roy, P. Gast, H.J. van Gorkom, H.J.M. de Groot, G. Jeschke, J. Matysik, J. Am. Chem. Soc. 126, 12819-12826, 2004). By combining the dramatic signal increase obtained from the solid-state photo-CIDNP effect with (15)N isotope labeling of PSI, we were able to map the electron spin density in the active cofactors of PSI and study primary charge separation at atomic level. We compare data obtained from two different PSI proteins, one from spinach (Spinacia oleracea) and other from the aquatic plant duckweed (Spirodella oligorrhiza). Results demonstrate a large flexibility of the PSI in terms of its electronic architecture while their electronic ground states are strictly conserved.
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Affiliation(s)
- Geertje J. Janssen
- Leiden Institute of Chemistry, Leiden University, P.O. box 9502, 2300 RA Leiden, The Netherlands
| | - Esha Roy
- Leiden Institute of Chemistry, Leiden University, P.O. box 9502, 2300 RA Leiden, The Netherlands
| | - Jörg Matysik
- Leiden Institute of Chemistry, Leiden University, P.O. box 9502, 2300 RA Leiden, The Netherlands
| | - A. Alia
- Leiden Institute of Chemistry, Leiden University, P.O. box 9502, 2300 RA Leiden, The Netherlands
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12
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Janssen GJ, Daviso E, van Son M, de Groot HJM, Alia A, Matysik J. Observation of the solid-state photo-CIDNP effect in entire cells of cyanobacteria Synechocystis. PHOTOSYNTHESIS RESEARCH 2010; 104:275-82. [PMID: 20094793 PMCID: PMC2882559 DOI: 10.1007/s11120-009-9508-1] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/09/2009] [Accepted: 11/25/2009] [Indexed: 05/18/2023]
Abstract
Cyanobacteria are widely used as model organism of oxygenic photosynthesis due to being the simplest photosynthetic organisms containing both photosystem I and II (PSI and PSII). Photochemically induced dynamic nuclear polarization (photo-CIDNP) (13)C magic-angle spinning (MAS) NMR is a powerful tool in understanding the photosynthesis machinery down to atomic level. Combined with selective isotope enrichment this technique has now opened the door to study primary charge separation in whole living cells. Here, we present the first photo-CIDNP observed in whole cells of the cyanobacterium Synechocystis.
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Affiliation(s)
- Geertje J. Janssen
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Eugenio Daviso
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Martin van Son
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Huub J. M. de Groot
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - A. Alia
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Jörg Matysik
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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13
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Matysik J, Diller A, Roy E, Alia A. The solid-state photo-CIDNP effect. PHOTOSYNTHESIS RESEARCH 2009; 102:427-35. [PMID: 19238579 PMCID: PMC2777203 DOI: 10.1007/s11120-009-9403-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Accepted: 01/12/2009] [Indexed: 05/05/2023]
Abstract
The solid-state photo-CIDNP effect is the occurrence of a non-Boltzmann nuclear spin polarization in rigid samples upon illumination. For solid-state NMR, which can detect this enhanced nuclear polarization as a strong modification of signal intensity, the effect allows for new classes of experiments. Currently, the photo- and spin-chemical machinery of various RCs is studied by photo-CIDNP MAS NMR in detail. Until now, the effect has only been observed at high magnetic fields with (13)C and (15)N MAS NMR and in natural photosynthetic RC preparations in which blocking of the acceptor leads to cyclic electron transfer. In terms of irreversible thermodynamics, the high-order spin structure of the initial radical pair can be considered as a transient order phenomenon emerging under non-equilibrium conditions and as a first manifestation of order in the photosynthetic process. The solid-state photo- CIDNP effect appears to be an intrinsic property of natural RCs. The conditions of its occurrence seem to be conserved in evolution. The effect may be based on the same fundamental principles as the highly optimized electron transfer. Hence, the effect may allow for guiding artificial photosynthesis.
