scholarly journals Photosynthesis tunes quantum-mechanical mixing of electronic and vibrational states to steer exciton energy transfer

2021 ◽  
Vol 118 (11) ◽  
pp. e2018240118
Author(s):  
Jacob S. Higgins ◽  
Lawson T. Lloyd ◽  
Sara H. Sohail ◽  
Marco A. Allodi ◽  
John P. Otto ◽  
...  
Keyword(s):  
Quantum Mechanics ◽  
Energy Transfer ◽  
Energy Gap ◽  
Vibrational Mode ◽  
Protein Complexes ◽  
Electronic Spectroscopy ◽  
Green Sulfur Bacteria ◽  
Cysteine Residues ◽  
Mechanical Mixing ◽  
Mutant Proteins

Photosynthetic species evolved to protect their light-harvesting apparatus from photoxidative damage driven by intracellular redox conditions or environmental conditions. The Fenna–Matthews–Olson (FMO) pigment–protein complex from green sulfur bacteria exhibits redox-dependent quenching behavior partially due to two internal cysteine residues. Here, we show evidence that a photosynthetic complex exploits the quantum mechanics of vibronic mixing to activate an oxidative photoprotective mechanism. We use two-dimensional electronic spectroscopy (2DES) to capture energy transfer dynamics in wild-type and cysteine-deficient FMO mutant proteins under both reducing and oxidizing conditions. Under reducing conditions, we find equal energy transfer through the exciton 4–1 and 4–2-1 pathways because the exciton 4–1 energy gap is vibronically coupled with a bacteriochlorophyll-a vibrational mode. Under oxidizing conditions, however, the resonance of the exciton 4–1 energy gap is detuned from the vibrational mode, causing excitons to preferentially steer through the indirect 4–2-1 pathway to increase the likelihood of exciton quenching. We use a Redfield model to show that the complex achieves this effect by tuning the site III energy via the redox state of its internal cysteine residues. This result shows how pigment–protein complexes exploit the quantum mechanics of vibronic coupling to steer energy transfer.

Heat, quantum mechanics and information

2015 ◽  
Vol 10 (2) ◽  
pp. 2692-2695
Author(s):  
Bhekuzulu Khumalo
Keyword(s):  
Information Theory ◽  
Quantum Mechanics ◽  
Energy Transfer ◽  
Transfer Process ◽  
Energy Transfer Process ◽  
Process Information ◽  
Double Slit Experiment ◽  
Slit Experiment ◽  
Double Slit

Heat has often been described as part of the energy transfer process. Information theory says everything is information. If everything is information then what type of information is heat, this question can be settled by the double slit experiment, but we must know what we are looking for. 

scholarly journals Breakdown of energy transfer gap laws revealed by full-dimensional quantum scattering between HF molecules

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Dongzheng Yang ◽  
Jing Huang ◽  
Xixi Hu ◽  
Hua Guo ◽  
Daiqian Xie
Keyword(s):  
Energy Transfer ◽  
Angular Momentum ◽  
Vibrational Energy ◽  
Energy Gap ◽  
Inelastic Collisions ◽  
Rate Coefficients ◽  
Quantum Scattering ◽  
Final States ◽  
Energy Gap Law ◽  
Quantitative Basis

Abstract Inelastic collisions involving molecular species are key to energy transfer in gaseous environments. They are commonly governed by an energy gap law, which dictates that transitions are dominated by those between initial and final states with roughly the same ro-vibrational energy. Transitions involving rotational inelasticity are often further constrained by the rotational angular momentum. Here, we demonstrate using full-dimensional quantum scattering on an ab initio based global potential energy surface (PES) that HF–HF inelastic collisions do not obey the energy and angular momentum gap laws. Detailed analyses attribute the failure of gap laws to the exceedingly strong intermolecular interaction. On the other hand, vibrational state-resolved rate coefficients are in good agreement with existing experimental results, validating the accuracy of the PES. These new and surprising results are expected to extend our understanding of energy transfer and provide a quantitative basis for numerical simulations of hydrogen fluoride chemical lasers.

scholarly journals Key Role of Cysteine Residues in Catalysis and Subcellular Localization of Sulfur Oxygenase-Reductase of Acidianus tengchongensis

2005 ◽  
Vol 71 (2) ◽  
pp. 621-628 ◽  
Author(s):  
Zhi-Wei Chen ◽  
Cheng-Ying Jiang ◽  
Qunxin She ◽  
Shuang-Jiang Liu ◽  
Pei-Jin Zhou
Keyword(s):  
Cytoplasmic Membrane ◽  
Sulfur Oxidation ◽  
Site Directed Mutagenesis ◽  
Cysteine Residues ◽  
Wild Type ◽  
Immune Electron Microscopy ◽  
Mutant Proteins ◽  
Close Proximity ◽  
Catalytic Sites

