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Ara AM, D'Haene S, van Grondelle R, Wahadoszamen M. Unveiling large charge transfer character of PSII in an iron-deficient cyanobacterial membrane: A Stark fluorescence spectroscopy study. PHOTOSYNTHESIS RESEARCH 2024; 160:77-86. [PMID: 38619701 DOI: 10.1007/s11120-024-01099-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2023] [Accepted: 03/25/2024] [Indexed: 04/16/2024]
Abstract
In this work, we applied Stark fluorescence spectroscopy to an iron-stressed cyanobacterial membrane to reveal key insights about the electronic structures and excited state dynamics of the two important pigment-protein complexes, IsiA and PSII, both of which prevail simultaneously within the membrane during iron deficiency and whose fluorescence spectra are highly overlapped and hence often hardly resolved by conventional fluorescence spectroscopy. Thanks to the ability of Stark fluorescence spectroscopy, the fluorescence signatures of the two complexes could be plausibly recognized and disentangled. The systematic analysis of the SF spectra, carried out by employing standard Liptay formalism with a realistic spectral deconvolution protocol, revealed that the IsiA in an intact membrane retains almost identical excited state electronic structures and dynamics as compared to the isolated IsiA we reported in our earlier study. Moreover, the analysis uncovered that the excited state of the PSII subunit of the intact membrane possesses a significantly large CT character. The observed notably large magnitude of the excited state CT character may signify the supplementary role of PSII in regulative energy dissipation during iron deficiency.
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Affiliation(s)
- Anjue Mane Ara
- Department of Physics, Jagannath University, Dhaka, 1100, Bangladesh
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands
| | - Sandrine D'Haene
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands
| | - Rienk van Grondelle
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands
| | - Md Wahadoszamen
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, The Netherlands.
- Department of Physics, University of Dhaka, Dhaka, 1000, Bangladesh.
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2
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Beck WF. Intramolecular charge transfer and the function of vibronic excitons in photosynthetic light harvesting. PHOTOSYNTHESIS RESEARCH 2024:10.1007/s11120-024-01095-5. [PMID: 38656684 DOI: 10.1007/s11120-024-01095-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2023] [Accepted: 03/15/2024] [Indexed: 04/26/2024]
Abstract
A widely discussed explanation for the prevalence of pairs or clusters of closely spaced electronic chromophores in photosynthetic light-harvesting proteins is the presence of ultrafast and highly directional excitation energy transfer pathways mediated by vibronic excitons, the delocalized optical excitations derived from mixing of the electronic and vibrational states of the chromophores. We discuss herein the hypothesis that internal conversion processes between exciton states on the <100 fs timescale are possible when the excitonic potential energy surfaces are controlled by the vibrational modes that induce charge transfer character in a strongly coupled system of chromophores. We discuss two examples, the peridinin-chlorophyll protein from marine dinoflagellates and the intact phycobilisome from cyanobacteria, in which the intramolecular charge-transfer (ICT) character arising from out-of-plane distortion of the conjugation of carotenoid or bilin chromophores also results in localization of the initially delocalized optical excitation on the vibrational timescale. Tuning of the ground state conformations of the chromophores to manipulate their ICT character provides a natural photoregulatory mechanism, which would control the overall quantum yield of excitation energy transfer by turning on and off the delocalized character of the optical excitations.
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Affiliation(s)
- Warren F Beck
- Department of Chemistry, Michigan State University, East Lansing, MI, 48824, USA.
