1
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Keil E, Lokstein H, Cogdell R, Hauer J, Zigmantas D, Thyrhaug E. Light harvesting in purple bacteria does not rely on resonance fine-tuning in peripheral antenna complexes. PHOTOSYNTHESIS RESEARCH 2024; 161:191-201. [PMID: 38907135 PMCID: PMC11324704 DOI: 10.1007/s11120-024-01107-4] [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: 04/19/2024] [Accepted: 06/10/2024] [Indexed: 06/23/2024]
Abstract
The ring-like peripheral light-harvesting complex 2 (LH2) expressed by many phototrophic purple bacteria is a popular model system in biological light-harvesting research due to its robustness, small size, and known crystal structure. Furthermore, the availability of structural variants with distinct electronic structures and optical properties has made this group of light harvesters an attractive testing ground for studies of structure-function relationships in biological systems. LH2 is one of several pigment-protein complexes for which a link between functionality and effects such as excitonic coherence and vibronic coupling has been proposed. While a direct connection has not yet been demonstrated, many such interactions are highly sensitive to resonance conditions, and a dependence of intra-complex dynamics on detailed electronic structure might be expected. To gauge the sensitivity of energy-level structure and relaxation dynamics to naturally occurring structural changes, we compare the photo-induced dynamics in two structurally distinct LH2 variants. Using polarization-controlled 2D electronic spectroscopy at cryogenic temperatures, we directly access information on dynamic and static disorder in the complexes. The simultaneous optimal spectral and temporal resolution of these experiments further allows us to characterize the ultrafast energy relaxation, including exciton transport within the complexes. Despite the variations in PPC molecular structure manifesting as clear differences in electronic structure and disorder, the energy-transport and-relaxation dynamics remain remarkably similar. This indicates that the light-harvesting functionality of purple bacteria within a single LH2 complex is highly robust to structural perturbations and likely does not rely on finely tuned electronic- or electron-vibrational resonance conditions.
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Affiliation(s)
- Erika Keil
- TUM School of Natural Sciences, Department of Chemistry, Technical University of Munich, Lichtenbergstrasse 4, 85748, Garching, Germany
| | - Heiko Lokstein
- Department of Chemical Physics and Optics, Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, 121 16, Prague, Czech Republic
| | - Richard Cogdell
- Institute of Molecular, Cell and Systems Biology, University of Glasgow, Room 402 Davidson Building, Glasgow, G12 8QQ, Scotland
| | - Jürgen Hauer
- TUM School of Natural Sciences, Department of Chemistry and Catalysis Research Center, Technical University of Munich, Lichtenbergstrasse 4, 85748, Garching, Germany
| | - Donatas Zigmantas
- Chemical Physics, Lund University, Naturvetarvägen 16, 22362, Lund, Sweden
| | - Erling Thyrhaug
- TUM School of Natural Sciences, Department of Chemistry and Catalysis Research Center, Technical University of Munich, Lichtenbergstrasse 4, 85748, Garching, Germany.
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2
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Sun K, Vasquez L, Borrelli R, Chen L, Zhao Y, Gelin MF. Interconnection between Polarization-Detected and Population-Detected Signals: Theoretical Results and Ab Initio Simulations. J Chem Theory Comput 2024. [PMID: 39185737 DOI: 10.1021/acs.jctc.4c00592] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/27/2024]
Abstract
Most of spectroscopic signals are specified by the nonlinear laser-induced polarization. In recent years, population-detection of signals becomes a trend in femtosecond spectroscopy. Polarization-detected (PD) and population-detected signals are fundamentally different, because they are determined by photoinduced processes acting on disparate time scales. In this work, we consider the fluorescence-detected (FD) N-wave-mixing (NWM) signal as a representative example of population-detected signals, derive a rigorous expression for this signal, and discuss its approximate variants suitable for numerical simulations. This leads us to the definition of the phenomenological FD (PFD) signal, which contains as a special case all definitions of FD signals available in the literature. Then we formulate and prove the population-polarization equivalence (PPE) theorem, which states that PFD NWM signals produced by (possibly strong) laser pulses can be evaluated as conventional PD signals in which the effective polarization is determined by the PFD transition dipole moment operator. We use the PPE theorem for the construction of the ab initio protocol for the simulation of PFD 4WM signals. As an example, we calculate electronic two-dimensional (2D) PFD spectra of the gas-phase pyrazine and compare them with the corresponding PD 2D spectra.
