1
|
Dai J, Wilhelm KB, Bischoff AJ, Pereira JH, Dedeo MT, García-Almedina DM, Adams PD, Groves JT, Francis MB. A Membrane-Associated Light-Harvesting Model is Enabled by Functionalized Assemblies of Gene-Doubled TMV Proteins. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2023; 19:e2207805. [PMID: 36811150 DOI: 10.1002/smll.202207805] [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: 12/13/2022] [Revised: 01/26/2023] [Indexed: 05/18/2023]
Abstract
Photosynthetic light harvesting requires efficient energy transfer within dynamic networks of light-harvesting complexes embedded within phospholipid membranes. Artificial light-harvesting models are valuable tools for understanding the structural features underpinning energy absorption and transfer within chromophore arrays. Here, a method for attaching a protein-based light-harvesting model to a planar, fluid supported lipid bilayer (SLB) is developed. The protein model consists of the tobacco mosaic viral capsid proteins that are gene-doubled to create a tandem dimer (dTMV). Assemblies of dTMV break the facial symmetry of the double disk to allow for differentiation between the disk faces. A single reactive lysine residue is incorporated into the dTMV assemblies for the site-selective attachment of chromophores for light absorption. On the opposing dTMV face, a cysteine residue is incorporated for the bioconjugation of a peptide containing a polyhistidine tag for association with SLBs. The dual-modified dTMV complexes show significant association with SLBs and exhibit mobility on the bilayer. The techniques used herein offer a new method for protein-surface attachment and provide a platform for evaluating excited state energy transfer events in a dynamic, fully synthetic artificial light-harvesting system.
Collapse
Affiliation(s)
- Jing Dai
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Kiera B Wilhelm
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Amanda J Bischoff
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Jose H Pereira
- Technology Division, Joint BioEnergy Institute, Emeryville, CA, 94720, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| | - Michel T Dedeo
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720, USA
| | | | - Paul D Adams
- Technology Division, Joint BioEnergy Institute, Emeryville, CA, 94720, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
- Department of Bioengineering, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Jay T Groves
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720, USA
| | - Matthew B Francis
- Department of Chemistry, University of California, Berkeley, Berkeley, CA, 94720, USA
- Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA
| |
Collapse
|
2
|
From antenna to reaction center: Pathways of ultrafast energy and charge transfer in photosystem II. Proc Natl Acad Sci U S A 2022; 119:e2208033119. [PMID: 36215463 PMCID: PMC9586314 DOI: 10.1073/pnas.2208033119] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
The photosystem II core complex (PSII-CC) is a photosynthetic complex that contains antenna proteins, which collect energy from sunlight, and a reaction center, which converts the collected energy to redox potential. Understanding the interplay between the antenna proteins and the reaction center will facilitate the development of more efficient solar energy conversion technologies. Here, we study the sub-100-ps dynamics of PSII-CC with two-dimensional electronic-vibrational spectroscopy, which connects energy flows with physical space, allowing a direct mapping of energy transfer pathways. Our results reveal a complex dynamical scheme which includes a specific pathway that connects CP43 to the reaction center. Resolving this pathway experimentally provides insights into the energy conversion processes in natural photosynthesis. The photosystem II core complex (PSII-CC) is the smallest subunit of the oxygenic photosynthetic apparatus that contains core antennas and a reaction center, which together allow for rapid energy transfer and charge separation, ultimately leading to efficient solar energy conversion. However, there is a lack of consensus on the interplay between the energy transfer and charge separation dynamics of the core complex. Here, we report the application of two-dimensional electronic-vibrational (2DEV) spectroscopy to the spinach PSII-CC at 77 K. The simultaneous temporal and spectral resolution afforded by 2DEV spectroscopy facilitates the separation and direct assignment of coexisting dynamical processes. Our results show that the dominant dynamics of the PSII-CC are distinct in different excitation energy regions. By separating the excitation regions, we are able to distinguish the intraprotein dynamics and interprotein energy transfer. Additionally, with the improved resolution, we are able to identify the key pigments involved in the pathways, allowing for a direct connection between dynamical and structural information. Specifically, we show that C505 in CP43 and the peripheral chlorophyll ChlzD1 in the reaction center are most likely responsible for energy transfer from CP43 to the reaction center.
