Disordered Exciton Model for the Core Light-Harvesting Antenna of Rhodopseudomonas viridis

Novoderezhkin, Vladimir I.; Monshouwer, R.; Grondelle, Rienk van

doi:10.1016/s0006-3495(99)76922-5

Cited by 103 publications

(94 citation statements)

References 51 publications

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“…This means that we are not able to estimate the delocalization length from the shape of the pump-probe spectra only. On the other hand, we have also calculated the amplitude of the bleaching peak of the pump-probe spectra normalized to the bleaching of the BChl monomer 17 and we found that this relative bleaching value was varying from 5.4 to 11.2 in close correlation with the N eff value. So, the amplitude of the difference absorption contains information that can be used for a more precise estimation of the delocalization parameters.…”

Section: Introductionmentioning

confidence: 84%

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Exciton (De)Localization in the LH2 Antenna of Rhodobacter sphaeroides As Revealed by Relative Difference Absorption Measurements of the LH2 Antenna and the B820 Subunit

1999

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We report the results of relative difference absorption measurements for the LH2 antenna of Rhodobacter sphaeroides and the B820 subunit of Rhodospirillum rubrum at room temperature. It is shown that significant differences between shapes and amplitudes of photoinduced, absorption changes reflect a different degree of exciton delocalization in the intact antenna compared with the dimeric subunit. Using the exciton model in the presence of static disorder, we have obtained a consistent and quantitative fit of the amplitudes and shapes of the pump-probe spectra of the LH2 antenna and the B820 subunit. We estimate that the nearest-neighbors interaction energy in the antenna is about 400 cm -1 and the diagonal disorder is about 450 cm -1 . For these values the coherence length (FWHM) of the steady-state exciton wavepacket corresponds to 5 BChl molecules at room temperature. The amplitude of the difference absorption reflects a cooperative behavior within at least 12 BChls of the B850 antenna. The calculations suggest that the dimeric subunit is characterized by a decrease of the interaction energy to 300 cm -1 together with an increase of the disorder value to about 600 cm -1 .

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Section: Introductionmentioning

confidence: 84%

“…If we switch on the disorder, these values will be even smaller. Thus, modeling of the LH1 and LH2 antennas with the presence of static disorder gave the values N eff ) 5-11 6,8,17,21,30 and N coh ) 4-6 17,21,25 at room temperature. In all these models the exciton-phonon coupling was supposed to be weak.…”

Section: Introductionmentioning

confidence: 97%

Exciton (De)Localization in the LH2 Antenna of Rhodobacter sphaeroides As Revealed by Relative Difference Absorption Measurements of the LH2 Antenna and the B820 Subunit

1999

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“…All RP- † A similar analysis to determine the exciton delocalization length in bacterial lightharvesting antenna systems was applied in ref. 37. HPLC-purified oligodeoxynucleotides were purchased from Midland Certified Reagent Company (Midland, TX).…”

Section: Methodsmentioning

confidence: 99%

Electronic energy delocalization and dissipation in single- and double-stranded DNA

