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Miloslavina YA, Thomas B, Reus M, Gupta KBSS, Oostergetel GT, Andreas LB, Holzwarth AR, de Groot HJM. Contrasting packing modes for tubular assemblies in chlorosomes. PHOTOSYNTHESIS RESEARCH 2024; 161:105-115. [PMID: 38538911 PMCID: PMC11269348 DOI: 10.1007/s11120-024-01089-3] [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: 10/14/2023] [Accepted: 02/27/2024] [Indexed: 07/25/2024]
Abstract
The largest light-harvesting antenna in nature, the chlorosome, is a heterogeneous helical BChl self-assembly that has evolved in green bacteria to harvest light for performing photosynthesis in low-light environments. Guided by NMR chemical shifts and distance constraints for Chlorobaculum tepidum wild-type chlorosomes, the two contrasting packing modes for syn-anti parallel stacks of BChl c to form polar 2D arrays, with dipole moments adding up, are explored. Layered assemblies were optimized using local orbital density functional and plane wave pseudopotential methods. The packing mode with the lowest energy contains syn-anti and anti-syn H-bonding between stacks. It can accommodate R and S epimers, and side chain variability. For this packing, a match with the available EM data on the subunit axial repeat and optical data is obtained with multiple concentric cylinders for a rolling vector with the stacks running at an angle of 21° to the cylinder axis and with the BChl dipole moments running at an angle ß ∼ 55° to the tube axis, in accordance with optical data. A packing mode involving alternating syn and anti parallel stacks that is at variance with EM appears higher in energy. A weak cross-peak at -6 ppm in the MAS NMR with 50 kHz spinning, assigned to C-181, matches the shift of antiparallel dimers, which possibly reflects a minor impurity-type fraction in the self-assembled BChl c.
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Affiliation(s)
- Yuliya A Miloslavina
- Institute of Chemistry, Leiden University, Box 9502, 2300 RA, Leiden, The Netherlands
- Max-Planck-Institut für Multidisziplinäre Naturwissenschaften, Am Faßberg 11, 37077, Göttingen, Germany
- Eduard-Zintl-Institut für Anorganische and Physikalische Chemie, Technische Universität Darmstadt, Alarich-Weiss-Str, 64287, Darmstadt, Germany
| | - Brijith Thomas
- Institute of Chemistry, Leiden University, Box 9502, 2300 RA, Leiden, The Netherlands
- Science Division, New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi, United Arab Emirates
| | - Michael Reus
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstr. 34-36, Mülheim a. d. Ruhr, Germany
| | | | - Gert T Oostergetel
- Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, 9747 AG, Groningen, The Netherlands
| | - Loren B Andreas
- Max-Planck-Institut für Multidisziplinäre Naturwissenschaften, Am Faßberg 11, 37077, Göttingen, Germany
| | - Alfred R Holzwarth
- Max-Planck-Institut für Chemische Energiekonversion, Stiftstr. 34-36, Mülheim a. d. Ruhr, Germany
- Department of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
| | - Huub J M de Groot
- Institute of Chemistry, Leiden University, Box 9502, 2300 RA, Leiden, The Netherlands.
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Erić V, Li X, Dsouza L, Huijser A, Holzwarth AR, Buda F, Sevink GJA, de Groot HJM, Jansen TLC. Observation of Dark States in Two-Dimensional Electronic Spectra of Chlorosomes. J Phys Chem B 2024; 128:3575-3584. [PMID: 38569137 PMCID: PMC11033866 DOI: 10.1021/acs.jpcb.4c00067] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 02/27/2024] [Accepted: 03/19/2024] [Indexed: 04/05/2024]
Abstract
Observations of low-lying dark states in several photosynthetic complexes challenge our understanding of the mechanisms behind their efficient energy transfer processes. Computational models are necessary for providing novel insights into the nature and function of dark states, especially since these are not directly accessible in spectroscopy experiments. Here, we will focus on signatures of dark-type states in chlorosomes, a light-harvesting complex from green sulfur bacteria well-known for uniting a broad absorption band with very efficient energy transfer. In agreement with experiments, our simulations of two-dimensional electronic spectra capture the ultrafast exciton transfer occurring in 100s of femtoseconds within a single chlorosome cylinder. The sub-100 fs process corresponds to relaxation within the single-excitation manifold in a single chlorosome tube, where all initially created populations in the bright exciton states are quickly transferred to dark-type exciton states. Structural inhomogeneities on the local scale cause a redistribution of the oscillator strength, leading to the emergence of these dark-type exciton states, which dominate ultrafast energy transfer. The presence of the dark-type exciton states suppresses energy loss from an isolated chlorosome via fluorescence quenching, as observed experimentally. Our results further question whether relaxation to dark-exciton states is a leading process or merely competes with transfer to the baseplate within the photosynthetic apparatus of green sulfur bacteria.