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3
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Assefa GT, Botha JL, van Heerden B, Kyeyune F, Krüger TPJ, Gwizdala M. ApcE plays an important role in light-induced excitation energy dissipation in the Synechocystis PCC6803 phycobilisomes. PHOTOSYNTHESIS RESEARCH 2024; 160:17-29. [PMID: 38407779 PMCID: PMC11006782 DOI: 10.1007/s11120-024-01078-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 01/18/2024] [Indexed: 02/27/2024]
Abstract
Phycobilisomes (PBs) play an important role in cyanobacterial photosynthesis. They capture light and transfer excitation energy to the photosynthetic reaction centres. PBs are also central to some photoprotective and photoregulatory mechanisms that help sustain photosynthesis under non-optimal conditions. Amongst the mechanisms involved in excitation energy dissipation that are activated in response to excessive illumination is a recently discovered light-induced mechanism that is intrinsic to PBs and has been the least studied. Here, we used single-molecule spectroscopy and developed robust data analysis methods to explore the role of a terminal emitter subunit, ApcE, in this intrinsic, light-induced mechanism. We isolated the PBs from WT Synechocystis PCC 6803 as well as from the ApcE-C190S mutant of this strain and compared the dynamics of their fluorescence emission. PBs isolated from the mutant (i.e., ApcE-C190S-PBs), despite not binding some of the red-shifted pigments in the complex, showed similar global emission dynamics to WT-PBs. However, a detailed analysis of dynamics in the core revealed that the ApcE-C190S-PBs are less likely than WT-PBs to enter quenched states under illumination but still fully capable of doing so. This result points to an important but not exclusive role of the ApcE pigments in the light-induced intrinsic excitation energy dissipation mechanism in PBs.
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Affiliation(s)
- Gonfa Tesfaye Assefa
- Department of Physics, University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa
| | - Joshua L Botha
- Department of Physics, University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa
| | - Bertus van Heerden
- Department of Physics, University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa
- Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa
- National Institute for Theoretical and Computational Sciences (NITheCS), Stellenbosch, South Africa
| | - Farooq Kyeyune
- Department of Physics, University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa
- Department of Physics, Faculty of Science, Kyambogo University, P.O. Box 1, Kyambogo, Kampala, Uganda
| | - Tjaart P J Krüger
- Department of Physics, University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa
- Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa
- National Institute for Theoretical and Computational Sciences (NITheCS), Stellenbosch, South Africa
| | - Michal Gwizdala
- Department of Physics, University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa.
- Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Lynnwood Road, Pretoria, 0002, South Africa.
- ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Castelldefels, 08860, Spain.
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4
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Sil S, Tilluck RW, Mohan T M N, Leslie CH, Rose JB, Domínguez-Martín MA, Lou W, Kerfeld CA, Beck WF. Excitation energy transfer and vibronic coherence in intact phycobilisomes. Nat Chem 2022; 14:1286-1294. [PMID: 36123451 DOI: 10.1038/s41557-022-01026-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2021] [Accepted: 07/21/2022] [Indexed: 11/09/2022]
Abstract
The phycobilisome is an oligomeric chromoprotein complex that serves as the principal mid-visible light-harvesting system in cyanobacteria. Here we report the observation of excitation-energy-transfer pathways involving delocalized optical excitations of the bilin (linear tetrapyrrole) chromophores in intact phycobilisomes isolated from Fremyella diplosiphon. By using broadband multidimensional electronic spectroscopy with 6.7-fs laser pulses, we are able to follow the progress of excitation energy from the phycoerythrin disks at the ends of the phycobilisome's rods to the C-phycocyanin disks along their length in <600 fs. Oscillation maps show that coherent wavepacket motions prominently involving the hydrogen out-of-plane vibrations of the bilins mediate non-adiabatic relaxation of a manifold of vibronic exciton states. However, the charge-transfer character of the bilins in the allophycocyanin-containing segments localizes the excitations in the core of the phycobilisome, yielding a kinetic bottleneck that enables photoregulatory mechanisms to operate efficiently on the >10-ps timescale.
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Affiliation(s)
- Sourav Sil
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | - Ryan W Tilluck
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | - Nila Mohan T M
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | - Chase H Leslie
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | - Justin B Rose
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | | | - Wenjing Lou
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, USA
| | - Cheryl A Kerfeld
- MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, MI, USA
| | - Warren F Beck
- Department of Chemistry, Michigan State University, East Lansing, MI, USA.
