Spectroscopic evidence for triplet excitation energy transfer among carotenoids in the LH2 complex from photosynthetic bacterium Rhodopseudomonas palustris

  • Juan Feng
  • Qian Wang
  • Xujia Zhang
  • Youguo Huang
  • Xicheng Ai
  • Xingkang Zhang
  • Jianping Zhang


The LH2 complex from Rhodopsudomonas (Rps.) palustris is unique in the heterogeneous carotenoid compositions. The dynamics of triplet excited state Carotenoids (3Car* has been investigated by means of sub-microsecond time-resolved absorption spectroscopy both at physiological temperature (295 K) and at cryogenic temperature (77K). Broad and asymmetric T n ←T 1 transient absorption was observed at room temperature following the photo-excitation of Car at 532 nm, which suggests the contribution from various carotenoid compositions having different numbers of conjugated C=C double bonds (Nc=c). The triplet absorption bands of different carotenoids, which superimposed at room temperature, could be clearly distinguished upon decreasing the temperature down to 77 K. At room temperature the shorter-wavelength side of the main Tn04T1 absorption band decayed rapidly to reach a spectral equilibration with a characteristic time constant of ∽1 μs, the same spectral dynamics, however, was not observed at 77 K. The aforementioned spectral dynamics can be explained in terms of the triplet-excitation transfer among heterogeneous carotenoid compositions. Global spectral analysis was applied to the time-resolved spectra at room temperature, which revealed two spectral components peaked at 545 and 565 nm, and assignable to the Tn04 T1 absorption of Cars with Nc=c=11 and Nc=c=13, respectively. Surprisingly, the decay time constant of a shorter-conjugated Car, i.e. 0.72 ώs (aerobic) and 1.36 ώs (anaerobic), is smaller than that of a longer-conjugated Car, i.e. 2.12 us (aerobic) and 3.75 ώs (anaerobic), which is contradictory to the general rule of carotenoids and relative polyenes. The results are explained in terms of triplet-excitation transfer among different types of Cars. It is postulated that two Cars with different conjugation lengths coexist in an α, β-subunit in the LH2 complex.


purple photosynthetic bacteria carotenoid excited-state time-resolved spectroscopy 


