scholarly journals The Relationship between the Spatial Arrangement of Pigments and Exciton Transition Moments in Photosynthetic Light-Harvesting Complexes

2021 ◽  
Vol 22 (18) ◽  
pp. 10031
Author(s):  
Roman Y. Pishchalnikov ◽  
Denis D. Chesalin ◽  
Andrei P. Razjivin
Keyword(s):  
Light Harvesting ◽  
Purple Bacteria ◽  
Center Of Mass ◽  
Electron Transition ◽  
Spatial Arrangement ◽  
Excitation Energies ◽  
Light Harvesting Complexes ◽  
Exciton Transition ◽  
Transition Moments ◽  
The Relationship

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.

scholarly journals Dichotomous disorder model for single light-harvesting complexes

2019 ◽  
Vol 58 (4) ◽  
Author(s):  
Danielis Rutkauskas
Keyword(s):  
Light Harvesting ◽  
Purple Bacteria ◽  
Photosynthetic Apparatus ◽  
Theoretical Research ◽  
Spectral Signature ◽  
Reaction Centre ◽  
Excitation Energies ◽  
Light Harvesting Complexes ◽  
Protein Scaffold ◽  
Migration Pathways

Photosynthetic organisms conserve the captured energy of solar radiation into stable chemical forms. To do so, they have evolved specialized systems of pigment–protein complexes consisting of light-harvesting antennas and reaction centres. Photosynthetic antennas contain remarkably dense arrangements of light-absorbing pigments held by the protein scaffold, and their function is to absorb light and funnel the excitation energy to the reaction centre. Decades of experimental and theoretical research resulted in a detailed understanding of the energy migration pathways within the photosynthetic apparatus. The key parameters determining the excitation relaxation and transfer are inter-pigment coupling and energetic disorder or non-equality of excitation energies at equivalent pigment sites due to the interaction with the disordered protein scaffold. Circularly symmetric light-harvesting antennas from purple bacteria present a beautiful example of the interplay between these parameters. The spectral signature of this interplay could be observed with the single-molecule fluorescence microscopy techniques. The results of these measurements were interpreted with an intuitively clear dichotomous model of disorder of pigment site energies.

scholarly journals The molecular mechanisms of light adaption in light-harvesting complexes of purple bacteria revealed by a multiscale modeling

2019 ◽  
Vol 10 (42) ◽  
pp. 9650-9662 ◽  
Author(s):  
Felipe Cardoso Ramos ◽  
Michele Nottoli ◽  
Lorenzo Cupellini ◽  
Benedetta Mennucci
Keyword(s):  
Multiscale Modeling ◽  
Molecular Mechanisms ◽  
Light Harvesting ◽  
Purple Bacteria ◽  
Spectral Tuning ◽  
Light Harvesting Complexes

The spectral tuning of LH2 antenna complexes arises from H-bonding, acetyl torsion, and inter-chromophore couplings.

Protein Configuration Landscape Fluctuations Revealed by Exciton Transition Polarizations in Single Light Harvesting Complexes

2016 ◽  
Vol 120 (4) ◽  
pp. 724-732 ◽  
Author(s):  
Sumera Tubasum ◽  
Magne Torbjörnsson ◽  
Dheerendra Yadav ◽  
Rafael Camacho ◽  
Gustaf Söderlind ◽  
...  
Keyword(s):  
Light Harvesting ◽  
Light Harvesting Complexes ◽  
Exciton Transition ◽  
Protein Configuration

scholarly journals Excitonic energy transfer in light-harvesting complexes in purple bacteria

2012 ◽  
Vol 136 (24) ◽  
pp. 245104 ◽  
Author(s):  
Jun Ye ◽  
Kewei Sun ◽  
Yang Zhao ◽  
Yunjin Yu ◽  
Chee Kong Lee ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Light Harvesting ◽  
Purple Bacteria ◽  
Light Harvesting Complexes ◽  
Excitonic Energy

Excited-State Dynamics of Carotenoids in Light-Harvesting Complexes. 1. Exploring the Relationship between the S1and S* States

2006 ◽  
Vol 110 (11) ◽  
pp. 5727-5736 ◽  
Author(s):  
Emmanouil Papagiannakis ◽  
Ivo H. M. van Stokkum ◽  
Mikas Vengris ◽  
Richard J. Cogdell ◽  
Rienk van Grondelle ◽  
...  
Keyword(s):  
Excited State ◽  
Light Harvesting ◽  
Light Harvesting Complexes ◽  
Excited State Dynamics ◽  
The Relationship ◽  
S States