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5
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Moya R, Norris AC, Spangler LC, Scholes GD, Schlau-Cohen GS. Observation of conformational dynamics in single light-harvesting proteins from cryptophyte algae. J Chem Phys 2022; 157:035102. [PMID: 35868944 PMCID: PMC9894659 DOI: 10.1063/5.0095763] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Photosynthetic organisms use pigment-protein complexes to capture the sunlight that powers most life on earth. Within these complexes, the position of the embedded pigments is all optimized for light harvesting. At the same time, the protein scaffold undergoes thermal fluctuations that vary the structure, and, thus, photophysics, of the complexes. While these variations are averaged out in ensemble measurements, single-molecule spectroscopy provides the ability to probe these conformational changes. We used single-molecule fluorescence spectroscopy to identify the photophysical substates reflective of distinct conformations and the associated conformational dynamics in phycoerythrin 545 (PE545), a pigment-protein complex from cryptophyte algae. Rapid switching between photophysical states was observed, indicating that ensemble measurements average over a conformational equilibrium. A highly quenched conformation was also identified, and its population increased under high light. This discovery establishes that PE545 has the characteristics to serve as a photoprotective site. Finally, unlike homologous proteins from the evolutionarily related cyanobacteria and red algae, quenching was not observed upon photobleaching, which may allow for robust photophysics without the need for rapid repair or replacement machinery. Collectively, these observations establish the presence of a rich and robust set of conformational states of PE545. Cryptophytes exhibit particularly diverse energetics owing to the variety of microenvironments in which they survive, and the conformational states and dynamics reported here may provide photophysical flexibility that contributes to their remarkable ability to flourish under diverse conditions.
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Affiliation(s)
- Raymundo Moya
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Audrey C. Norris
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Leah C. Spangler
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | - Gregory D. Scholes
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA
| | - Gabriela S. Schlau-Cohen
- Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA,Author to whom correspondence should be addressed:
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van Heerden B, Vickers NA, Krüger TPJ, Andersson SB. Real-Time Feedback-Driven Single-Particle Tracking: A Survey and Perspective. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2107024. [PMID: 35758534 PMCID: PMC9308725 DOI: 10.1002/smll.202107024] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/14/2021] [Revised: 04/07/2022] [Indexed: 05/14/2023]
Abstract
Real-time feedback-driven single-particle tracking (RT-FD-SPT) is a class of techniques in the field of single-particle tracking that uses feedback control to keep a particle of interest in a detection volume. These methods provide high spatiotemporal resolution on particle dynamics and allow for concurrent spectroscopic measurements. This review article begins with a survey of existing techniques and of applications where RT-FD-SPT has played an important role. Each of the core components of RT-FD-SPT are systematically discussed in order to develop an understanding of the trade-offs that must be made in algorithm design and to create a clear picture of the important differences, advantages, and drawbacks of existing approaches. These components are feedback tracking and control, ranging from simple proportional-integral-derivative control to advanced nonlinear techniques, estimation to determine particle location from the measured data, including both online and offline algorithms, and techniques for calibrating and characterizing different RT-FD-SPT methods. Then a collection of metrics for RT-FD-SPT is introduced to help guide experimentalists in selecting a method for their particular application and to help reveal where there are gaps in the techniques that represent opportunities for further development. Finally, this review is concluded with a discussion on future perspectives in the field.
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Affiliation(s)
- Bertus van Heerden
- Department of Physics, University of Pretoria, Pretoria, 0002, South Africa
- Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, 0002, South Africa
| | - Nicholas A Vickers
- Department of Mechanical Engineering, Boston University, Boston, MA, 02215, USA
| | - Tjaart P J Krüger
- Department of Physics, University of Pretoria, Pretoria, 0002, South Africa
- Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, 0002, South Africa
| | - Sean B Andersson
- Department of Mechanical Engineering, Boston University, Boston, MA, 02215, USA
- Division of Systems Engineering, Boston University, Boston, MA, 02215, USA
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7
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Grzyb J, Walczewska-Szewc K, Sławski J, Trojnar M. Quantum dot clusters as self-assembled antennae with phycocyanine and phycobilisomes as energy acceptors. Phys Chem Chem Phys 2021; 23:24505-24517. [PMID: 34700331 DOI: 10.1039/d1cp03347f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
In this study, we investigated an experimental and Monte-Carlo computational characterization of self-assembled antennae built using CdTe colloidal quantum dots (QDs). These clusters provide efficient excitation of phycocyanine (PC) or phycobilisomes (PBSs). PBSs are light-harvesting complexes (LHCs) of cyanobacteria, made of several PC units, organized in disks and rods. Each PC contains three separate cofactors. Therefore, we analyzed variations in multi-donor and multi-acceptor systems. The self-assembled QD clusters were formed mostly by electrostatic interactions, possibly due to the introduction of a positive charge on an originally negatively charged nanoparticle surface. Our results suggest that PC may accept energy from multiple nanoparticles localized at a distance significantly longer than the Förster radius. The excitation transfers between particular nanoparticles with possible delocalization. The maximal energy transfer efficiency was obtained for the PC/PBS : QD ratio from 1 to 20 depending on the QD size. This cannot be fully explained using computational simulations; hence, we discussed the hypothesis and explained the observations. Our self-assembled systems may be considered for possible applications in artificial light-harvesting systems because absorption spectra of QDs are different from the absorption characteristics of PC/PBS. In addition, huge clusters of QDs may effectively increase the optical cross-section of so-created nanohybrids.