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Affiliation(s)
- Kewei Sun
- School of Science, Hangzhou Dianzi University, Hangzhou 310018, China
| | - Luis Vasquez
- School of Science, Hangzhou Dianzi University, Hangzhou 310018, China
| | | | | | - Yang Zhao
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
| | - Maxim F Gelin
- School of Science, Hangzhou Dianzi University, Hangzhou 310018, China
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3
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Gelin MF, Chen L, Domcke W. Equation-of-Motion Methods for the Calculation of Femtosecond Time-Resolved 4-Wave-Mixing and N-Wave-Mixing Signals. Chem Rev 2022; 122:17339-17396. [PMID: 36278801 DOI: 10.1021/acs.chemrev.2c00329] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Femtosecond nonlinear spectroscopy is the main tool for the time-resolved detection of photophysical and photochemical processes. Since most systems of chemical interest are rather complex, theoretical support is indispensable for the extraction of the intrinsic system dynamics from the detected spectroscopic responses. There exist two alternative theoretical formalisms for the calculation of spectroscopic signals, the nonlinear response-function (NRF) approach and the spectroscopic equation-of-motion (EOM) approach. In the NRF formalism, the system-field interaction is assumed to be sufficiently weak and is treated in lowest-order perturbation theory for each laser pulse interacting with the sample. The conceptual alternative to the NRF method is the extraction of the spectroscopic signals from the solutions of quantum mechanical, semiclassical, or quasiclassical EOMs which govern the time evolution of the material system interacting with the radiation field of the laser pulses. The NRF formalism and its applications to a broad range of material systems and spectroscopic signals have been comprehensively reviewed in the literature. This article provides a detailed review of the suite of EOM methods, including applications to 4-wave-mixing and N-wave-mixing signals detected with weak or strong fields. Under certain circumstances, the spectroscopic EOM methods may be more efficient than the NRF method for the computation of various nonlinear spectroscopic signals.
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Affiliation(s)
- Maxim F Gelin
- School of Science, Hangzhou Dianzi University, Hangzhou 310018, China
| | - Lipeng Chen
- Max-Planck-Institut für Physik komplexer Systeme, Nöthnitzer Strasse 38, D-01187 Dresden, Germany
| | - Wolfgang Domcke
- Department of Chemistry, Technical University of Munich, D-85747 Garching,Germany
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4
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Yoneda Y, Noji T, Mizutani N, Kato D, Kondo M, Miyasaka H, Nagasawa Y, Dewa T. Energy transfer dynamics and the mechanism of biohybrid photosynthetic antenna complexes chemically linked with artificial chromophores. Phys Chem Chem Phys 2022; 24:24714-24726. [PMID: 36128743 DOI: 10.1039/d2cp02465a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A light-harvesting strategy is crucial for the utilisation of solar energy. In this study, we addressed the expanding light-harvesting (LH) wavelength of photosynthetic LH complex 2 (LH2, from Rhodoblastus acidophilus strain 10050) through covalent conjugation with extrinsic chromophores. To further understand the conjugation architecture and mechanism of excitation energy transfer (EET), we examined the effects of the linker length and spectral overlap integral between the emission and absorption spectra of the energy donor and acceptor pigments. In the former case, contrary to the intuition based on the Förster resonance energy transfer (FRET) theory, the observed energy transfer rate was similar regardless of the linker length, and the energy transfer efficiency increased with longer linkers. In the latter case, despite the energy transfer rate increases at higher spectral overlaps, it was quantitatively inconsistent with the FRET theory. The mechanism of EET beyond the FRET theory was discussed in terms of the higher-lying exciton state of B850, which mediates efficient EET despite the small spectral overlap. This systematic investigation provides insights for the development of efficient artificial photosynthetic systems.
