Directed Formation of Micro- and Nanoscale Patterns of Functional Light-Harvesting LH2 Complexes

Reynolds, Nicholas P.; Janusz, Stefan; Escalante-Marun, Maryana; Timney, John A.; Ducker, Robert E.; Olsen, John D.; Otto, Cees; Subramaniam, Vinod; Leggett, Graham J.; Hunter, C. Neil

doi:10.1021/ja073658m

Cited by 54 publications

(64 citation statements)

References 40 publications

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“…(ii) The quenching dynamics observed here are particularly relevant to the ongoing incorporation of LH2 into light harvesting devices (33), which may be installed under solar concentrators that produce intensities orders of magnitude above natural levels (34). These results show that LH2, like inorganic systems, can maintain its functionality under these high fluences.…”

Section: Discussionmentioning

confidence: 99%

“…The existence of multiple photoprotective mechanisms is particularly important in situations such as artificial light harvesting systems installed under concentrated sunlight that far exceeds natural levels (34). The photostability and photoprotective aspects of LH2 characterized here for wavelengths across the solar spectrum are particularly valuable for the design of solar energy devices incorporating LH2 (33).…”

Section: Discussionmentioning

confidence: 99%

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Single-molecule spectroscopy reveals photosynthetic LH2 complexes switch between emissive states

Schlau‐Cohen¹,

Wang

Southall

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

126

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Photosynthetic organisms flourish under low light intensities by converting photoenergy to chemical energy with near unity quantum efficiency and under high light intensities by safely dissipating excess photoenergy and deleterious photoproducts. The molecular mechanisms balancing these two functions remain incompletely described. One critical barrier to characterizing the mechanisms responsible for these processes is that they occur within proteins whose excited-state properties vary drastically among individual proteins and even within a single protein over time. In ensemble measurements, these excited-state properties appear only as the average value. To overcome this averaging, we investigate the purple bacterial antenna protein light harvesting complex 2 (LH2) from Rhodopseudomonas acidophila at the single-protein level. We use a room-temperature, single-molecule technique, the antiBrownian electrokinetic trap, to study LH2 in a solution-phase (nonperturbative) environment. By performing simultaneous measurements of fluorescence intensity, lifetime, and spectra of single LH2 complexes, we identify three distinct states and observe transitions occurring among them on a timescale of seconds. Our results reveal that LH2 complexes undergo photoactivated switching to a quenched state, likely by a conformational change, and thermally revert to the ground state. This is a previously unobserved, reversible quenching pathway, and is one mechanism through which photosynthetic organisms can adapt to changes in light intensities.photosynthesis | purple bacteria | fluorescence spectroscopy I n photosynthetic light harvesting, networks of antenna pigmentprotein complexes (PPCs) absorb sunlight, then efficiently transport the excitation through these networks to the reaction center, a PPC dedicated to charge separation (1, 2). Photosynthetic systems can complete this process both with near unity quantum efficiency and also function at light levels that provide photoenergy in excess of the capacity of downstream photochemistry. This is accomplished through mechanisms that dissipate harmful by-products produced by unused photoenergy (2, 3). The absorption, energy transport, and dissipation properties are governed by the balance of pigment-pigment and pigment-protein couplings (4). However, the molecular machinery responsible for this balance, and for the couplings themselves, is still poorly understood. This is because the couplings are highly sensitive to intermolecular distances. As a result of this sensitivity, the light-harvesting properties vary drastically among individual PPCs, because of small differences in protein conformation, and vary drastically even within a single PPC over time, because of protein fluctuations (2). In ensemble measurements, these drastic variations appear solely as a static, average value. Therefore, only through single-molecule spectroscopy can we investigate the photodynamics of individual PPCs, specifically how the absorption, energy transport, and dissipation of each change with time. We ...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Single-molecule spectroscopy reveals photosynthetic LH2 complexes switch between emissive states