Buchvarov

Wang

Raytchev

et al. 2007

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

172

254

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The mechanism that nature applies to dissipate excess energy from solar UV light absorption in DNA is fundamental, because its efficiency determines the vulnerability of all genetic material to photodamage and subsequent mutations. Using femtosecond time-resolved broadband spectroscopy, we have traced the electronic excitation in both time and space along the base stack in a series of single-stranded and double-stranded DNA oligonucleotides. The obtained results demonstrate not only the presence of delocalized electronic domains (excitons) as a result of UV light absorption, but also reveal the spatial extent of the excitons.excitons ͉ femtosecond ͉ spectroscopy ͉ photophysics S ince the early days of DNA photochemistry there has been considerable speculation about the nature of the excited singlet states of the bases, i.e., whether they are localized on a single base or delocalized over several bases (1-4). The answer to this question is paramount for understanding the mechanism of UV light-induced chemical reactions that may result in carcinogenic mutations (5-7). Although the rich photochemistry of nucleic acids has been extensively studied (5, 6), the precursor states for chemical reactions damaging the genome are not well characterized. In other words, the nature of these states and the concomitant electronic and nuclear dynamics must be investigated to understand how excitation energy is transformed and dissipated within the double-helix. With respect to the biological consequences of UV light-induced phenomena in DNA most efforts were spent on the investigation of charge migration processes through the base stack (8, 9). Although photoinduced charge transfer is initiated by electronic excitation, no clear picture has yet emerged of how to describe electronic excitations in DNA. Circular dichroism measurements on single-stranded homoadenines and A⅐T duplexes indicate significant electronic coupling between the adjacent bases in the stack (10). On the other hand, the fact that the DNA UV spectra closely resemble the sum of the spectra of the constituent bases was interpreted as evidence for strictly localized excited states (1). Since the pioneering work of Eisinger et al. (2), who reported a broad red-shifted emission in high-concentrated nucleoside solutions at low temperatures, excimers and exciplexes have been invoked in discussions on nucleic acid (11-17). What remains unclear, however, is the question of whether these states are formed as a result of dynamic quenching, i.e., through combined nuclear rearrangements of locally excited bases with nonexcited adjacent bases. Alternatively, the UV excitation of DNA could have excitonic character with shared oscillator strength between adjacent bases. In this article, we provide firm experimental results that indicate the presence of electronically delocalized domains in DNA base stacks as a result of UV light absorption. Our femtosecond spectroscopic data are interpreted and discussed in the framework of molecular exciton theory (18). The first theoretical ...

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“…Excitons can extend over multiple chromophores [30][31][32] and can have a profound impact on the electronic structure and hence optical properties of the system as well as on energy transfer dynamics. Clear examples of excitons have been discovered in ensemble-averaged linear and nonlinear spectroscopy experiments [31][32][33][34][35][36][37][38][39] as well as single-molecule spectroscopy of LH2 from purple photosynthetic bacteria [40,41]. The latter have provided strong evidence for delocalized excited states immediately after the excitation of a single LH2.…”

Section: Energy Transfer and The Question Of Coherencementioning

confidence: 99%

Photosynthetic light harvesting: excitons and coherence

Fassioli

Dinshaw

Arpin

et al. 2014

J. R. Soc. Interface.

262

297

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Photosynthesis begins with light harvesting, where specialized pigmentprotein complexes transform sunlight into electronic excitations delivered to reaction centres to initiate charge separation. There is evidence that quantum coherence between electronic excited states plays a role in energy transfer. In this review, we discuss how quantum coherence manifests in photosynthetic light harvesting and its implications. We begin by examining the concept of an exciton, an excited electronic state delocalized over several spatially separated molecules, which is the most widely available signature of quantum coherence in light harvesting. We then discuss recent results concerning the possibility that quantum coherence between electronically excited states of donors and acceptors may give rise to a quantum coherent evolution of excitations, modifying the traditional incoherent picture of energy transfer. Key to this (partially) coherent energy transfer appears to be the structure of the environment, in particular the participation of non-equilibrium vibrational modes. We discuss the open questions and controversies regarding quantum coherent energy transfer and how these can be addressed using new experimental techniques.

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Disordered Exciton Model for the Core Light-Harvesting Antenna of Rhodopseudomonas viridis

Cited by 103 publications

References 51 publications

Exciton (De)Localization in the LH2 Antenna of Rhodobacter sphaeroides As Revealed by Relative Difference Absorption Measurements of the LH2 Antenna and the B820 Subunit

Exciton (De)Localization in the LH2 Antenna of Rhodobacter sphaeroides As Revealed by Relative Difference Absorption Measurements of the LH2 Antenna and the B820 Subunit

Electronic energy delocalization and dissipation in single- and double-stranded DNA

Photosynthetic light harvesting: excitons and coherence

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