Collapse
|
3
|
Chmeliov J, Bricker WP, Lo C, Jouin E, Valkunas L, Ruban AV, Duffy CDP. An ‘all pigment’ model of excitation quenching in LHCII. Phys Chem Chem Phys 2015; 17:15857-67. [DOI: 10.1039/c5cp01905b] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
This work presents the first all-pigment microscopic model of a major light-harvesting complex of plants and the first attempt to capture the dissipative character of the known structure.
Collapse
Affiliation(s)
- Jevgenij Chmeliov
- Department of Theoretical Physics
- Faculty of Physics
- Vilnius University
- LT-10222 Vilnius
- Lithuania
| | - William P. Bricker
- Department of Energy
- Environmental and Chemical Engineering
- Washington University in St. Louis
- Saint Louis
- USA
| | - Cynthia Lo
- Department of Energy
- Environmental and Chemical Engineering
- Washington University in St. Louis
- Saint Louis
- USA
| | - Elodie Jouin
- The School of Biological and Chemical Sciences
- Queen Mary
- University of London
- London E1 4NS
- UK
| | - Leonas Valkunas
- Department of Theoretical Physics
- Faculty of Physics
- Vilnius University
- LT-10222 Vilnius
- Lithuania
| | - Alexander V. Ruban
- The School of Biological and Chemical Sciences
- Queen Mary
- University of London
- London E1 4NS
- UK
| | | |
Collapse
|
4
|
Huh J, Saikin SK, Brookes JC, Valleau S, Fujita T, Aspuru-Guzik A. Atomistic study of energy funneling in the light-harvesting complex of green sulfur bacteria. J Am Chem Soc 2014; 136:2048-57. [PMID: 24405318 DOI: 10.1021/ja412035q] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Phototrophic organisms such as plants, photosynthetic bacteria, and algae use microscopic complexes of pigment molecules to absorb sunlight. Within the light-harvesting complexes, which frequently have several functional and structural subunits, the energy is transferred in the form of molecular excitations with very high efficiency. Green sulfur bacteria are considered to be among the most efficient light-harvesting organisms. Despite multiple experimental and theoretical studies of these bacteria, the physical origin of the efficient and robust energy transfer in their light-harvesting complexes is not well understood. To study excitation dynamics at the systems level, we introduce an atomistic model that mimics a complete light-harvesting apparatus of green sulfur bacteria. The model contains approximately 4000 pigment molecules and comprises a double wall roll for the chlorosome, a baseplate, and six Fenna-Matthews-Olson trimer complexes. We show that the fast relaxation within functional subunits combined with the transfer between collective excited states of pigments can result in robust energy funneling to the initial excitation conditions and temperature changes. Moreover, the same mechanism describes the coexistence of multiple time scales of excitation dynamics frequently observed in ultrafast optical experiments. While our findings support the hypothesis of supertransfer, the model reveals energy transport through multiple channels on different length scales.
Collapse
Affiliation(s)
- Joonsuk Huh
- Department of Chemistry and Chemical Biology, Harvard University , Cambridge, Massachusetts 02138, United States
| | | | | | | | | | | |
Collapse
|
5
|
Bennett DIG, Amarnath K, Fleming GR. A structure-based model of energy transfer reveals the principles of light harvesting in photosystem II supercomplexes. J Am Chem Soc 2013; 135:9164-73. [PMID: 23679235 DOI: 10.1021/ja403685a] [Citation(s) in RCA: 81] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Photosystem II (PSII) initiates photosynthesis in plants through the absorption of light and subsequent conversion of excitation energy to chemical energy via charge separation. The pigment binding proteins associated with PSII assemble in the grana membrane into PSII supercomplexes and surrounding light harvesting complex II trimers. To understand the high efficiency of light harvesting in PSII requires quantitative insight into energy transfer and charge separation in PSII supercomplexes. We have constructed the first structure-based model of energy transfer in PSII supercomplexes. This model shows that the kinetics of light harvesting cannot be simplified to a single rate limiting step. Instead, substantial contributions arise from both excitation diffusion through the antenna pigments and transfer from the antenna to the reaction center (RC), where charge separation occurs. Because of the lack of a rate-limiting step, fitting kinetic models to fluorescence lifetime data cannot be used to derive mechanistic insight on light harvesting in PSII. This model will clarify the interpretation of chlorophyll fluorescence data from PSII supercomplexes, grana membranes, and leaves.