  1. 1.
    McDermott, G., Prince, S. M., Freer, A. A. et al., Crystal structure of an integral membrane light-harvesting complex from photosynthetic bacteria, Nature, 1995,374: 517–521.CrossRefGoogle Scholar
  2. 2.
    Koepke, J., Hu, X., Muenke, C. et al., The crystal structure of the light-harvesting complex II (B800-850) from Rhodospirillum molischianum. Structure, 1996, 4(5): 581–597.CrossRefGoogle Scholar
  3. 3.
    He, Z., Sundström, V., Pullerits, T., Intermolecular hydrogen bonding between carotenoid and bacteriochlorophyll in LH2, FEBS Letters, 2001, 496: 36–39.CrossRefGoogle Scholar
  4. 4.
    Moruik, F. V., Hawthornthwaitem, A. M., Vonk, C. et al., Spectroscopic characterization of the low-light B800-850 light-harvesting complex of Rhodopseudomonas Palustris, strain 2.1.6, Biochim. Biophys. Acta, 1992, 1140: 85–93.Google Scholar
  5. 5.
    Nishimura, Y., Shimada, K., Yamazaki, I. et al., Energy transfer processes in Rhodopseudomonas Palustris grown under low-light conditions, FEBS Letters, 1993, 3 (29): 319–323.CrossRefGoogle Scholar
  6. 6.
    Gall, A., Robert, B., Characterization of the different peripheral light-harvesting complexes from high- and low-light grown cells from Rhodopseudomnononas Palustris, Biochemistry, 1999, 38: 5181–5190.CrossRefGoogle Scholar
  7. 7.
    Bose, S. K., Media for anaerobic growth of photosynthetic bacteria, in Bacterial Photosynthesis (eds. Gest, H., Pietro, A. S., Vernon, L. P.), Yellow Springs, OH: The Antioch Press, 1963.Google Scholar
  8. 8.
    Evans, M. B., Hawthornthwaite, A. M., Cogdell, R. J., Isolation and characterization of the different B800-850 light-harvesting complexes from low- and high-light grown cells of Rhodopseu domonas Palustris, strain 2.1.6, Biochim. Biophys. Acta, 1990, 1016:71–76.CrossRefGoogle Scholar
  9. 9.
    van Mourik, F., Hawthornthwaite, A. M., Vonk, C. et al., Spectroscopic characterization of the low-light B800-850 light-harvesting complex of Rhodopseudomonas Palustris, strain 2.1.6, Biochim. Biophys. Acta, 1992, 1140: 85–93.Google Scholar
  10. 10.
    Crystall, B., Booth, P. J., Klug, D. R. et al., Resolution of a long lived fluorescence component from Dl/D2/cytochrome b-559 reaction centers, FEBS Letters, 1989, 249 (1): 75–78.CrossRefGoogle Scholar
  11. 11.
    Hartigan, N., Tharia, H. A., Sweeney, F. et al., The 7.5-Å electron density and spectroscopic properties of a novel low-light B800 LH2 from Rhodopseudomonas Palustris, Biophys. J., 2002, 82 (2): 963–977.CrossRefGoogle Scholar
  12. 12.
    Tharia, H. A., Hawthornthwaitem, T. D., Vonk, C. et al., Characterization of hydrophobic peptides by Rp-HPLC from different spectral forms of LH2 isolated from Rps. Palustris, Photosynthesis Research, 1999,61: 157–167.CrossRefGoogle Scholar
  13. 13.
    Qian, P., Saiki, K., Mizoguchi, T. et al., Time-dependent changes in the carotenoid composition and preferential binding of spirilloxanthin to the reaction center and anhydrorhodovibrin to the LH1 antenna complex in Rhodobium marinum, Photochemistry and Photobiology, 2001, 74 (3): 444–452.CrossRefGoogle Scholar
  14. 14.
    Frank, H. A., Joseu, J. S., Bautista, J. A. et al., Spectroscopic and photochemical properties of open-chain carotenoids, J. Phys. Chem. B, 2002, 106 (8): 2083–2092.CrossRefGoogle Scholar
  15. 15.
    Frank, H. A., Bautista, J. A., Josue, J. et al., Effect of the solvent environment on the spectroscopic properties and dynamics of the lowest excited state of carotenoid, J. Phys. Chem. B, 2000, 104 (18): 4569–4577.CrossRefGoogle Scholar
  16. 16.
    Burke, M., Land, E. J., McGarvey, D. J. et al., Carotenoid triplet state lifetimes, Journal of Photochemistry and Photobiology B: Biology, 2000, 59: 132–138.CrossRefGoogle Scholar
  17. 17.
    Hofrichter, J., Henry, E. R., Sommer, J. H. et al., Nanosecond optical spectra of iron-cobalt hybrid hemoglobins: Geminate recombination, conformational changes, and intersubunit communication, Biochemistry, 1985, 24 (11): 2667–2679.CrossRefGoogle Scholar
  18. 18.
    Bittl, R., Schlodder, E., Geisenheimer, I. et al., Transient EPR and absorption studies of carotenoids triplet formation in purple bacterial antenna complexes, J. Phys. Chem. B, 2001, 105(23): 5525–5535.CrossRefGoogle Scholar
  19. 19.
    Rademaker, H., Hoff, A. J., Van Grondelle, R. et al., Carotenoid triplet yields in normal and deuterated Rhodospirillum Rubrum, Biochim. Biophys. Acta, 1980, 592: 240–257.CrossRefGoogle Scholar
  20. 20.
    Herek, J. L., Polivka, T., Pullerits, T. et al., Ultrafast carotenoid band shifts probe structure and dynamics in photosynthetic antenna complexes, Biochemistry, 1998,37(20): 7057–7061.CrossRefGoogle Scholar
  21. 21.
    Arellano, J. B., Bangar Raju, B., Razi Naqvi, K. et al., Estimation of pigment stoichiometries in photosynthetic systems of purple bacteria: special reference to the (absence of) second carotenoid in LH2, Photochemistry and Photobiology, 1998, 68 (1): 84–87.CrossRefGoogle Scholar
  22. 22.
    Papiz, M. Z., Prince, S. M., Howard, al., The structure and thermal motion of the B800-850 LH2 complex from Rps. acidophila at 2.0 A resolution and 100 K: New structural features and functionally relevant motions, J. Mol. Bio., 2003, 326: 1523–1538.CrossRefGoogle Scholar

Copyright information

© Science in China Press 2004

Authors and Affiliations

  • Juan Feng
    • 1
  • Qian Wang
    • 1
  • Xujia Zhang
    • 2
  • Youguo Huang
    • 2
  • Xicheng Ai
    • 1
  • Xingkang Zhang
    • 1
  • Jianping Zhang
    • 1
  1. 1.State Key Laboratory for Structural Chemistry of Unstable and Stable Species Institute of ChemistryChinese Academy of SciencesBeijingChina
  2. 2.National Laboratory of Biomacromolecules Institute of BiophysicsChinese Academy of SciencesBeijingChina

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