Energy Transfer in the Light-Harvesting Complexes of Purple Bacteria

2018 ◽  
Vol 70 (2) ◽  
pp. 225
Author(s):  
Bei-Bei He ◽  
Meng-Meng Ming ◽  
Chang-Yong Liu ◽  
Guo-Dong Wang ◽  
Li Qin ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Light Harvesting ◽  
Purple Bacteria ◽  
Light Harvesting Complexes

scholarly journals Ultrafast energy relaxation in single light-harvesting complexes

2016 ◽  
Vol 113 (11) ◽  
pp. 2934-2939 ◽  
Author(s):  
Pavel Malý ◽  
J. Michael Gruber ◽  
Richard J. Cogdell ◽  
Tomáš Mančal ◽  
Rienk van Grondelle
Keyword(s):  
Relaxation Time ◽  
Time Distribution ◽  
Light Harvesting ◽  
Purple Bacteria ◽  
Relaxation Times ◽  
Energy Relaxation ◽  
Spectroscopic Techniques ◽  
Probe Type ◽  
Relaxation Time Distribution ◽  
Light Harvesting Complexes

Energy relaxation in light-harvesting complexes has been extensively studied by various ultrafast spectroscopic techniques, the fastest processes being in the sub–100-fs range. At the same time, much slower dynamics have been observed in individual complexes by single-molecule fluorescence spectroscopy (SMS). In this work, we use a pump–probe-type SMS technique to observe the ultrafast energy relaxation in single light-harvesting complexes LH2 of purple bacteria. After excitation at 800 nm, the measured relaxation time distribution of multiple complexes has a peak at 95 fs and is asymmetric, with a tail at slower relaxation times. When tuning the excitation wavelength, the distribution changes in both its shape and position. The observed behavior agrees with what is to be expected from the LH2 excited states structure. As we show by a Redfield theory calculation of the relaxation times, the distribution shape corresponds to the expected effect of Gaussian disorder of the pigment transition energies. By repeatedly measuring few individual complexes for minutes, we find that complexes sample the relaxation time distribution on a timescale of seconds. Furthermore, by comparing the distribution from a single long-lived complex with the whole ensemble, we demonstrate that, regarding the relaxation times, the ensemble can be considered ergodic. Our findings thus agree with the commonly used notion of an ensemble of identical LH2 complexes experiencing slow random fluctuations.

3-Acetyl-chlorophyll formation in light-harvesting complexes of purple bacteria by chemical oxidation

2016 ◽  
Vol 81 (2) ◽  
pp. 176-186 ◽  
Author(s):  
Z. K. Makhneva ◽  
A. A. Ashikhmin ◽  
M. A. Bolshakov ◽  
A. A. Moskalenko
Keyword(s):  
Light Harvesting ◽  
Purple Bacteria ◽  
Chemical Oxidation ◽  
Light Harvesting Complexes ◽  
Chlorophyll Formation

scholarly journals A different perspective for nonphotochemical quenching in plant antenna complexes

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Edoardo Cignoni ◽  
Margherita Lapillo ◽  
Lorenzo Cupellini ◽  
Silvia Acosta-Gutiérrez ◽  
Francesco Luigi Gervasio ◽  
...  
Keyword(s):  
Light Harvesting ◽  
Nonphotochemical Quenching ◽  
Dual Function ◽  
Conformational Ensemble ◽  
Coulomb Interactions ◽  
Enhanced Sampling ◽  
Excitation Energies ◽  
Light Harvesting Complexes ◽  
Quenching Mechanisms ◽  
A Minor

AbstractLight-harvesting complexes of plants exert a dual function of light-harvesting (LH) and photoprotection through processes collectively called nonphotochemical quenching (NPQ). While LH processes are relatively well characterized, those involved in NPQ are less understood. Here, we characterize the quenching mechanisms of CP29, a minor LHC of plants, through the integration of two complementary enhanced-sampling techniques, dimensionality reduction schemes, electronic calculations and the analysis of cryo-EM data in the light of the predicted conformational ensemble. Our study reveals that the switch between LH and quenching state is more complex than previously thought. Several conformations of the lumenal side of the protein occur and differently affect the pigments’ relative geometries and interactions. Moreover, we show that a quenching mechanism localized on a single chlorophyll-carotenoid pair is not sufficient but many chlorophylls are simultaneously involved. In such a diffuse mechanism, short-range interactions between each carotenoid and different chlorophylls combined with a protein-mediated tuning of the carotenoid excitation energies have to be considered in addition to the commonly suggested Coulomb interactions.

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