Collapse
Affiliation(s)
- Doran I G Bennett
- Department of Chemistry, University of California, Berkeley, California 94720, USA
| | | | | |
Collapse
|
6
|
Duffy CDP, Chmeliov J, Macernis M, Sulskus J, Valkunas L, Ruban AV. Modeling of Fluorescence Quenching by Lutein in the Plant Light-Harvesting Complex LHCII. J Phys Chem B 2012; 117:10974-86. [DOI: 10.1021/jp3110997] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Affiliation(s)
- C. D. P. Duffy
- The School of Biological and
Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, U.K
| | - J. Chmeliov
- Theoretical Physics Department,
Faculty of Physics, Vilnius University,
Saulėteko al. 9, LT-10222 Vilnius, Lithuania
- Institute of Physics, Center for Physical Sciences and Technology, Gostauto
11, LT-01108 Vilnius, Lithuania
| | - M. Macernis
- Theoretical Physics Department,
Faculty of Physics, Vilnius University,
Saulėteko al. 9, LT-10222 Vilnius, Lithuania
- Institute of Physics, Center for Physical Sciences and Technology, Gostauto
11, LT-01108 Vilnius, Lithuania
| | - J. Sulskus
- Theoretical Physics Department,
Faculty of Physics, Vilnius University,
Saulėteko al. 9, LT-10222 Vilnius, Lithuania
| | - L. Valkunas
- Theoretical Physics Department,
Faculty of Physics, Vilnius University,
Saulėteko al. 9, LT-10222 Vilnius, Lithuania
- Institute of Physics, Center for Physical Sciences and Technology, Gostauto
11, LT-01108 Vilnius, Lithuania
| | - A. V. Ruban
- The School of Biological and
Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, U.K
| |
Collapse
|
7
|
Fleming GR, Schlau-Cohen GS, Amarnath K, Zaks J. Design principles of photosynthetic light-harvesting. Faraday Discuss 2012; 155:27-41; discussion 103-14. [DOI: 10.1039/c1fd00078k] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
|
8
|
Panitchayangkoon G, Hayes D, Fransted KA, Caram JR, Harel E, Wen J, Blankenship RE, Engel GS. Long-lived quantum coherence in photosynthetic complexes at physiological temperature. Proc Natl Acad Sci U S A 2010; 107:12766-70. [PMID: 20615985 PMCID: PMC2919932 DOI: 10.1073/pnas.1005484107] [Citation(s) in RCA: 571] [Impact Index Per Article: 40.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Photosynthetic antenna complexes capture and concentrate solar radiation by transferring the excitation to the reaction center that stores energy from the photon in chemical bonds. This process occurs with near-perfect quantum efficiency. Recent experiments at cryogenic temperatures have revealed that coherent energy transfer--a wave-like transfer mechanism--occurs in many photosynthetic pigment-protein complexes. Using the Fenna-Matthews-Olson antenna complex (FMO) as a model system, theoretical studies incorporating both incoherent and coherent transfer as well as thermal dephasing predict that environmentally assisted quantum transfer efficiency peaks near physiological temperature; these studies also show that this mechanism simultaneously improves the robustness of the energy transfer process. This theory requires long-lived quantum coherence at room temperature, which never has been observed in FMO. Here we present evidence that quantum coherence survives in FMO at physiological temperature for at least 300 fs, long enough to impact biological energy transport. These data prove that the wave-like energy transfer process discovered at 77 K is directly relevant to biological function. Microscopically, we attribute this long coherence lifetime to correlated motions within the protein matrix encapsulating the chromophores, and we find that the degree of protection afforded by the protein appears constant between 77 K and 277 K. The protein shapes the energy landscape and mediates an efficient energy transfer despite thermal fluctuations.
