Energy Transfer in the LH 2 Complex of Rb. Sphaeroides and Rps. Acidophila Studied by Sub Picosecond Absorption Spectroscopy

Monshouwer, R.; Zarate, Iñaki Ortiz de; Mourik, Frank van; Picorel, Rafael; Cogdell, Richard J.; Grondelle, Rienk van

doi:10.1007/978-94-009-0173-5_18

Cited by 4 publications

(6 citation statements)

References 3 publications

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“…This low-temperature transfer time is in excellent agreement with the 1.26 ps transfer time obtained in a previous pump−probe measurement on the B800−850 complex of Rps. acidophila (strain 10050) at 803 nm and at the same temperature . It is also very similar to the transfer time in the LH2 complex of Rb.…”

Section: Discussionsupporting

confidence: 64%

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Energy Transfer and Exciton Annihilation in the B800−850 Antenna Complex of the Photosynthetic Purple Bacterium Rhodopseudomonas acidophila (Strain 10050). A Femtosecond Transient Absorption Study

1997

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Excitation energy transfer and exciton annihilation in the isolated B800−850 antenna complex from the purple bacterium Rhodopseudomans acidophila (strain 10050) were studied by one-color transient absorption experiments with a typical pulse length of 50 fs at room temperature and 77 K. The anisotropy kinetics observed within the B800 band are clearly wavelength dependent, indicating that the B800 ↔ B800 energy transfer or excitonic relaxation processes are wavelength dependent. The depolarization times found at room temperature were 400 fs at 790 nm, 820 fs at 800 nm, and 360 fs at 810 nm. A faster depolarization time of 240 fs was obtained at 801 nm at 77 K, which is suggested to originate from excitonic relaxation. Energy transfer from the B800 to the B850 occurs in ∼0.8 ps at room temperature and ∼1.30 ps at 77 K. The kinetics obtained within the B800 band were observed for the first time to exhibit a dramatic dependence on the excitation intensity. When the excitation intensity is higher than 1.09 × 1014 photons pulse-1 cm-2, the transient absorption kinetics after ∼3 ps are dominated by a long-lived bleaching. However, in contrast, a slowly recovering excited-state absorption was found to be dominant at lower pump intensities. This intensity dependence is attributed to the variation of the population distribution between the lowest and next higher lying excitonic levels of the B850 ring, a result of exciton annihilation in the lowest-state, following the rapid energy transfer from the B800 to the B850 band and subsequent fast excitonic relaxation within the excitonic manifold of the B850 ring. The time constant for this annihilation process was found to be ∼1 ps. Excitonic calculations indicate that several high-lying excitonic states show good spectral overlap with the B800 band, and thus, they could serve as excellent acceptors for the energy transfer from B800 to B850.

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Section: Discussionsupporting

confidence: 64%

“…sphaeroides. 22 The depolarization might also be a manifestation of excitonic relaxation. The wavelength dependent depolarization observed in the present work, however, indicates that the B800 T B800 transfer or the excitonic relaxation must be wavelength dependent.…”

Section: Discussionmentioning

confidence: 99%

Energy Transfer and Exciton Annihilation in the B800−850 Antenna Complex of the Photosynthetic Purple Bacterium Rhodopseudomonas acidophila (Strain 10050). A Femtosecond Transient Absorption Study

1997

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“…The B800 → 850 energy transfer time in LH2 of Rb. sphaeroides was found to be about 1 ps using “long” ∼10 ps pulses; − later a time constant of about 0.7 ps at room temperature was firmly established. , The B800 → B850 energy transfer rate is weakly temperature dependent; at 77 K the time constant was found to be about 1 ps and it slows down further at 4 K. − For other LH2s similar time constants were obtained. − The detailed discussion of this transfer step is in section 6. The B800 → B800 energy transfer time (see section 5) was more difficult to establish, a variety of studies put it in the 0.3−1 ps range for LH2 of Rb.…”