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Affiliation(s)
- Vesna Erić
- Zernike
Institute for Advanced Materials, University
of Groningen, 9747 AG Groningen, The Netherlands
| | - Xinmeng Li
- Department
of Chemistry and Hylleraas Centre for Quantum Molecular Sciences, University of Oslo, Sem Sælands vei 26, 0315 Oslo, Norway
| | - Lolita Dsouza
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Annemarie Huijser
- MESA+
Institute for Nanotechnology, University
of Twente, Drienerlolaan
5, 7522 NB Enschede, The Netherlands
| | - Alfred R. Holzwarth
- Department
of Biophysical Chemistry, Max Planck Institute
for Chemical Energy Conversion, Stiftstraße 34-36, 45470 Mülheim, Germany
| | - Francesco Buda
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - G. J. Agur Sevink
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Huub J. M. de Groot
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Thomas L. C. Jansen
- Zernike
Institute for Advanced Materials, University
of Groningen, 9747 AG Groningen, The Netherlands
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Erić V, Li X, Dsouza L, Frehan SK, Huijser A, Holzwarth AR, Buda F, Sevink GJA, de Groot HJM, Jansen TLC. Manifestation of Hydrogen Bonding and Exciton Delocalization on the Absorption and Two-Dimensional Electronic Spectra of Chlorosomes. J Phys Chem B 2023; 127:1097-1109. [PMID: 36696537 PMCID: PMC9923760 DOI: 10.1021/acs.jpcb.2c07143] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Chlorosomes are supramolecular aggregates that contain thousands of bacteriochlorophyll molecules. They perform the most efficient ultrafast excitation energy transfer of all natural light-harvesting complexes. Their broad absorption band optimizes light capture. In this study, we identify the microscopic sources of the disorder causing the spectral width and reveal how it affects the excited state properties and the optical response of the system. We combine molecular dynamics, quantum chemical calculations, and response function calculations to achieve this goal. The predicted linear and two-dimensional electronic spectra are found to compare well with experimental data reproducing all key spectral features. Our analysis of the microscopic model reveals the interplay of static and dynamic disorder from the molecular perspective. We find that hydrogen bonding motifs are essential for a correct description of the spectral line shape. Furthermore, we find that exciton delocalization over tens to hundreds of molecules is consistent with the two-dimensional electronic spectra.
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Affiliation(s)
- Vesna Erić
- University
of Groningen, Zernike Institute
for Advanced Materials, 9747
AG Groningen, The Netherlands
| | - Xinmeng Li
- Department
of Chemistry and Hylleraas Centre for Quantum Molecular Sciences, University of Oslo, Sem Sælands vei 26, 0315 Oslo, Norway
| | - Lolita Dsouza
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Sean K. Frehan
- MESA+
Institute for Nanotechnology, University
of Twente, Drienerlolaan 5, 7522 NB Enschede, The Netherlands
| | - Annemarie Huijser
- MESA+
Institute for Nanotechnology, University
of Twente, Drienerlolaan 5, 7522 NB Enschede, The Netherlands
| | - Alfred R. Holzwarth
- Department
of Biophysical Chemistry, Max Planck Institute
for Chemical Energy Conversion, Stiftstraße 34-36, 45470 Mülheim, Germany
| | - Francesco Buda
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - G. J. Agur Sevink
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Huub J. M. de Groot
- Leiden
Institute of Chemistry, Leiden University, Einsteinweg 55, 2300 RA Leiden, The Netherlands
| | - Thomas L. C. Jansen
- University
of Groningen, Zernike Institute
for Advanced Materials, 9747
AG Groningen, The Netherlands,
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Somoza AD, Sun KW, Molina RA, Zhao Y. Dynamics of coherence, localization and excitation transfer in disordered nanorings. Phys Chem Chem Phys 2018; 19:25996-26013. [PMID: 28920601 DOI: 10.1039/c7cp03171h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Self-assembled supramolecular aggregates are excellent candidates for the design of efficient excitation transport devices. Both artificially prepared and natural photosynthetic aggregates in plants and bacteria present an important degree of disorder that is supposed to hinder excitation transport. Besides, molecular excitations couple to nuclear motion affecting excitation transport in a variety of ways. We present an exhaustive study of exciton dynamics in disordered nanorings with long-range interactions under the influence of a phonon bath taking the LH2 system of purple bacteria as a model. Nuclear motion is explicitly taken into account by employing the Davydov ansatz description of the polaron and quantum dynamics are obtained using a time-dependent variational method. We reveal an optimal exciton-phonon coupling that suppresses disorder-induced localization and facilitate excitation de-trapping. This excitation transfer enhancement, mediated by environmental phonons, is attributed to energy relaxation toward extended, low-energy excitons provided by the precise LH2 geometry with anti-parallel dipoles and long-range interactions. An analysis of localization and spectral statistics is followed by dynamic measures of coherence and localization, transfer efficiency and superradiance. Linear absorption, 2D photon-echo spectra and diffusion measures of the exciton are examined to monitor the diffusive behavior as a function of the strengths of disorder and exciton-phonon coupling.
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Affiliation(s)
- Alejandro D Somoza
- Division of Materials Science, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
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