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.

scholarly journals Optimization of light harvesting and photoprotection: molecular mechanisms and physiological consequences

2012 ◽  
Vol 367 (1608) ◽  
pp. 3455-3465 ◽  
Author(s):  
Peter Horton
Keyword(s):  
Protein Interactions ◽  
Thylakoid Membrane ◽  
Molecular Mechanisms ◽  
Light Harvesting ◽  
Protein Complexes ◽  
Efficient Energy Transfer ◽  
Light Harvesting Complexes ◽  
Functional Flexibility ◽  
Jan Anderson ◽  
Repulsive Forces

The distinctive lateral organization of the protein complexes in the thylakoid membrane investigated by Jan Anderson and co-workers is dependent on the balance of various attractive and repulsive forces. Modulation of these forces allows critical physiological regulation of photosynthesis that provides efficient light-harvesting in limiting light but dissipation of excess potentially damaging radiation in saturating light. The light-harvesting complexes (LHCII) are central to this regulation, which is achieved by phosphorylation of stromal residues, protonation on the lumen surface and de-epoxidation of bound violaxanthin. The functional flexibility of LHCII derives from a remarkable pigment composition and configuration that not only allow efficient absorption of light and efficient energy transfer either to photosystem II or photosystem I core complexes, but through subtle configurational changes can also exhibit highly efficient dissipative reactions involving chlorophyll–xanthophyll and/or chlorophyll–chlorophyll interactions. These changes in function are determined at a macroscopic level by alterations in protein–protein interactions in the thylakoid membrane. The capacity and dynamics of this regulation are tuned to different physiological scenarios by the exact protein and pigment content of the light-harvesting system. Here, the molecular mechanisms involved will be reviewed, and the optimization of the light-harvesting system in different environmental conditions described.

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

scholarly journals The Molecular Mechanisms of Photoactivation of Orange Carotenoid Protein Revealed by Molecular Dynamics

2020 ◽  
Author(s):  
Mattia Bondanza ◽  
Lorenzo Cupellini ◽  
Pietro Faccioli ◽  
Benedetta Mennucci
Keyword(s):  
Structural Changes ◽  
Molecular Mechanisms ◽  
Light Harvesting ◽  
Experimental Studies ◽  
Green Light ◽  
Enhanced Sampling ◽  
Light Harvesting Complexes ◽  
Effective Combination ◽  
Large Conformational Change ◽  
Orange Carotenoid Protein

Light-harvesting in photosynthesis is accompanied by photoprotective processes. In cyanobacteria, the photoprotective role is played by a specialized complex, the Orange Carotenoid Protein which is activated by strong blue-green light. This photoactivation involves a unique series of structural changes which terminate with an opening of the complex into two separated domains, one of which acts as a quencher for the light-harvesting complexes. Many experimental studies have tried to reveal the molecular mechanisms through which the energy absorbed by the carotenoid finally leads to the large conformational change of the complex. Here for the first time, these mechanisms are revealed by simulating at atomistic level the whole dynamics of the complex through an effective combination of enhanced sampling techniques. On the basis of our findings, we can conclude that the carotenoid does not act as a spring that, releasing its internal strain, induces the dissociation, as it was previously proposed but as a "latch" locking together the two domains. The photochemically triggered displacement of the carotenoid breaks this balance, allowing the complex to dissociate. <br>

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.

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

The architecture and function of the light-harvesting apparatus of purple bacteria: from single molecules to in vivo membranes

2006 ◽  
Vol 39 (3) ◽  
pp. 227-324 ◽  
Author(s):  
Richard J. Cogdell ◽  
Andrew Gall ◽  
Jürgen Köhler
Keyword(s):  
Quantum Mechanics ◽  
Energy Transfer ◽  
Single Molecule ◽  
Molecular Mechanisms ◽  
Light Harvesting ◽  
Structural Information ◽  
Purple Bacteria ◽  
Theoretical Background ◽  
Single Molecule Spectroscopy

1. Introduction 2292. Structures 2342.1 The structure of LH2 2342.2 Natural variants of peripheral antenna complexes 2422.3 RC–LH1 complexes 2423. Spectroscopy 2493.1 Steady-state spectroscopy 2493.2 Factors which affect the position of the Qy absorption band of Bchla 2494. Regulation of biosynthesis and assembly 2574.1 Regulation 2574.1.1 Oxygen 2574.1.2 Light 2584.1.2.1 AppA: blue-light-mediated regulation 2594.1.2.2 Bacteriophytochromes 2594.1.3 From the RC to the mature PSU 2614.2 Assembly 2614.2.1 LH1 2624.2.2 LH2 2635. Frenkel excitons 2655.1 General 2655.2 B800 2675.3 B850 2675.4 B850 delocalization 2736. Energy-transfer pathways: experimental results 2746.1 Theoretical background 2746.2 ‘Follow the excitation energy’ 2766.2.1 Bchla→Bchla energy transfer 2776.2.1.1 B800→B800 2776.2.1.2 B800→B850 2786.2.1.3 B850→B850 2796.2.1.4 B850→B875 2806.2.1.5 B875→RC 2806.2.2 Car[harr ]Bchla energy transfer 2817. Single-molecule spectroscopy 2847.1 Introduction to single-molecule spectroscopy 2847.2 Single-molecule spectroscopy on LH2 2857.2.1 Overview 2857.2.2 B800 2867.2.2.1 General 2867.2.2.2 Intra- and intercomplex disorder of site energies 2877.2.2.3 Electron-phonon coupling 2897.2.2.4 B800→B800 energy transfer revisited 2907.2.3 B850 2938. Quantum mechanics and the purple bacteria LH system 2989. Appendix 2999.1 A crash course on quantum mechanics 2999.2 Interacting dimers 30510. Acknowledgements 30611. References 307This review describes the structures of the two major integral membrane pigment complexes, the RC–LH1 ‘core’ and LH2 complexes, which together make up the light-harvesting system present in typical purple photosynthetic bacteria. The antenna complexes serve to absorb incident solar radiation and to transfer it to the reaction centres, where it is used to ‘power’ the photosynthetic redox reaction and ultimately leads to the synthesis of ATP. Our current understanding of the biosynthesis and assembly of the LH and RC complexes is described, with special emphasis on the roles of the newly described bacteriophytochromes. Using both the structural information and that obtained from a wide variety of biophysical techniques, the details of each of the different energy-transfer reactions that occur, between the absorption of a photon and the charge separation in the RC, are described. Special emphasis is given to show how the use of single-molecule spectroscopy has provided a more detailed understanding of the molecular mechanisms involved in the energy-transfer processes. We have tried, with the help of an Appendix, to make the details of the quantum mechanics that are required to appreciate these molecular mechanisms, accessible to mathematically illiterate biologists. The elegance of the purple bacterial light-harvesting system lies in the way in which it has cleverly exploited quantum mechanics.

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
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