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Affiliation(s)
- Jörg Matysik
- Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
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14
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Roy E, Rohmer T, Gast P, Jeschke G, Alia A, Matysik J. Characterization of the Primary Radical Pair in Reaction Centers of Heliobacillus mobilis by 13C Photo-CIDNP MAS NMR. Biochemistry 2008; 47:4629-35. [DOI: 10.1021/bi800030g] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Esha Roy
- Leiden Institute of Chemistry, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Leiden Institute of Physics, P.O. box 9504, 2300 RA Leiden, The Netherlands, and Physikalische Chemie, Universität Konstanz, 78457 Konstanz, Germany
| | - Thierry Rohmer
- Leiden Institute of Chemistry, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Leiden Institute of Physics, P.O. box 9504, 2300 RA Leiden, The Netherlands, and Physikalische Chemie, Universität Konstanz, 78457 Konstanz, Germany
| | - Peter Gast
- Leiden Institute of Chemistry, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Leiden Institute of Physics, P.O. box 9504, 2300 RA Leiden, The Netherlands, and Physikalische Chemie, Universität Konstanz, 78457 Konstanz, Germany
| | - Gunnar Jeschke
- Leiden Institute of Chemistry, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Leiden Institute of Physics, P.O. box 9504, 2300 RA Leiden, The Netherlands, and Physikalische Chemie, Universität Konstanz, 78457 Konstanz, Germany
| | - A. Alia
- Leiden Institute of Chemistry, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Leiden Institute of Physics, P.O. box 9504, 2300 RA Leiden, The Netherlands, and Physikalische Chemie, Universität Konstanz, 78457 Konstanz, Germany
| | - Jörg Matysik
- Leiden Institute of Chemistry, P.O. Box 9502, 2300 RA Leiden, The Netherlands, Leiden Institute of Physics, P.O. box 9504, 2300 RA Leiden, The Netherlands, and Physikalische Chemie, Universität Konstanz, 78457 Konstanz, Germany
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15
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Daviso E, Diller A, Alia A, Matysik J, Jeschke G. Photo-CIDNP MAS NMR beyond the T1 limit by fast cycles of polarization extinction and polarization generation. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2008; 190:43-51. [PMID: 17967555 DOI: 10.1016/j.jmr.2007.10.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2007] [Revised: 10/01/2007] [Accepted: 10/04/2007] [Indexed: 05/06/2023]
Abstract
In nanosecond-laser flash photo-CIDNP MAS NMR, polarization generation (PG) proceeds much faster than longitudinal spin relaxation. With a nanosecond-laser setup linked to the NMR console the repetition time of the experiment is then limited by the minimum recycle delay of the NMR spectrometer and the maximum repetition rate of laser flashes. These limits can only be reached if polarization left after the NMR experiment is completely canceled before the next laser flash. We introduce a presaturation pulse sequence, based on three (pi/2) (13)C pulses and optimized timing and phase cycling that allows for such efficient polarization extinction (PE). The technique is demonstrated on selectively isotope labeled bacterial reaction centers (RCs) of Rhodobacter (Rb.) sphaeroides wildtype (WT). High-quality (13)C photo-CIDNP MAS NMR spectra are obtained using cycle rates up to 4 Hz. The PE-PG strategy proposed here provides a general experimental scheme for reduction of measurement time in magnetic resonance experiments based on fast PG.
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Affiliation(s)
- Eugenio Daviso
- Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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16
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Daviso E, Jeschke G, Matysik J. Photochemically Induced Dynamic Nuclear Polarization (Photo-CIDNP) Magic-Angle Spinning NMR. BIOPHYSICAL TECHNIQUES IN PHOTOSYNTHESIS 2008. [DOI: 10.1007/978-1-4020-8250-4_19] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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17
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Diller A, Prakash S, Alia A, Gast P, Matysik J, Jeschke G. Signals in Solid-State Photochemically Induced Dynamic Nuclear Polarization Recover Faster Than Signals Obtained with the Longitudinal Relaxation Time. J Phys Chem B 2007; 111:10606-14. [PMID: 17696523 DOI: 10.1021/jp072428r] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
During the photocycle of quinone-blocked photosynthetic reaction centers (RCs), photochemically induced dynamic nuclear polarization (photo-CIDNP) is produced by polarization transfer from the initially totally electron polarized electron pair and can be observed by 13C magic-angle spinning (MAS) NMR as a strong modification of signal intensities. The same processes creating net nuclear polarization open up light-dependent channels for polarization loss. This leads to coherent and incoherent enhanced signal recovery, in addition to the recovery due to light-independent longitudinal relaxation. Coherent mixing between electron and nuclear spin states due to pseudosecular hyperfine coupling within the radical pair state provides such a coherent loss channel for nuclear polarization. Another polarization transfer mechanism called differential relaxation, which is based on the long lifetime of the triplet state of the donor, provides an efficient incoherent relaxation path. In RCs of the purple bacterium Rhodobacter sphaeroides R26, the photochemical active channels allow for accelerated signal scanning by a factor of 5. Hence, photo-CIDNP MAS NMR provides the possibility to drive the NMR technique beyond the T1 limit.