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Affiliation(s)
- Yusuke Yoneda
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.,Research Center of Integrative Molecular Systems, Institute for Molecular Science, National Institute of Natural Sciences, Okazaki, Aichi, 444-8585, Japan.
| | - Tomoyasu Noji
- Department of Life Science and Applied Chemistry, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan.
| | - Naoto Mizutani
- Department of Life Science and Applied Chemistry, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan.
| | - Daiji Kato
- Department of Life Science and Applied Chemistry, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan.
| | - Masaharu Kondo
- Department of Life Science and Applied Chemistry, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan.
| | - Hiroshi Miyasaka
- Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Yutaka Nagasawa
- College of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
| | - Takehisa Dewa
- Department of Life Science and Applied Chemistry, Graduate School of Engineering, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, Aichi 466-8555, Japan.
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5
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Exact simulation of pigment-protein complexes unveils vibronic renormalization of electronic parameters in ultrafast spectroscopy. Nat Commun 2022; 13:2912. [PMID: 35614049 PMCID: PMC9133012 DOI: 10.1038/s41467-022-30565-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Accepted: 05/04/2022] [Indexed: 12/04/2022] Open
Abstract
The primary steps of photosynthesis rely on the generation, transport, and trapping of excitons in pigment-protein complexes (PPCs). Generically, PPCs possess highly structured vibrational spectra, combining many discrete intra-pigment modes and a quasi-continuous of protein modes, with vibrational and electronic couplings of comparable strength. The intricacy of the resulting vibronic dynamics poses significant challenges in establishing a quantitative connection between spectroscopic data and underlying microscopic models. Here we show how to address this challenge using numerically exact simulation methods by considering two model systems, namely the water-soluble chlorophyll-binding protein of cauliflower and the special pair of bacterial reaction centers. We demonstrate that the inclusion of the full multi-mode vibronic dynamics in numerical calculations of linear spectra leads to systematic and quantitatively significant corrections to electronic parameter estimation. These multi-mode vibronic effects are shown to be relevant in the longstanding discussion regarding the origin of long-lived oscillations in multidimensional nonlinear spectra. Multimode vibronic mixing in model photosynthetic systems revealed by numerically exact simulations is shown to strongly modify linear and non-linear optical responses and facilitate the persistence of coherent dynamics.
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6
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Cho KH, Rhee YM. Computational elucidations on the role of vibrations in energy transfer processes of photosynthetic complexes. Phys Chem Chem Phys 2021; 23:26623-26639. [PMID: 34842245 DOI: 10.1039/d1cp04615b] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Coupling between pigment excitations and nuclear movements in photosynthetic complexes is known to modulate the excitation energy transfer (EET) efficiencies. Toward providing microscopic information, researchers often apply simulation techniques and investigate how vibrations are involved in EET processes. Here, reports on such roles of nuclear movements are discussed from a theory perspective. While vibrations naturally present random thermal fluctuations that can affect energy transferring characteristics, they can also be intertwined with exciton structures and create more specific non-adiabatic energy transfer pathways. For reliable simulations, a bath model that accurately mimics a given molecular system is required. Methods for obtaining such a model in combination with quantum chemical electronic structure calculations and molecular dynamics trajectory simulations are discussed. Various quantum dynamics simulation tools that can handle pigment-to-pigment energy transfers together with their vibrational characters are also touched on. Behaviors of molecular vibrations often deviate from ideality, especially when all-atom details are included, which practically forces us to treat them classically. We conclude this perspective by considering some recent reports that suggest that classical descriptions of bath effects with all-atom details may still produce valuable information for analyzing sophisticated contributions by vibrations to EET processes.
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Affiliation(s)
- Kwang Hyun Cho
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
| | - Young Min Rhee
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea.
