The Electronically Excited States of LH2 Complexes from Rhodopseudomonas acidophila Strain 10050 Studied by Time-Resolved Spectroscopy and Dynamic Monte Carlo Simulations. II. Homo-Arrays Of LH2 Complexes Reconstituted Into Phospholipid Model Membranes

Pflock, Tobias J.; Oellerich, Silke; Krapf, Lisa; Southall, June; Cogdell, Richard J.; Ullmann, G. Matthias; Köhler, Jürgen

doi:10.1021/jp2023583

Cited by 28 publications

(35 citation statements)

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“…This lifetime reduction can partly be attributed to the short distance (6 nm) between the emitter and the antenna, allowing for quenching by non-resonant energy transfer to gold. 24,25 Also immobilization of the complex 47,48 and possibly singlet-singlet or singlet-triplet annihilation in LH2 49,50 can shorten the fluorescence lifetime. Finally, the L = 110 nm and L = 220 nm antennae are not completely out of resonance with the LH2 emission, as is particularly clear for the 220 nm NR for which the emission is still partly polarized along the antenna axis (Fig.…”

Section: Resonant Enhancement Of the Radiative And Non-radiative Decamentioning

confidence: 99%

Nanoantenna enhanced emission of light-harvesting complex 2: the role of resonance, polarization, and radiative and non-radiative rates

Wientjes

Renger

Curto

et al. 2014

Phys. Chem. Chem. Phys.

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Nanoantennae show potential for photosynthesis research for two reasons; first by spatially confining light for experiments which require high spatial resolution, and second by enhancing the photon emission of single light-harvesting complexes. For effective use of nanoantennae a detailed understanding of the interaction between the nanoantenna and the light-harvesting complex is required.Here we report how the excitation and emission of multiple purple bacterial LH2s (light-harvesting complex 2) are controlled by single gold nanorod antennae. LH2 complexes were chemically attached to such antennae, and the antenna length was systematically varied to tune the resonance with respect to the LH2 absorption and emission. There are three main findings. (i) The polarization of the LH2 emission is fully controlled by the resonant nanoantenna. (ii) The largest fluorescence enhancement, of 23 times, is reached for excitation with light at l = 850 nm, polarized along the long antenna-axis of the resonant antenna. The excitation enhancement is found to be 6 times, while the emission efficiency is increased 3.6 times. (iii) The fluorescence lifetime of LH2 depends strongly on the antenna length, with shortest lifetimes of B40 ps for the resonant antenna. The lifetime shortening arises from an 11 times resonant enhancement of the radiative rate, together with a 2-3 times increase of the non-radiative rate, compared to the off-resonant antenna. The observed length dependence of radiative and non-radiative rate enhancement is in good agreement with simulations. Overall this work gives a complete picture of how the excitation and emission of multi-pigment light-harvesting complexes are influenced by a dipole nanoantenna.

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Section: Resonant Enhancement Of the Radiative And Non-radiative Decamentioning

confidence: 99%

Nanoantenna enhanced emission of light-harvesting complex 2: the role of resonance, polarization, and radiative and non-radiative rates

Wientjes

Renger

Curto

et al. 2014

Phys. Chem. Chem. Phys.

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“…69,70 However, in those samples the possible intercomplex energy transfer increases the probability by orders of magnitude so that a LH complex receives a second excitation. 63 Although the highest fluence used in our work is close to the threshold given above, we rule out the possibility for SSA, because we work at nM concentrations, which excludes populating the |2 LH ⟩ state by intercomplex energy transfer. From the |2 LH ⟩ state the system can decay back to the ground state or cross over within 10 ns to the triplet state | 3 B875*, 1 Car⟩ which is quenched by the carotenoids with a rate of (10 ns) −1 71 resulting in the state |3 LH ⟩ = | 1 B875, 3 Car*⟩.…”