Schlau‐Cohen¹,

Wang

Southall

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

126

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“…61,62 Two techniques that might offer particular promise for the deposition and tailoring of the molecular components in each active layer are dip-pen nanolithography and thermochemical nanolithography, in each of which the potential to order and chemically modify molecular units has recently been established. [63][64][65][66] In terms of applications, the achievement of optical switching in an extensive parallel-processing unit introduces a number of potential applications, beyond simple switching. Logic gate construction is an obvious possibility; the responsiveness to input modulation suggests other forms of action, possibly leading to optical transistor configurations.…”

Section: Discussionmentioning

confidence: 99%

Optically controlled resonance energy transfer: Mechanism and configuration for all-optical switching

Bradshaw

Andrews

2008

The Journal of Chemical Physics

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In a molecular system of energy donors and acceptors, resonance energy transfer is the primary mechanism by means of which electronic energy is redistributed between molecules, following the excitation of a donor. Given a suitable geometric configuration it is possible to completely inhibit this energy transfer in such a way that it can only be activated by application of an off-resonant laser beam: this is the principle of optically controlled resonance energy transfer, the basis for an all-optical switch. This paper begins with an investigation of optically controlled energy transfer between a single donor and acceptor molecule, identifying the symmetry and structural constraints and analyzing in detail the dependence on molecular energy level positioning. Spatially correlated donor and acceptor arrays with linear, square, and hexagonally structured arrangements are then assessed as potential configurations for all-optical switching. Built on quantum electrodynamical principles the concept of transfer fidelity, a parameter quantifying the efficiency of energy transportation, is introduced and defined. Results are explored by employing numerical simulations and graphical analysis. Finally, a discussion focuses on the advantages of such energy transfer based processes over all-optical switching of other proposed forms.

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“…Evolutionary competition at the organism level has driven photosynthetic subsystems toward optimal and robust function (Noy et al, 2006;Noy, 2008;Scholes et al, 2011) that can guide the design of artificial light harvesting devices such as biohybrid antennas (Harris et al, 2013) and nanopatterned light harvesting (LH) complex arrays (Reynolds et al, 2007;Vasilev et al, 2014;Patole et al, 2015). The development and improvement of such artificial, biological, or biohybrid light harvesting systems may alleviate mankind's future energy demand (Blankenship et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Overall energy conversion efficiency of a photosynthetic vesicle

Sener

Strümpfer

Singharoy

et al. 2016

eLife

174

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The chromatophore of purple bacteria is an intracellular spherical vesicle that exists in numerous copies in the cell and that efficiently converts sunlight into ATP synthesis, operating typically under low light conditions. Building on an atomic-level structural model of a low-lightadapted chromatophore vesicle from Rhodobacter sphaeroides, we investigate the cooperation between more than a hundred protein complexes in the vesicle. The steady-state ATP production rate as a function of incident light intensity is determined after identifying quinol turnover at the cytochrome bc 1 complex (cytbc 1 ) as rate limiting and assuming that the quinone/quinol pool of about 900 molecules acts in a quasi-stationary state. For an illumination condition equivalent to 1% of full sunlight, the vesicle exhibits an ATP production rate of 82 ATP molecules/s. The energy conversion efficiency of ATP synthesis at illuminations corresponding to 1%-5% of full sunlight is calculated to be 0.12-0.04, respectively. The vesicle stoichiometry, evolutionarily adapted to the low light intensities in the habitat of purple bacteria, is suboptimal for steady-state ATP turnover for the benefit of protection against over-illumination.

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Directed Formation of Micro- and Nanoscale Patterns of Functional Light-Harvesting LH2 Complexes

Cited by 54 publications

References 40 publications

Single-molecule spectroscopy reveals photosynthetic LH2 complexes switch between emissive states

Single-molecule spectroscopy reveals photosynthetic LH2 complexes switch between emissive states

Optically controlled resonance energy transfer: Mechanism and configuration for all-optical switching

Overall energy conversion efficiency of a photosynthetic vesicle

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