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Affiliation(s)
- Anna Diller
- Leiden Institute of Chemistry, Leiden University, PO Box 9502, 2300 RA Leiden, The Netherlands
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18
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Diller A, Roy E, Gast P, van Gorkom HJ, de Groot HJM, Glaubitz C, Jeschke G, Matysik J, Alia A. 15N photochemically induced dynamic nuclear polarization magic-angle spinning NMR analysis of the electron donor of photosystem II. Proc Natl Acad Sci U S A 2007; 104:12767-71. [PMID: 17652174 PMCID: PMC1937541 DOI: 10.1073/pnas.0701763104] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In natural photosynthesis, the two photosystems that operate in series to drive electron transport from water to carbon dioxide are quite similar in structure and function, but operate at widely different potentials. In both systems photochemistry begins by photo-oxidation of a chlorophyll a, but that in photosystem II (PS2) has a 0.7 eV higher midpoint potential than that in photosystem I (PS1), so their electronic structures must be very different. Using reaction centers from (15)N-labeled spinach, these electronic structures are compared by their photochemically induced dynamic nuclear polarization (photo-CIDNP) in magic-angle spinning (MAS) NMR measurements. The results show that the electron spin distribution in PS1, apart from its known delocalization over 2 chlorophyll molecules, reveals no marked disturbance, whereas the pattern of electron spin density distribution in PS2 is inverted in the oxidized radical state. A model for the donor of PS2 is presented explaining the inversion of electron spin density based on a tilt of the axial histidine toward pyrrole ring IV causing pi-pi overlap of both aromatic systems.
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Affiliation(s)
- Anna Diller
- *Gorlaeus Laboratoria, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Esha Roy
- *Gorlaeus Laboratoria, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Peter Gast
- Huygens Laboratorium, Leiden Institute of Physics, Niels Bohrweg 2, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Hans J. van Gorkom
- Huygens Laboratorium, Leiden Institute of Physics, Niels Bohrweg 2, P.O. Box 9504, 2300 RA Leiden, The Netherlands
| | - Huub J. M. de Groot
- *Gorlaeus Laboratoria, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
| | - Clemens Glaubitz
- Institute of Biophysical Chemistry, Johann Wolfgang Goethe Universität, Max-von-Laue-Strasse 9, 60438 Frankfurt/Main, Germany; and
| | - Gunnar Jeschke
- Department of Chemistry, Universität Konstanz, Universitätsstrasse 10, 78457 Konstanz, Germany
| | - Jörg Matysik
- *Gorlaeus Laboratoria, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
- To whom correspondence should be addressed. E-mail:
| | - A. Alia
- *Gorlaeus Laboratoria, Leiden Institute of Chemistry, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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Roy E, Gast P, van Gorkom H, de Groot HJM, Jeschke G, Matysik J. Photochemically induced dynamic nuclear polarization in the reaction center of the green sulphur bacterium Chlorobium tepidum observed by 13C MAS NMR. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2007; 1767:610-5. [PMID: 17292850 DOI: 10.1016/j.bbabio.2006.12.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Revised: 12/21/2006] [Accepted: 12/29/2006] [Indexed: 11/30/2022]
Abstract
Photochemically induced dynamic nuclear polarization has been observed in reaction centres of the green sulphur bacterium Chlorobium tepidum by (13)C magic-angle spinning solid-state NMR under continuous illumination with white light. An almost complete set of chemical shifts of the aromatic ring carbons of a BChl a molecule has been obtained. All light-induced (13)C NMR signals appear to be emissive, which is similar to the pattern observed in the reaction centers of plant photosystem I and purple bacterial reaction centres of Rhodobacter sphaeroides wild type. The donor in RCs of green sulfur bacteria clearly differs from the substantially asymmetric special pair of purple bacteria and appears to be similar to the more symmetric donor of photosystem I.