ABSTRACT Analysis of known sulfur oxygenase-reductases (SORs) and the SOR-like sequences identified from public databases indicated that they all possess three cysteine residues within two conserved motifs (V-G-P-K-V-C31 and C101-X-X-C104; numbering according to the Acidianus tengchongensis numbering system). The thio-modifying reagent N-ethylmaleimide and Zn2+ strongly inhibited the activities of the SORs of A. tengchongensis, suggesting that cysteine residues are important. Site-directed mutagenesis was used to construct four mutant SORs with cysteines replaced by serine or alanine. The purified mutant proteins were investigated in parallel with the wild-type SOR. Replacement of any cysteine reduced SOR activity by 98.4 to 100%, indicating that all the cysteine residues are crucial to SOR activities. Circular-dichroism and fluorescence spectrum analyses revealed that the wild-type and mutant SORs have similar structures and that none of them form any disulfide bond. Thus, it is proposed that three cysteine residues, C31 and C101-X-X-C104, in the conserved domains constitute the putative binding and catalytic sites of SOR. Furthermore, enzymatic activity assays of the subcellular fractions and immune electron microscopy indicated that SOR is not only present in the cytoplasm but also associated with the cytoplasmic membrane of A. tengchongensis. The membrane-associated SOR activity was colocalized with the activities of sulfite:acceptor oxidoreductase and thiosulfate:acceptor oxidoreductase. We tentatively propose that these enzymes are located in close proximity on the membrane to catalyze sulfur oxidation in A. tengchongensis.

scholarly journals Two-Dimensional Electronic Spectroscopy Reveals the Spectral Dynamics of Förster Resonance Energy Transfer

Chem ◽  
2019 ◽  
Vol 5 (8) ◽  
pp. 2111-2125 ◽  
Author(s):  
Brian K. Petkov ◽  
Tobias A. Gellen ◽  
Camille A. Farfan ◽  
William P. Carbery ◽  
Belinda E. Hetzler ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Electronic Spectroscopy ◽  
Resonance Energy Transfer ◽  
Resonance Energy ◽  
Forster Resonance Energy Transfer ◽  
Förster Resonance Energy Transfer ◽  
Two Dimensional ◽  
Spectral Dynamics ◽  
Förster Resonance

scholarly journals Ultrabroadband two-dimensional electronic spectroscopy reveals energy flow pathways in LHCII across the visible spectrum

2019 ◽  
Vol 205 ◽  
pp. 09034
Author(s):  
Minjung Son ◽  
Alberta Pinnola ◽  
Roberto Bassi ◽  
Gabriela S. Schlau-Cohen
Keyword(s):  
Energy Transfer ◽  
Excited States ◽  
Energy Flow ◽  
Energy Levels ◽  
Electronic Spectroscopy ◽  
Visible Region ◽  
Visible Spectrum ◽  
Energy Relaxation ◽  
Two Dimensional ◽  
Flow Pathways

We utilise ultrabroadband two-dimensional electronic spectroscopy to map out pathways of energy flow in LHCII across the entire visible region. In addition to the well-established, low-lying chlorophyll Qy bands, our results reveal additional pathways of energy relaxation on the higher-lying excited states involving the S2 energy levels of carotenoids, including ultrafast carotenoid-to-chlorophyll energy transfer on 90-150 fs timescales.

Preparation, characterization and application of interleukin-1beta mutant proteins with surface-accessible cysteine residues

1989 ◽  
Vol 179 (3) ◽  
pp. 565-571 ◽  
Author(s):  
Paul WINGFIELD ◽  
Pierre GRABER ◽  
Alan R. SHAW ◽  
Angela M. GRONENBORN ◽  
G. Marius CLORE ◽  
...  
Keyword(s):  
Cysteine Residues ◽  
Mutant Proteins ◽  
Interleukin 1Beta

scholarly journals A photosynthetic antenna complex foregoes unity carotenoid-to-bacteriochlorophyll energy transfer efficiency to ensure photoprotection

2020 ◽  
Vol 117 (12) ◽  
pp. 6502-6508 ◽  
Author(s):  
Dariusz M. Niedzwiedzki ◽  
David J. K. Swainsbury ◽  
Daniel P. Canniffe ◽  
C. Neil Hunter ◽  
Andrew Hitchcock
Keyword(s):  
Energy Transfer ◽  
Transient Absorption ◽  
Light Harvesting ◽  
Protein Complexes ◽  
Fluorescence Emission ◽  
Energy Transfer Efficiency ◽  
Transfer Efficiency ◽  
Light Harvesting Complexes ◽  
Antenna Complex ◽  
Pigment Protein Complexes