Section: ■ Results and Discussionmentioning

confidence: 93%

“…62,63 The LH1 ring in the various states is represented by colored spheres that are connected by transitions that have specific rates k ij . A LH1 ring in the electronic ground state is represented by a green sphere.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…62 Moreover, using these results as input for the interpretation of the transients obtained on reconstituted homo-arrays of LH2 complexes, i.e., model membranes of well-defined composition, we revealed a clear influence of the size and the geometry of the LH2 clusters on the fluorescence transients. 63 Here we present a study on the time-resolved emission from isolated RC-LH1 complexes from the species Rps. palustris, where we have systematically varied the photon fluence, the repetition rate of the excitation laser, and the concentrations of a reducing and an oxidizing agent.…”

Section: ■ Introductionmentioning

confidence: 99%

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The Open, the Closed, and the Empty: Time-Resolved Fluorescence Spectroscopy and Computational Analysis of RC-LH1 Complexes from Rhodopseudomonas palustris

et al. 2015

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ABSTRACT:We studied the time-resolved fluorescence of isolated RC-LH1 complexes from Rhodopseudomonas palustris as a function of the photon fluence and the repetition rate of the excitation laser. Both parameters were varied systematically over 3 orders of magnitude. On the basis of a microstate description we developed a quantitative model for RC-LH1 and obtained very good agreement between experiments and elaborate simulations based on a global master equation approach. The model allows us to predict the relative population of RC-LH1 complexes with the special pair in the neutral state or in the oxidized state P + and those complexes that lack a reaction center. ■ INTRODUCTIONPhotosynthetic purple bacteria have evolved a wonderful modular principle for the light-harvesting (LH) apparatus that captures the solar radiation. These modules consist of pairs of hydrophobic, low molecular weight polypeptides that noncovalently bind a small number of bacteriochlorophyll (Bchl a) and carotenoid (Car) molecules and that self-assemble to produce the native pigment−protein complexes. 1−6 Most purple bacteria have two main types of complexes, the core complex, RC-LH1, and the peripheral complex, LH2. In the photosynthetic membrane the LH2 complexes are arranged in a two-dimensional network around the perimeter of the RC-LH1 complexes and the light energy absorbed by LH2 is transferred via LH1 to the reaction center (RC) where it is used to separate charge across the membrane. 7 For many years, high-resolution structural information has been available for the RC, 8−11 and the peripheral light-harvesting complexes 1−3 for a couple of species, whereas the first higher-resolution X-ray structure for a RC-LH1 complex has been determined only recently. 6 The current view is that there are at least two distinct classes of RC-LH1 complexes: Those that are monomeric, i.e., consisting of one RC surrounded by one LH1 complex, and those that are dimeric. 12,13 For RC-LH1 from Rps. palustris exists a lowresolution X-ray structure. 4 Accordingly, the RC is enclosed by an overall elliptically shaped LH1 consisting of 15 αβ-subunits that feature a gap, which is also consistent with data from optical single-molecule experiments. 14,15 Each subunit accommodates two light harvesting BChl a molecules giving rise to an absorption band at 875 nm. The reaction center complex accommodates a BChl a dimer (special pair, primary donor, P), two accessory BChl a molecules (B A , B B ), two bacteriopheophytin a (BPheo a) molecules (H A , H B ), and two ubiquinones (Q A , Q B ) bound to two protein subunits denoted L and M. The cofactors are arranged in two nearly identical branches, called A and B, which share the primary donor, P. 9,11,16,17 In particular the RC from Rhodobacter (Rb.) sphaeroides has served as a cornerstone for elucidating structure−function relationships employing a large variety of spin resonance 18−23 and optical spectroscopies. 24−31 From these studies it is well established that in the RC the absorbed photon-energy is used to dri...