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7
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The Relationship between the Spatial Arrangement of Pigments and Exciton Transition Moments in Photosynthetic Light-Harvesting Complexes. Int J Mol Sci 2021; 22:ijms221810031. [PMID: 34576194 PMCID: PMC8470053 DOI: 10.3390/ijms221810031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 09/10/2021] [Accepted: 09/13/2021] [Indexed: 11/16/2022] Open
Abstract
Considering bacteriochlorophyll molecules embedded in the protein matrix of the light-harvesting complexes of purple bacteria (known as LH2 and LH1-RC) as examples of systems of interacting pigment molecules, we investigated the relationship between the spatial arrangement of the pigments and their exciton transition moments. Based on the recently reported crystal structures of LH2 and LH1-RC and the outcomes of previous theoretical studies, as well as adopting the Frenkel exciton Hamiltonian for two-level molecules, we performed visualizations of the LH2 and LH1 exciton transition moments. To make the electron transition moments in the exciton representation invariant with respect to the position of the system in space, a system of pigments must be translated to the center of mass before starting the calculations. As a result, the visualization of the transition moments for LH2 provided the following pattern: two strong transitions were outside of LH2 and the other two were perpendicular and at the center of LH2. The antenna of LH1-RC was characterized as having the same location of the strongest moments in the center of the complex, exactly as in the B850 ring, which actually coincides with the RC. Considering LH2 and LH1 as supermolecules, each of which has excitation energies and corresponding transition moments, we propose that the outer transitions of LH2 can be important for inter-complex energy exchange, while the inner transitions keep the energy in the complex; moreover, in the case of LH1, the inner transitions increased the rate of antenna-to-RC energy transfer.
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8
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Zheng F, Chen L, Gao J, Zhao Y. Fully Quantum Modeling of Exciton Diffusion in Mesoscale Light Harvesting Systems. MATERIALS (BASEL, SWITZERLAND) 2021; 14:3291. [PMID: 34198704 PMCID: PMC8232211 DOI: 10.3390/ma14123291] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 06/06/2021] [Accepted: 06/08/2021] [Indexed: 11/16/2022]
Abstract
It has long been a challenge to accurately and efficiently simulate exciton-phonon dynamics in mesoscale photosynthetic systems with a fully quantum mechanical treatment due to extensive computational resources required. In this work, we tackle this seemingly intractable problem by combining the Dirac-Frenkel time-dependent variational method with Davydov trial states and implementing the algorithm in graphic processing units. The phonons are treated on the same footing as the exciton. Tested with toy models, which are nanoarrays of the B850 pigments from the light harvesting 2 complexes of purple bacteria, the methodology is adopted to describe exciton diffusion in huge systems containing more than 1600 molecules. The superradiance enhancement factor extracted from the simulations indicates an exciton delocalization over two to three pigments, in agreement with measurements of fluorescence quantum yield and lifetime in B850 systems. With fractal analysis of the exciton dynamics, it is found that exciton transfer in B850 nanoarrays exhibits a superdiffusion component for about 500 fs. Treating the B850 ring as an aggregate and modeling the inter-ring exciton transfer as incoherent hopping, we also apply the method of classical master equations to estimate exciton diffusion properties in one-dimensional (1D) and two-dimensional (2D) B850 nanoarrays using derived analytical expressions of time-dependent excitation probabilities. For both coherent and incoherent propagation, faster energy transfer is uncovered in 2D nanoarrays than 1D chains, owing to availability of more numerous propagating channels in the 2D arrangement.