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Affiliation(s)
- Joanna Grzyb
- Department of Biophysics, Faculty of Biotechnology, University of Wrocław, F. Joliot-Curie 14a str, 50-383 Wrocław, Poland.
| | - Katarzyna Walczewska-Szewc
- Department of Biophysics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, Grudziądzka 5 str., 87-100 Toruń, Poland.,Centre for Modern Interdisciplinary Technologies, Nicolaus Copernicus University, Wileńska 4 str., 87-100 Toruń, Poland
| | - Jakub Sławski
- Department of Biophysics, Faculty of Biotechnology, University of Wrocław, F. Joliot-Curie 14a str, 50-383 Wrocław, Poland.
| | - Martyna Trojnar
- Department of Biophysics, Faculty of Biotechnology, University of Wrocław, F. Joliot-Curie 14a str, 50-383 Wrocław, Poland.
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8
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Hirota Y, Serikawa H, Kawakami K, Ueno M, Kamiya N, Kosumi D. Ultrafast energy transfer dynamics of phycobilisome from Thermosynechococcus vulcanus, as revealed by ps fluorescence and fs pump-probe spectroscopies. PHOTOSYNTHESIS RESEARCH 2021; 148:181-190. [PMID: 33997927 DOI: 10.1007/s11120-021-00844-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 05/04/2021] [Indexed: 06/12/2023]
Abstract
Cyanobacterial photosynthetic systems efficiently capture sunlight using the pigment-protein megacomplexes, phycobilisome (PBS). The energy is subsequently transferred to photosystem I (PSI) and II (PSII), to produce electrochemical potentials. In the present study, we performed picosecond (ps) time-resolved fluorescence and femtosecond (fs) pump-probe spectroscopies on the intact PBS from a thermophilic cyanobacterium, Thermosynechococcus vulcanus, to reveal excitation energy transfer dynamics in PBS. The photophysical properties of the intact PBS were well characterized by spectroscopic measurements covering wide temporal range from femtoseconds to nanoseconds. The ps fluorescence measurements excited at 570 nm, corresponding to the higher energy of the phycocyanin (PC) absorption band, demonstrated the excitation energy transfer from the PC rods to the allophycocyanin (APC) core complex as well as the energy transfer in the APC core complex. Then, the fs pump-probe measurements revealed the detailed energy transfer dynamics in the PC rods taking place in an ultrafast time scale. The results obtained in this study provide the full picture of the funnel-type excitation energy transfer with rate constants of (0.57 ps)-1 → (7.3 ps)-1 → (53 ps)-1 → (180 ps)-1 → (1800 ps)-1.
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Affiliation(s)
- Yuma Hirota
- Department of Physics, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Hiroki Serikawa
- Department of Physics, Graduate School of Science and Technology, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Keisuke Kawakami
- Biostructual Mechanism Laboratory, RIKEN Spring-8 Center, 1-1-1, Sayo, Kouto, Hyougo, 679-5148, Japan.
| | - Masato Ueno
- Department of Physics, Faculty of Science, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan
| | - Nobuo Kamiya
- The OCU Research Center for Artificial Photosynthesis, Osaka City University, 3-3-138, Sugimoto, Sumiyoshi-ku, Osaka, 558-8585, Japan
| | - Daisuke Kosumi
- Institute of Industrial Nanomaterials, Kumamoto University, 2-39-1 Kurokami, Chuo-ku, Kumamoto, 860-8555, Japan.