Collapse
Affiliation(s)
- Gitt Panitchayangkoon
- Department of Chemistry and The James Franck Institute, University of Chicago, Chicago, IL 60637; and
| | - Dugan Hayes
- Department of Chemistry and The James Franck Institute, University of Chicago, Chicago, IL 60637; and
| | - Kelly A. Fransted
- Department of Chemistry and The James Franck Institute, University of Chicago, Chicago, IL 60637; and
| | - Justin R. Caram
- Department of Chemistry and The James Franck Institute, University of Chicago, Chicago, IL 60637; and
| | - Elad Harel
- Department of Chemistry and The James Franck Institute, University of Chicago, Chicago, IL 60637; and
| | - Jianzhong Wen
- Departments of Biology and Chemistry, Washington University, St. Louis, MO 63130
| | | | - Gregory S. Engel
- Department of Chemistry and The James Franck Institute, University of Chicago, Chicago, IL 60637; and
| |
Collapse
|
9
|
Schlau-Cohen GS, Calhoun TR, Ginsberg NS, Read EL, Ballottari M, Bassi R, van Grondelle R, Fleming GR. Pathways of energy flow in LHCII from two-dimensional electronic spectroscopy. J Phys Chem B 2010; 113:15352-63. [PMID: 19856954 DOI: 10.1021/jp9066586] [Citation(s) in RCA: 134] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Photosynthetic light-harvesting complexes absorb energy and guide photoexcitations to reaction centers with speed and efficacy that produce near-perfect efficiency. Light harvesting complex II (LHCII) is the most abundant light-harvesting complex and is responsible for absorbing the majority of light energy in plants. We apply two-dimensional electronic spectroscopy to examine energy flow in LHCII. This technique allows for direct mapping of excitation energy pathways as a function of absorption and emission wavelength. The experimental and theoretical results reveal that excitation energy transfers through the complex on three time scales: previously unobserved sub-100 fs relaxation through spatially overlapping states, several hundred femtosecond transfer between nearby chlorophylls, and picosecond energy transfer steps between layers of pigments. All energy is observed to collect into the energetically lowest and most delocalized states, which serve as exit sites. We examine the angular distribution of optimal energy transfer produced by this delocalized electronic structure and discuss how it facilitates the exit step in which the energy moves from LHCII to other complexes toward the reaction center.
Collapse
|
10
|
Abramavicius D, Mukamel S. Exciton delocalization and transport in photosystem I of cyanobacteria Synechococcus elongates: simulation study of coherent two-dimensional optical signals. J Phys Chem B 2009; 113:6097-108. [PMID: 19351124 PMCID: PMC2905166 DOI: 10.1021/jp811339p] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
Electronic excitations and the optical properties of the photosynthetic complex PSI are analyzed using an effective exciton model developed by Vaitekonis et al. [Photosynth. Res. 2005, 86, 185]. States of the reaction center, the linker states, the highly delocalized antenna states and the red states are identified and assigned in absorption and circular dichroism spectra by taking into account the spectral distribution of density of exciton states, exciton delocalization length, and participation ratio in the reaction center. Signatures of exciton cooperative dynamics in nonchiral and chirality-induced two-dimensional (2D) photon-echo signals are identified. Nonchiral signals show resonances associated with the red, the reaction center, and the bulk antenna states as well as transport between them. Spectrally overlapping contributions of the linker and the delocalized antenna states are clearly resolved in the chirality-induced signals. Strong correlations are observed between the delocalized antenna states, the linker states, and the RC states. The active space of the complex covering the RC, the linker, and the delocalized antenna states is common to PSI complexes in bacteria and plants.