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Affiliation(s)
- Esha Roy
- Leiden Institute of Chemistry, Gorlaeus Laboratoria, 2300 RA Leiden, The Netherlands
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Prakash S, Alia A, Gast P, de Groot HJM, Matysik J, Jeschke G. Photo-CIDNP MAS NMR in Intact Cells ofRhodobactersphaeroidesR26: Molecular and Atomic Resolution at Nanomolar Concentration. J Am Chem Soc 2006; 128:12794-9. [PMID: 17002374 DOI: 10.1021/ja0623616] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Photochemically induced dynamic nuclear polarization (photo-CIDNP) is observed in photosynthetic reaction centers of the carotenoid-less strain R26 of the purple bacterium Rhodobacter sphaeroides by (13)C solid-state NMR at three different magnetic fields (4.7, 9.4, and 17.6 T). The signals of the donor appear enhanced absorptive (positive) and of the acceptor emissive (negative). This spectral feature is in contrast to photo-CIDNP data of reactions centers of Rhodobacter sphaeroides wildtype reported previously (Prakash, S.; Alia; Gast, P.; de Groot, H. J. M.; Jeschke, G.; Matysik, J. J. Am. Chem. Soc. 2005, 127, 14290-14298) in which all signals appear emissive. The difference is due to an additional mechanism occurring in RCs of R26 in the long-living triplet state of the donor, allowing for spectral editing by different enhancement mechanisms. The overall shape of the spectra remains independent of the magnetic field. The strongest enhancement is observed at 4.7 T, enabling the observation of photo-CIDNP enhanced NMR signals from reaction center cofactors in entire bacterial cells allowing for detection of subtle changes in the electronic structure at nanomolar concentration of the donor cofactor. Therefore, we establish in this paper photo-CIDNP MAS NMR as a method to study the electronic structure of photosynthetic cofactors at the molecular and atomic resolution as well as at cellular concentrations.
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Affiliation(s)
- Shipra Prakash
- Leiden Institute of Chemistry, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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21
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Prakash S, Gast P, de Groot HJM, Jeschke G, Matysik J. Magnetic Field Dependence of Photo-CIDNP MAS NMR on Photosynthetic Reaction Centers ofRhodobacter sphaeroidesWT. J Am Chem Soc 2005; 127:14290-8. [PMID: 16218623 DOI: 10.1021/ja054015e] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Photochemically induced dynamic nuclear polarization (photo-CIDNP) is observed in frozen and quinone depleted photosynthetic reaction centers of the purple bacteria Rhodobacter sphaeroides wild type (WT) by (13)C solid-state NMR at three different magnetic fields. All light-induced signals appear to be emissive at all three fields. At 4.7 T (200 MHz proton frequency), the strongest enhancement of NMR signals is observed, which is more than 10 000 above the Boltzmann polarization. At higher fields, the enhancement factor decreases. At 17.6 T, the enhancement factor is about 60. The field dependence of the enhancement appears to be the same for all nuclei. The observed field dependence is in line with simulations that assume two competing mechanisms of polarization transfer from electrons to nuclei, three-spin mixing (TSM) and differential decay (DD). These simulations indicate a ratio of the electron spin density on the special pair cofactors is 3:2 in favor of the L-BChl during the radical cation state. The good agreement of simulations with the experiments raises expectations that artificial solid reaction centers can be tuned to show photo-CIDNP in the near future.
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Affiliation(s)
- Shipra Prakash
- Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands
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