Section: Introductionmentioning

confidence: 79%

“…22,23 The B800 f B850 energy transfer rate is weakly temperature dependent; at 77 K the time constant was found to be about 1 ps 24 and it slows down further at 4 K. [25][26][27] For other LH2s similar time constants were obtained. [28][29][30][31][32][33][34][35] The detailed discussion of this transfer step is in section 6. The B800 f B800 energy transfer time (see section 5) was more difficult to establish, a variety of studies put it in the 0.3-1 ps range for LH2 of Rb.…”

Section: Introductionmentioning

confidence: 99%

Photosynthetic Light-Harvesting: Reconciling Dynamics and Structure of Purple Bacterial LH2 Reveals Function of Photosynthetic Unit

1999

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Great progress in the study of structure and dynamics of photosynthetic light-harvesting pigment−protein complexes has recently resulted in detailed understanding of the light-harvesting and light-conversion processes of photosynthesis. We review and discuss recent results on the elementary excitation transfer dynamics of the purple bacterial LH2 peripheral complex. When combining the information from the two LH2 structures that are now available with the experimental results obtained from steady-state spectroscopy, a variety of ultrafast techniques and computer simulations, a detailed understanding of the LH2 function is obtained. Dynamics relevant to the complete photosynthetic unit (PSU = LH2 + LH1 core + reaction center), as well as models of the PSU obtained on the basis of the LH2 structure, allow us to suggest how the characteristic structural features of LH2 and LH1 have been designed to optimize the overall light-harvesting and trapping process in the PSU.

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“…sphaeroides (including mutant LH2 complexes) and Rps. acidophila (Sundström et al 1986 ;Freiberg et al 1988 ;Shreve et al 1991 ;Hess et al 1993Hess et al , 1994Monshouwer et al 1995 ;Fowler et al 1997 ;Kennis et al 1997b ;Ma et al 1997 ;Pullerits et al 1997). In LH2 complexes from Rps.…”

Section: B800pb850mentioning

confidence: 99%

The architecture and function of the light-harvesting apparatus of purple bacteria: from single molecules to in vivo membranes

Cogdell

Gall

Köhler

2006

Quart. Rev. Biophys.

650

734

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This review describes the structures of the two major integral membrane pigment complexes, the RC-LH1 'core' and LH2 complexes, which together make up the light-harvesting system present in typical purple photosynthetic bacteria. The antenna complexes serve to absorb incident solar radiation and to transfer it to the reaction centres, where it is used to 'power' the photosynthetic redox reaction and ultimately leads to the synthesis of ATP. Our current understanding of the biosynthesis and assembly of the LH and RC complexes is described, with special emphasis on the roles of the newly described bacteriophytochromes. Using both the structural information and that obtained from a wide variety of biophysical techniques, the details of each of the different energy-transfer reactions that occur, between the absorption of a photon and the charge separation in the RC, are described. Special emphasis is given to show how the use of single-molecule spectroscopy has provided a more detailed understanding of the molecular mechanisms involved in the energy-transfer processes. We have tried, with the help of an Appendix, to make the details of the quantum mechanics that are required to appreciate these molecular mechanisms, accessible to mathematically illiterate biologists. The elegance of the purple bacterial light-harvesting system lies in the way in which it has cleverly exploited quantum mechanics.

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Energy Transfer in the LH 2 Complex of Rb. Sphaeroides and Rps. Acidophila Studied by Sub Picosecond Absorption Spectroscopy

Cited by 4 publications

References 3 publications

Energy Transfer and Exciton Annihilation in the B800−850 Antenna Complex of the Photosynthetic Purple Bacterium Rhodopseudomonas acidophila (Strain 10050). A Femtosecond Transient Absorption Study

Energy Transfer and Exciton Annihilation in the B800−850 Antenna Complex of the Photosynthetic Purple Bacterium Rhodopseudomonas acidophila (Strain 10050). A Femtosecond Transient Absorption Study

Photosynthetic Light-Harvesting: Reconciling Dynamics and Structure of Purple Bacterial LH2 Reveals Function of Photosynthetic Unit

The architecture and function of the light-harvesting apparatus of purple bacteria: from single molecules to in vivo membranes

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