Collapse
Affiliation(s)
- Darius Abramavicius
- Chemistry Department, University of California Irvine, California 92697-2025, USA.
| | | |
Collapse
|
11
|
Renger T, Holzwarth AR. Theory of Excitation Energy Transfer and Optical Spectra of Photosynthetic Systems. BIOPHYSICAL TECHNIQUES IN PHOTOSYNTHESIS 2008. [DOI: 10.1007/978-1-4020-8250-4_21] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
|
12
|
Read EL, Engel GS, Calhoun TR, Mančal T, Ahn TK, Blankenship RE, Fleming GR. Cross-peak-specific two-dimensional electronic spectroscopy. Proc Natl Acad Sci U S A 2007; 104:14203-8. [PMID: 17548830 PMCID: PMC1964816 DOI: 10.1073/pnas.0701201104] [Citation(s) in RCA: 129] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Intermolecular electronic coupling dictates the optical properties of molecular aggregate systems. Of particular interest are photosynthetic pigment-protein complexes that absorb sunlight then efficiently direct energy toward the photosynthetic reaction center. Two-dimensional (2D) ultrafast spectroscopy has been used widely in the infrared (IR) and increasingly in the visible to probe excitonic couplings and observe dynamics, but the off-diagonal spectral signatures of coupling are often obscured by broad diagonal peaks, especially in the visible regime. Rotating the polarizations of the laser pulses exciting the sample can highlight certain spectral features, and the use of polarized pulse sequences to elucidate cross-peaks in 2D spectra has been demonstrated in the IR for vibrational transitions. Here we develop 2D electronic spectroscopy using cross-peak-specific pulse polarization conditions in an investigation of the Fenna-Matthews-Olson light harvesting complex from green photosynthetic bacteria. Our measurements successfully highlight off-diagonal features of the 2D spectra and, in combination with an analysis based on the signs of features arising from particular energy level pathways and theoretical simulation, we characterize the dominant response pathways responsible for the spectral features. Cross-peak-specific 2D electronic spectroscopy provides insight into the interchromophore couplings, as well as into the energetic pathways giving rise to the signal. With femtosecond resolution, we also observe dynamical processes that depend on these couplings and interactions with the protein environment.
Collapse
Affiliation(s)
- Elizabeth L. Read
- Department of Chemistry, University of California, Berkeley, CA 94720
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; and
| | - Gregory S. Engel
- Department of Chemistry, University of California, Berkeley, CA 94720
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; and
| | - Tessa R. Calhoun
- Department of Chemistry, University of California, Berkeley, CA 94720
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; and
| | - Tomáš Mančal
- Department of Chemistry, University of California, Berkeley, CA 94720
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; and
| | - Tae Kyu Ahn
- Department of Chemistry, University of California, Berkeley, CA 94720
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; and
| | | | - Graham R. Fleming
- Department of Chemistry, University of California, Berkeley, CA 94720
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; and
- To whom correspondence should be addressed at:
221 Hildebrand Hall, University of California, Berkeley, CA 94720. E-mail:
| |
Collapse
|
13
|
Vaswani HM, Stenger J, Fromme P, Fleming GR. One- and Two-Color Photon Echo Peak Shift Studies of Photosystem I. J Phys Chem B 2006; 110:26303-12. [PMID: 17181289 DOI: 10.1021/jp061008j] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Wavelength-dependent one- and two-color photon echo peak shift spectroscopy was performed on the chlorophyll Qy band of trimeric photosystem I from Thermosynechococcus elongatus. Sub-100 fs energy transfer steps were observed in addition to longer time scales previously measured by others. In the main PSI absorption peak (675-700 nm), the peak shift decays more slowly with increasing wavelength, implying that energy transfer between pigments of similar excitation energy is slower for pigments with lower site energies. In the far-red region (715 nm), the decay of the peak shift is more rapid and is complete by 1 ps, a consequence of the strong electron-phonon coupling present in this spectral region. Two-color photon echo peak shift data show strong excitonic coupling between pigments absorbing at 675 nm and those absorbing at 700 nm. The one- and two-color peak shifts were simulated using the previously developed energy transfer model (J. Phys. Chem. B 2002, 106, 10251; Biophysical Journal 2003, 85, 140). The simulations agree well with the experimental data. Two-color photon echo peak shift is shown to be far more sensitive to variations in the molecular Hamiltonian than one-color photon echo peak shift spectroscopy.