Carotenoids play a number of important roles in photosynthesis, primarily providing light-harvesting and photoprotective energy dissipation functions within pigment–protein complexes. The carbon–carbon double bond (C=C) conjugation length of carotenoids (N), generally between 9 and 15, determines the carotenoid-to-(bacterio)chlorophyll [(B)Chl] energy transfer efficiency. Here we purified and spectroscopically characterized light-harvesting complex 2 (LH2) fromRhodobacter sphaeroidescontaining theN= 7 carotenoid zeta (ζ)-carotene, not previously incorporated within a natural antenna complex. Transient absorption and time-resolved fluorescence show that, relative to the lifetime of the S1state of ζ-carotene in solvent, the lifetime decreases ∼250-fold when ζ-carotene is incorporated within LH2, due to transfer of excitation energy to the B800 and B850 BChlsa. These measurements show that energy transfer proceeds with an efficiency of ∼100%, primarily via the S1→ Qxroute because the S1→ S0fluorescence emission of ζ-carotene overlaps almost perfectly with the Qxabsorption band of the BChls. However, transient absorption measurements performed on microsecond timescales reveal that, unlike the nativeN≥ 9 carotenoids normally utilized in light-harvesting complexes, ζ-carotene does not quench excited triplet states of BChla, likely due to elevation of the ζ-carotene triplet energy state above that of BChla. These findings provide insights into the coevolution of photosynthetic pigments and pigment–protein complexes. We propose that theN≥ 9 carotenoids found in light-harvesting antenna complexes represent a vital compromise that retains an acceptable level of energy transfer from carotenoids to (B)Chls while allowing acquisition of a new, essential function, namely, photoprotective quenching of harmful (B)Chl triplets.

scholarly journals Excitation energy transfer and equilibration process in LHCII studied by multidimensional electronic spectroscopy

2019 ◽  
Vol 205 ◽  
pp. 09038
Author(s):  
Thanh Nhut Do ◽  
Adriana Huerta-Viga ◽  
Cheng Zhang ◽  
Parveen Akhtar ◽  
Pawei J. Nowakowski ◽  
...  
Keyword(s):  
Energy Transfer ◽  
Light Harvesting ◽  
Electronic Spectroscopy ◽  
Excitation Energy Transfer ◽  
Phenomenological Analysis ◽  
Two Dimensional ◽  
Light Harvesting Complex ◽  
Light Harvesting Complex Ii ◽  
Equilibration Process ◽  
Light Harvesting Antenna

Light-harvesting complex II (LHCII) – the light-harvesting antenna of Photosystem II – is a naturally abundant system that plays an important role in photosynthesis. In this study, we present a phenomenological analysis of the excitonic energy transfer in LHCII using ultrafast two-dimensional electronic spectroscopy, that we find compares well with previous theoretical and experimental results.

scholarly journals On uncorrelated inter-monomer Förster energy transfer in Fenna–Matthews–Olson complexes

2019 ◽  
Vol 16 (151) ◽  
pp. 20180882 ◽  
Author(s):  
Adam Kell ◽  
Anton Yu. Khmelnitskiy ◽  
Tonu Reinot ◽  
Ryszard Jankowiak
Keyword(s):  
Energy Transfer ◽  
Green Sulfur Bacteria ◽  
Coupling Constants ◽  
Electronic Coupling ◽  
Reaction Centre ◽  
Sulfur Bacteria ◽  
Fmo Protein ◽  
Reduced Density ◽  
Light Harvesting Antenna ◽  
Pigment Protein Complex

The Fenna–Matthews–Olson (FMO) light-harvesting antenna protein of green sulfur bacteria is a long-studied pigment–protein complex which funnels energy from the chlorosome to the reaction centre where photochemistry takes place. The structure of the FMO protein from Chlorobaculum tepidum is known as a homotrimeric complex containing eight bacteriochlorophyll a per monomer. Owing to this structure FMO has strong intra-monomer and weak inter-monomer electronic coupling constants. While long-lived (sub-picosecond) coherences within a monomer have been a prevalent topic of study over the past decade, various experimental evidence supports the presence of subsequent inter-monomer energy transfer on a picosecond time scale. The latter has been neglected by most authors in recent years by considering only sub-picosecond time scales or assuming that the inter-monomer coupling between low-energy states is too weak to warrant consideration of the entire trimer. However, Förster theory predicts that energy transfer of the order of picoseconds is possible even for very weak (less than 5 cm –1 ) electronic coupling between chromophores. This work reviews experimental data (with a focus on emission and hole-burned spectra) and simulations of exciton dynamics which demonstrate inter-monomer energy transfer. It is shown that the lowest energy 825 nm absorbance band cannot be properly described by a single excitonic state. The energy transfer through FMO is modelled by generalized Förster theory using a non-Markovian, reduced density matrix approach to describe the electronic structure. The disorder-averaged inter-monomer transfer time across the 825 nm band is about 27 ps. While only isolated FMO proteins are presented, the presence of inter-monomer energy transfer in the context of the overall photosystem is also briefly discussed.

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