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Affiliation(s)
- Fulu Zheng
- Bremen Center for Computational Materials Science, University of Bremen, 28359 Bremen, Germany;
| | - Lipeng Chen
- Max Planck Institute for the Physics of Complex Systems, Nöthnitzer Str., 38, 01187 Dresden, Germany;
| | - Jianbo Gao
- Center for Geodata and Analysis, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China;
- Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China
| | - Yang Zhao
- School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore
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9
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Du M, Qin M, Cui H, Wang C, Xu Y, Ma X, Yi X. Role of Spatially Correlated Fluctuations in Photosynthetic Excitation Energy Transfer with an Equilibrium and a Nonequilibrium Initial Bath. J Phys Chem B 2021; 125:6417-6430. [PMID: 34105973 DOI: 10.1021/acs.jpcb.1c02041] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The transfer of excitation energy in photosynthetic light-harvesting complexes has inspired growing interest for its scientific and engineering significance. Recent experimental findings have suggested that spatially correlated environmental fluctuations may account for the existence of long-lived quantum coherent energy transfer observed even at physiological temperature. In this paper, we investigate the effects of spatial correlations on the excitation energy transfer dynamics by including a nonequilibrium initial bath in a simulated donor-acceptor model. The initial bath state, which is assumed to be either equilibrium or nonequilibrium, is expanded in powers of coupling strength within the polaron formalism of a quantum master equation. The spatial correlations of bath fluctuations strongly influence the decay of coherence in the dynamics. The role of a nonequilibrium initial bath is also influenced by spatial correlations and becomes the most conspicuous for certain degrees of spatial correlations from which we propose a picture that the spatial correlations of bath fluctuations open up new energy transfer pathways, playing a role of protecting coherence. Besides, we apply the polaron master equation approach to study the dynamics in a two-site subsystem of the FMO complex and provide a practical example that shows the versatility of this approach.
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Affiliation(s)
- Min Du
- College of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, China
| | - Ming Qin
- College of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, China.,Center for Quantum Sciences and School of Physics, Northeast Normal University, Changchun 130024, China
| | - Haitao Cui
- College of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, China.,Center for Quantum Sciences and School of Physics, Northeast Normal University, Changchun 130024, China
| | - Chunyang Wang
- College of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, China
| | - Yuqing Xu
- College of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, China
| | - Xiaoguang Ma
- College of Physics and Optoelectronic Engineering, Ludong University, Yantai 264025, China
| | - Xuexi Yi
- Center for Quantum Sciences and School of Physics, Northeast Normal University, Changchun 130024, China
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10
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Cho KH, Rhee YM. Cooperation between Excitation Energy Transfer and Antisynchronously Coupled Vibrations. J Phys Chem B 2021; 125:5601-5610. [PMID: 34013724 DOI: 10.1021/acs.jpcb.1c01194] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The effects of the environment in energy transfer systems have been continuously studied for decades. Here, we investigate how the energy transfer and the emergence of vibrational correlations cooperate with each other based on simulations with a few numerically approximate mixed quantum classical (MQC) methods. By adopting a two-state system with locally coupled underdamped vibrations that are resonant with the electronic energy gap, we observe prominent energy dissipations from the electronic system to the vibrations, rehighlighting the role of underdamped vibrations as a temporal electronic energy buffer. More importantly, this energy dissipation generates specific phase relations between the two vibrations. Namely, the vibrations become anticorrelated right after the initiation of the energy transfer but then synchronized as the transfer completes. These phase relations are interpreted as a selective activation of an anticorrelated motion of the vibrations and a subsequent deactivation by thermal energy redistribution. Furthermore, we show that a single vibration simultaneously coupled to the two electronic states with opposite phases induces a completely equivalent energy transfer dynamics as the two localized vibrations. Finally, we discuss how the vibrational energy dissipation dynamics is affected by the adopted MQC approaches and warn about the increased subtlety toward properly treating dissipation effects over having reliable population dynamics.
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Affiliation(s)
- Kwang Hyun Cho
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
| | - Young Min Rhee
- Department of Chemistry, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Korea
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11
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Irgen-Gioro S, Gururangan K, Spencer AP, Harel E. Non-Uniform Excited State Electronic-Vibrational Coupling of Pigment-Protein Complexes. J Phys Chem Lett 2020; 11:10388-10395. [PMID: 33238100 DOI: 10.1021/acs.jpclett.0c02454] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Photosynthetic organisms exploit interacting quantum degrees of freedom, namely intrapigment electron-vibrational (vibronic) and interpigment dipolar couplings (J-coupling), to rapidly and efficiently convert light into chemical energy. These interactions result in wave function configurations that delocalize excitation between pigments and pigment vibrations. Our study uses multidimensional spectroscopy to compare two model photosynthetic proteins, the Fenna-Matthews Olson (FMO) complex and light harvesting 2 (LH2), and confirm that long-lived excited state coherences originate from the vibrational modes of the pigment. Within this framework, the J-coupling of vibronic pigments should have a cascading effect in modifying the structured spectral density of excitonic states. We show that FMO effectively couples all of its excitations to a uniform set of vibrations while in LH2, its two chromophore rings each couple to a unique vibrational environment. We simulate energy transfer in a simple model system with non-uniform vibrational coupling to demonstrate how modification of the vibronic coupling strength can modulate energy transfer. Because increasing vibronic coupling increases internal relaxation, strongly coupled vibronic states can act as an energy funnel, which can potentially benefit energy transport.