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9
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Ara AM, Ahmed MK, D'Haene S, van Roon H, Ilioaia C, van Grondelle R, Wahadoszamen M. Absence of far-red emission band in aggregated core antenna complexes. Biophys J 2021; 120:1680-1691. [PMID: 33675767 DOI: 10.1016/j.bpj.2021.02.037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 01/31/2021] [Accepted: 02/22/2021] [Indexed: 10/22/2022] Open
Abstract
Reported herein is a Stark fluorescence spectroscopy study performed on photosystem II core antenna complexes CP43 and CP47 in their native and aggregated states. The systematic mathematical modeling of the Stark fluorescence spectra with the aid of conventional Liptay formalism revealed that induction of aggregation in both the core antenna complexes via detergent removal results in a single quenched species characterized by a remarkably broad and inhomogenously broadened emission lineshape peaking around 700 nm. The quenched species possesses a fairly large magnitude of charge-transfer character. From the analogy with the results from aggregated peripheral antenna complexes, the quenched species is thought to originate from the enhanced chlorophyll-chlorophyll interaction due to aggregation. However, in contrast, aggregation of both core antenna complexes did not produce a far-red emission band at ∼730 nm, which was identified in most of the aggregated peripheral antenna complexes. The 730-nm emission band of the aggregated peripheral antenna complexes was attributed to the enhanced chlorophyll-carotenoid (lutein1) interaction in the terminal emitter locus. Therefore, it is very likely that the no occurrence of the far-red band in the aggregated core antenna complexes is directly related to the absence of lutein1 in their structures. The absence of the far-red band also suggests the possibility that aggregation-induced conformational change of the core antenna complexes does not yield a chlorophyll-carotenoid interaction associated energy dissipation channel.
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Affiliation(s)
- Anjue Mane Ara
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, the Netherlands; Department of Physics, Jagannath University, Dhaka, Bangladesh
| | | | - Sandrine D'Haene
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, the Netherlands
| | - Henny van Roon
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, the Netherlands
| | - Cristian Ilioaia
- Institute for Integrative Biology of the Cell, CEA, CNRS, Université Paris-Saclay, Gif-sur-Yvette, France
| | - Rienk van Grondelle
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, the Netherlands
| | - Md Wahadoszamen
- Biophysics of Photosynthesis, Department of Physics and Astronomy, Faculty of Sciences, VU University Amsterdam, Amsterdam, the Netherlands; Department of Physics, University of Dhaka, Dhaka, Bangladesh.
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10
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Nguyen HH, Loukianov AD, Ogilvie JP, Abramavicius D. Two-dimensional electronic Stark spectroscopy of a photosynthetic dimer. J Chem Phys 2020; 153:144203. [PMID: 33086821 DOI: 10.1063/5.0021529] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Stark spectroscopy, which measures changes in the linear absorption of a sample in the presence of an external DC electric field, is a powerful experimental tool for probing the existence of charge-transfer (CT) states in photosynthetic systems. CT states often have small transition dipole moments, making them insensitive to other spectroscopic methods, but are particularly sensitive to Stark spectroscopy due to their large permanent dipole moment. In a previous study, we demonstrated a new experimental method, two-dimensional electronic Stark spectroscopy (2DESS), which combines two-dimensional electronic spectroscopy (2DES) and Stark spectroscopy. In order to understand how the presence of CT states manifest in 2DESS, here, we perform computational modeling and calculations of 2DESS as well as 2DES and Stark spectra, studying a photosynthetic dimer inspired by the photosystem II reaction center. We identify specific cases where qualitatively different sets of system parameters produce similar Stark and 2DES spectra but significantly different 2DESS spectra, showing the potential for 2DESS to aid in identifying CT states and their coupling to excitonic states.
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Affiliation(s)
- Hoang H Nguyen
- Department of Physics, University of Michigan, 450 Church St., Ann Arbor, Michigan 48109, USA
| | - Anton D Loukianov
- Department of Physics, University of Michigan, 450 Church St., Ann Arbor, Michigan 48109, USA
| | - Jennifer P Ogilvie
- Department of Physics, University of Michigan, 450 Church St., Ann Arbor, Michigan 48109, USA
| | - Darius Abramavicius
- Institute of Chemical Physics, Faculty of Physics, Vilnius University, Sauletekio 9-III, 10222 Vilnius, Lithuania
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