Collapse
Affiliation(s)
- Harsha M Vaswani
- Department of Chemistry, University of California at Berkeley and Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA
| | | | | | | |
Collapse
|
14
|
Sener MK, Park S, Lu D, Damjanovic A, Ritz T, Fromme P, Schulten K. Excitation migration in trimeric cyanobacterial photosystem I. J Chem Phys 2006; 120:11183-95. [PMID: 15268148 DOI: 10.1063/1.1739400] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
A structure-based description of excitation migration in multireaction center light harvesting systems is introduced. The description is an extension of the sojourn expansion, which decomposes excitation migration in terms of repeated detrapping and recapture events. The approach is applied to light harvesting in the trimeric form of cyanobacterial photosystem I (PSI). Excitation is found to be shared between PSI monomers and the chlorophylls providing the strongest respective links are identified. Excitation sharing is investigated by computing cross-monomer excitation trapping probabilities. It is seen that on the average there is a nearly 40% chance of excitation cross transfer and trapping, indicating efficient coupling between monomers. The robustness and optimality of the chlorophyll network of trimeric PSI is examined.
Collapse
Affiliation(s)
- Melih K Sener
- Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
| | | | | | | | | | | | | |
Collapse
|
15
|
Abstract
Oxygenic photosynthesis, the principal converter of sunlight into chemical energy on earth, is catalyzed by four multi-subunit membrane-protein complexes: photosystem I (PSI), photosystem II (PSII), the cytochrome b(6)f complex, and F-ATPase. PSI generates the most negative redox potential in nature and largely determines the global amount of enthalpy in living systems. PSII generates an oxidant whose redox potential is high enough to enable it to oxidize H(2)O, a substrate so abundant that it assures a practically unlimited electron source for life on earth. During the last century, the sophisticated techniques of spectroscopy, molecular genetics, and biochemistry were used to reveal the structure and function of the two photosystems. The new structures of PSI and PSII from cyanobacteria, algae, and plants has shed light not only on the architecture and mechanism of action of these intricate membrane complexes, but also on the evolutionary forces that shaped oxygenic photosynthesis.
Collapse
Affiliation(s)
- Nathan Nelson
- Department of Biochemistry, George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv 69978, Israel.
| | | |
Collapse
|
16
|
Sener MK, Jolley C, Ben-Shem A, Fromme P, Nelson N, Croce R, Schulten K. Comparison of the light-harvesting networks of plant and cyanobacterial photosystem I. Biophys J 2005; 89:1630-42. [PMID: 15994896 PMCID: PMC1366667 DOI: 10.1529/biophysj.105.066464] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
With the availability of structural models for photosystem I (PSI) in cyanobacteria and plants it is possible to compare the excitation transfer networks in this ubiquitous photosystem from two domains of life separated by over one billion years of divergent evolution, thus providing an insight into the physical constraints that shape the networks' evolution. Structure-based modeling methods are used to examine the excitation transfer kinetics of the plant PSI-LHCI supercomplex. For this purpose an effective Hamiltonian is constructed that combines an existing cyanobacterial model for structurally conserved chlorophylls with spectral information for chlorophylls in the Lhca subunits. The plant PSI excitation migration network thus characterized is compared to its cyanobacterial counterpart investigated earlier. In agreement with observations, an average excitation transfer lifetime of approximately 49 ps is computed for the plant PSI-LHCI supercomplex with a corresponding quantum yield of 95%. The sensitivity of the results to chlorophyll site energy assignments is discussed. Lhca subunits are efficiently coupled to the PSI core via gap chlorophylls. In contrast to the chlorophylls in the vicinity of the reaction center, previously shown to optimize the quantum yield of the excitation transfer process, the orientational ordering of peripheral chlorophylls does not show such optimality. The finding suggests that after close packing of chlorophylls was achieved, constraints other than efficiency of the overall excitation transfer process precluded further evolution of pigment ordering.
Collapse
Affiliation(s)
- Melih K Sener
- Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, USA
| | | | | | | | | | | | | |
Collapse
|