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Affiliation(s)
- Shawn Irgen-Gioro
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Karthik Gururangan
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
| | - Austin P Spencer
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
| | - Elad Harel
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, United States
- Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, United States
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12
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Scholes GD. Polaritons and excitons: Hamiltonian design for enhanced coherence. Proc Math Phys Eng Sci 2020; 476:20200278. [PMID: 33223931 PMCID: PMC7655764 DOI: 10.1098/rspa.2020.0278] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Accepted: 09/21/2020] [Indexed: 12/11/2022] Open
Abstract
The primary questions motivating this report are: Are there ways to increase coherence and delocalization of excitation among many molecules at moderate electronic coupling strength? Coherent delocalization of excitation in disordered molecular systems is studied using numerical calculations. The results are relevant to molecular excitons, polaritons, and make connections to classical phase oscillator synchronization. In particular, it is hypothesized that it is not only the magnitude of electronic coupling relative to the standard deviation of energetic disorder that decides the limits of coherence, but that the structure of the Hamiltonian-connections between sites (or molecules) made by electronic coupling-is a significant design parameter. Inspired by synchronization phenomena in analogous systems of phase oscillators, some properties of graphs that define the structure of different Hamiltonian matrices are explored. The report focuses on eigenvalues and ensemble density matrices of various structured, random matrices. Some reasons for the special delocalization properties and robustness of polaritons in the single-excitation subspace (the star graph) are discussed. The key result of this report is that, for some classes of Hamiltonian matrix structure, coherent delocalization is not easily defeated by energy disorder, even when the electronic coupling is small compared to disorder.
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13
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Gellings E, Cogdell RJ, van Hulst NF. Room-Temperature Excitation-Emission Spectra of Single LH2 Complexes Show Remarkably Little Variation. J Phys Chem Lett 2020; 11:2430-2435. [PMID: 32142282 DOI: 10.1021/acs.jpclett.0c00375] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Excitation spectroscopy gives direct insight into the excited state manifold, energy transfer, transient intermediates, vibrations, and so on. Unfortunately, excitation spectroscopy of single molecules under ambient conditions has remained challenging. Here we present excitation spectra alongside emission spectra of the same individual light-harvesting complex LH2 of the purple bacteria Rps. acidophila. The acquisition of both the excited and ground state spectra allows us to quantify disorder and interband correlations, which are key variables for the interpretation of observed long-lasting coherences. We have overcome the low photostability and small fluorescence quantum yield that are inherent to many biologically relevant systems by combining single-molecule Fourier transform spectroscopy, low excitation intensities, and effective data analysis. We find that LH2 complexes show little spectral variation (130-170 cm-1), that their two absorption bands (B800-B850) are uncorrelated, and that the Stokes shift is not constant. The low amount of spectral disorder underlines the protective role of the protein scaffold, benefiting the efficient energy transport throughout the light-harvesting membrane.