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“…An important observation is that well-ordered hexagonal domains occur for both octameric and nonameric structures, suggesting that a close packing order is preferable to a crystalline order. Understanding the symmetry properties on the level of both the individual complex and the supramolecular complex is necessary to form a complete picture of efficient excitation energy transfer in the light-harvesting antenna (18,19) and has direct implications for the design of efficient synthetic devices (20)(21)(22)(23)(24)(25)(26).In this work, we investigate the role of fold symmetry in promoting excitation energy transfer in LH2 hexagonal domains, using an N-fold model geometry of a B850 ring based on the αβ-heterodimer subunit of Rps. acidophila (outlined in SI Materials and Methods, Fig.…”

mentioning

confidence: 99%

Optimal fold symmetry of LH2 rings on a photosynthetic membrane

Cleary

Chen

Chuang

et al. 2013

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

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An intriguing observation of photosynthetic light-harvesting systems is the N-fold symmetry of light-harvesting complex 2 (LH2) of purple bacteria. We calculate the optimal rotational configuration of N-fold rings on a hexagonal lattice and establish two related mechanisms for the promotion of maximum excitation energy transfer (EET). (i) For certain fold numbers, there exist optimal basis cells with rotational symmetry, extendable to the entire lattice for the global optimization of the EET network. (ii) The type of basis cell can reduce or remove the frustration of EET rates across the photosynthetic network. We find that the existence of a basis cell and its type are directly related to the number of matching points S between the fold symmetry and the hexagonal lattice. The two complementary mechanisms provide selection criteria for the fold number and identify groups of consecutive numbers. Remarkably, one such group consists of the naturally occurring 8-, 9-, and 10-fold rings. By considering the inter-ring distance and EET rate, we demonstrate that this group can achieve minimal rotational sensitivity in addition to an optimal packing density, achieving robust and efficient EET. This corroborates our findings i and ii and, through their direct relation to S, suggests the design principle of matching the internal symmetry with the lattice order.P hotosynthesis lies at the heart of all life on the planet. Excitation energy created in a peripheral light-harvesting antenna complex, upon absorption of a photon, is efficiently transferred via an exciton mechanism, sometimes over hundreds of angstroms, to a reaction center where charge separation takes place, creating a transmembrane electrochemical potential difference that ultimately drives the production of ATP. Light-harvesting antenna complexes, whose primary function is to increase the effective crosssection for photon absorption, while maintaining an efficient energy transfer network, consist of well-ordered membrane-associated arrays of light-absorbing pigments, namely chlorophyll or bacterichlorophyll (BChl), embedded in a protein environment (1-4).Perhaps the most intriguing aspect of light-harvesting systems is the N-fold symmetry displayed by light-harvesting complex 2 (LH2) of purple nonsulfur bacteria. Fold symmetry occurs in systems as diverse as carbon nanotubes, tubular dye aggregates, and the mosaic virus protein, as well as in snow flakes, tori, and nonperiodic tilings (5). In LH2, the N-fold symmetry arises from the N repetitions of a basic heterodimer subunit consisting of two transmembrane polypeptides, α and β, arranged in a circular structure (6-8). Each αβ-heterodimer subunit noncovalently binds one B800 BChl and two B850 BChls (Fig. 1A), so named according to their respective room-temperature absorption bands in the infrared region of the spectrum. In most bacterial species, the αβ-heterodimer repeats eight or nine times to form an octameric or nonameric ring structure (in Rhodopseudomonas paulisterium 10-fold rings have also been observ...

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The Electronically Excited States of LH2 Complexes from Rhodopseudomonas acidophila Strain 10050 Studied by Time-Resolved Spectroscopy and Dynamic Monte Carlo Simulations. II. Homo-Arrays Of LH2 Complexes Reconstituted Into Phospholipid Model Membranes

Cited by 28 publications

References 54 publications

Nanoantenna enhanced emission of light-harvesting complex 2: the role of resonance, polarization, and radiative and non-radiative rates

Nanoantenna enhanced emission of light-harvesting complex 2: the role of resonance, polarization, and radiative and non-radiative rates

The Open, the Closed, and the Empty: Time-Resolved Fluorescence Spectroscopy and Computational Analysis of RC-LH1 Complexes from Rhodopseudomonas palustris

Optimal fold symmetry of LH2 rings on a photosynthetic membrane

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