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.

scholarly journals A New Perspective for Nonphotochemical Quenching in Plant Antenna Complexes

2021 ◽  
Author(s):  
Edoardo Cignoni ◽  
Margherita Lapillo ◽  
Lorenzo Cupellini ◽  
Silvia Acosta Gutierrez ◽  
Francesco Luigi Gervasio ◽  
...  
Keyword(s):  
Light Harvesting ◽  
Nonphotochemical Quenching ◽  
Dual Function ◽  
Conformational Ensemble ◽  
Single Pair ◽  
Coulomb Interactions ◽  
Excitation Energies ◽  
Light Harvesting Complexes ◽  
New Perspective ◽  
A Minor

<div>Light-harvesting complexes (LHCs) of plants exert a dual function of light-harvesting and photoprotection. While LH processes are relatively well characterized, those involved in photoprotection are less understood. The main mechanism involved in photoprotection is to dissipate the energy absorbed by chlorophylls into harmless heat through processes collectively called nonphotochemical quenching (NPQ). Here, we characterize the quenching mechanisms of CP29, a minor LHC of plants with an important role in photoprotection, through 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 analysis reveals that the mechanism 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 pair of pigments is not sufficient but many pigments 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.</div>

scholarly journals A New Perspective for Nonphotochemical Quenching in Plant Antenna Complexes

2021 ◽  
Author(s):  
Edoardo Cignoni ◽  
Margherita Lapillo ◽  
Lorenzo Cupellini ◽  
Silvia Acosta Gutierrez ◽  
Francesco Luigi Gervasio ◽  
...  
Keyword(s):  
Light Harvesting ◽  
Nonphotochemical Quenching ◽  
Dual Function ◽  
Conformational Ensemble ◽  
Single Pair ◽  
Coulomb Interactions ◽  
Excitation Energies ◽  
Light Harvesting Complexes ◽  
New Perspective ◽  
A Minor

<div>Light-harvesting complexes (LHCs) of plants exert a dual function of light-harvesting and photoprotection. While LH processes are relatively well characterized, those involved in photoprotection are less understood. The main mechanism involved in photoprotection is to dissipate the energy absorbed by chlorophylls into harmless heat through processes collectively called nonphotochemical quenching (NPQ). Here, we characterize the quenching mechanisms of CP29, a minor LHC of plants with an important role in photoprotection, through 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 analysis reveals that the mechanism 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 pair of pigments is not sufficient but many pigments 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.</div>

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.

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 Chlorophyll excitation energies and structural stability of the CP47 antenna of photosystem II: a case study in the first-principles simulation of light-harvesting complexes

2021 ◽  
Author(s):  
Abhishek Sirohiwal ◽  
Frank Neese ◽  
Dimitrios A. Pantazis
Keyword(s):  
Photosystem Ii ◽  
Electronic Properties ◽  
Excited States ◽  
Structural Stability ◽  
First Principles ◽  
Light Harvesting ◽  
Excitation Energies ◽  
Light Harvesting Complexes ◽  
Light Harvesting Antenna

Advanced QM/MM simulations explore the excited states of a photosynthetic light-harvesting antenna in its physiologically complexed state and model the consequences of extraction on conformational and electronic properties.

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 Noise-Assisted Discord-Like Correlations in Light-Harvesting Photosynthetic Complexes

2021 ◽  
Vol 3 (2) ◽  
pp. 262-271
Author(s):  
Pablo Reséndiz-Vázquez ◽  
Ricardo Román-Ancheyta ◽  
Roberto León-Montiel
Keyword(s):  
Potential Role ◽  
Energy Transport ◽  
Light Harvesting ◽  
Quantum Correlations ◽  
Transport Processes ◽  
Quantum Evolution ◽  
Light Harvesting Complexes ◽  
Transport Efficiency ◽  
Photovoltaic Materials ◽  
Photosynthetic Complexes

Transport phenomena in photosynthetic systems have attracted a great deal of attention due to their potential role in devising novel photovoltaic materials. In particular, energy transport in light-harvesting complexes is considered quite efficient due to the balance between coherent quantum evolution and decoherence, a phenomenon coined Environment-Assisted Quantum Transport (ENAQT). Although this effect has been extensively studied, its behavior is typically described in terms of the decoherence’s strength, namely weak, moderate or strong. Here, we study the ENAQT in terms of quantum correlations that go beyond entanglement. Using a subsystem of the Fenna–Matthews–Olson complex, we find that discord-like correlations maximize when the subsystem’s transport efficiency increases, while the entanglement between sites vanishes. Our results suggest that quantum discord is a manifestation of the ENAQT and highlight the importance of beyond-entanglement correlations in photosynthetic energy transport processes.

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