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Affiliation(s)
- Esther Gellings
- ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Barcelona, Spain
| | - Richard J Cogdell
- Davidson Building, Institute of Molecular, Cell and Systems Biology, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, United Kingdom
| | - Niek F van Hulst
- ICFO - Institut de Ciències Fotòniques, The Barcelona Institute of Science and Technology, 08860 Castelldefels, Barcelona, Spain
- ICREA - Institució Catalana de Recerca i Estudis Avançats, 08010 Barcelona, Spain
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14
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Sáez-Blázquez R, Feist J, Romero E, Fernández-Domínguez AI, García-Vidal FJ. Cavity-Modified Exciton Dynamics in Photosynthetic Units. J Phys Chem Lett 2019; 10:4252-4258. [PMID: 31291109 PMCID: PMC6907886 DOI: 10.1021/acs.jpclett.9b01495] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Accepted: 07/10/2019] [Indexed: 06/09/2023]
Abstract
Recently, exciton-photon strong coupling has been proposed as a means to control and enhance energy transfer in ensembles of organic molecules. Here, we demonstrate that the exciton dynamics in an archetypal purple bacterial photosynthetic unit, composed of six LH2 antennas surrounding a single LH1 complex, is greatly modified by its interaction with an optical cavity. We develop a Bloch-Redfield master equation approach that accounts for the interplay between the B800 and B850 bacteriochlorophyll molecules within each LH2 antenna, as well as their interactions with the central LH1 complex. Using a realistic parametrization of both the photosynthetic unit and optical cavity, we investigate the formation of polaritons in the system, revealing that these can be tuned to accelerate its exciton dynamics by 3 orders of magnitude. This yields a significant occupation of the LH1 complex, the stage immediately prior to the reaction center, with only a few-femtosecond delay after the initial excitation of the LH2 B800 pigments. Our theoretical findings unveil polaritonic phenomena as a promising route for the characterization, tailoring, and optimization of light-harvesting mechanisms in natural and artificial photosynthetic processes.
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Affiliation(s)
- Rocío Sáez-Blázquez
- Departamento
de Física Teórica de la Materia Condensada and Condensed
Matter Physics Center (IFIMAC), Universidad
Autónoma de Madrid, E-28049 Madrid, Spain
| | - Johannes Feist
- Departamento
de Física Teórica de la Materia Condensada and Condensed
Matter Physics Center (IFIMAC), Universidad
Autónoma de Madrid, E-28049 Madrid, Spain
| | - Elisabet Romero
- Institute
of Chemical Research of Catalonia (ICIQ), Barcelona Institute of Science
and Technology (BIST), E-43007 Tarragona, Spain
| | - Antonio I. Fernández-Domínguez
- Departamento
de Física Teórica de la Materia Condensada and Condensed
Matter Physics Center (IFIMAC), Universidad
Autónoma de Madrid, E-28049 Madrid, Spain
| | - Francisco J. García-Vidal
- Departamento
de Física Teórica de la Materia Condensada and Condensed
Matter Physics Center (IFIMAC), Universidad
Autónoma de Madrid, E-28049 Madrid, Spain
- Donostia
International Physics Center (DIPC), E-20018 Donostia−San Sebastián, Spain
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15
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Anda A, Hansen T, De Vico L. Qy and Qx Absorption Bands for Bacteriochlorophyll a Molecules from LH2 and LH3. J Phys Chem A 2019; 123:5283-5292. [DOI: 10.1021/acs.jpca.9b02877] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- André Anda
- Chemical and Quantum Physics, School of Science, RMIT University, Melbourne, VIC 3001, Australia
- ARC Centre of Excellence in Exciton Science, School of Science, RMIT University, Melbourne, VIC 3001, Australia
| | - Thorsten Hansen
- Department of Chemistry, Copenhagen University, Universitetsparken 5, DK-2100, Copenhagen Ø, Denmark
| | - Luca De Vico
- Department of Biotechnologies, Chemistry and Pharmacy, University of Siena, Via Aldo Moro 2, I-53100, Siena, Italy
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16
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Gelin MF, Palacino-González E, Chen L, Domcke W. Monitoring of Nonadiabatic Effects in Individual Chromophores by Femtosecond Double-Pump Single-Molecule Spectroscopy: A Model Study. Molecules 2019; 24:E231. [PMID: 30634541 PMCID: PMC6359062 DOI: 10.3390/molecules24020231] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2018] [Revised: 01/01/2019] [Accepted: 01/07/2019] [Indexed: 12/03/2022] Open
Abstract
We explore, by theoretical modeling and computer simulations, how nonadiabatic couplings of excited electronic states of a polyatomic chromophore manifest themselves in single-molecule signals on femtosecond timescales. The chromophore is modeled as a system with three electronic states (the ground state and two non-adiabatically coupled excited states) and a Condon-active vibrational mode which, in turn, is coupled to a harmonic oscillator heat bath. For this system, we simulate double-pump single-molecule signals with fluorescence detection for different system-field interaction strengths, from the weak-coupling regime to the strong-coupling regime. While the signals are determined by the coherence of the electronic density matrix in the weak-coupling regime, they are determined by the populations of the electronic density matrix in the strong-coupling regime. As a consequence, the signals in the strong coupling regime allow the monitoring of nonadiabatic electronic population dynamics and are robust with respect to temporal inhomogeneity of the optical gap, while signals in the weak-coupling regime are sensitive to fluctuations of the optical gap and do not contain information on the electronic population dynamics.
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Affiliation(s)
- Maxim F Gelin
- Department of Chemistry, Technische Universität München, D-85747 Garching, Germany.
| | | | - Lipeng Chen
- Department of Chemistry, Technische Universität München, D-85747 Garching, Germany.
| | - Wolfgang Domcke
- Department of Chemistry, Technische Universität München, D-85747 Garching, Germany.
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17
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Irgen-Gioro S, Spencer AP, Hutson WO, Harel E. Coherences of Bacteriochlorophyll a Uncovered Using 3D-Electronic Spectroscopy. J Phys Chem Lett 2018; 9:6077-6081. [PMID: 30273488 DOI: 10.1021/acs.jpclett.8b02217] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Mapping the multidimensional energy landscape of photosynthetic systems is crucial for understanding their high efficiencies. Multidimensional coherent spectroscopy is well suited to this task but has difficulty distinguishing between vibrational and electronic degrees of freedom. In pigment-protein complexes, energy differences between vibrations within a single electronic manifold are similar to differences between electronic states, leading to ambiguous assignments of spectral features and diverging physical interpretations. An important control experiment is that of the pigment monomer, but previous attempts using multidimensional coherent spectroscopy lacked the sensitivity to capture the relevant spectroscopic signatures. Here we apply a variety of methods to rapidly acquire 3D electronic-vibrational spectra in seconds, leading to a mapping of the vibrational states of Bacteriochlorophyll a (BChl a) in solution. Using this information, we can distinguish features of proteins containing BChl a from the monomer subunit and show that many of the previously reported contentious spectral signatures are vibrations of individual pigments.
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Affiliation(s)
- Shawn Irgen-Gioro
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , United States
| | - Austin P Spencer
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , United States
| | - William O Hutson
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , United States
| | - Elad Harel
- Department of Chemistry , Northwestern University , 2145 Sheridan Road , Evanston , Illinois 60208 , United States
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18
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Chen L, Gelin MF, Domcke W, Zhao Y. Simulation of Femtosecond Phase-Locked Double-Pump Signals of Individual Light-Harvesting Complexes LH2. J Phys Chem Lett 2018; 9:4488-4494. [PMID: 30037231 DOI: 10.1021/acs.jpclett.8b01887] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Recent phase-locked femtosecond double-pump experiments on individual light-harvesting complexes LH2 of purple bacteria at ambient temperature revealed undamped oscillatory responses on a time scale of at least 400 fs [ Hildner et al. Science 2013 , 340 , 1448 ]. Using an excitonic Hamiltonian for LH2 available in the literature, we simulate these signals numerically by a method that treats excitonic couplings and exciton-phonon couplings in a nonperturbative manner. The simulations provide novel insights into the origin of coherent dynamics in individual LH2 complexes.
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Affiliation(s)
- Lipeng Chen
- Department of Chemistry , Technische Universität München , D-85747 Garching , Germany
- Division of Materials Science , Nanyang Technological University , Singapore 639798 , Singapore
| | - Maxim F Gelin
- Department of Chemistry , Technische Universität München , D-85747 Garching , Germany
| | - Wolfgang Domcke
- Department of Chemistry , Technische Universität München , D-85747 Garching , Germany
| | - Yang Zhao
- Division of Materials Science , Nanyang Technological University , Singapore 639798 , Singapore
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