Ultrafast energy transfer in LHC-II revealed by three-pulse photon echo peak shift measurements

被引:97
作者
Agarwal, R
Krueger, BP
Scholes, GD
Yang, M
Yom, J
Mets, L
Fleming, GR [1 ]
机构
[1] Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA
[2] Univ Calif Berkeley, Lawrence Berkeley Lab, Phys Biosci Div, Berkeley, CA 94720 USA
[3] Univ Chicago, Dept Mol Genet & Cell Biol, Chicago, IL 60637 USA
来源
JOURNAL OF PHYSICAL CHEMISTRY B | 2000年 / 104卷 / 13期
关键词
D O I
10.1021/jp9915578
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
We report the results of three-pulse photon echo peak shift (3PEPS) measurements on the light-harvesting complex II (LHC-II) of the green algae Chlamydomonas reinhardtii. Experiments were performed at two different excitation wavelengths, 670 and 650 nm. corresponding to Chi-a and Chl-b excitation, respectively, The 3PEPS data are analyzed using a new theory that incorporates the effect of energy transfer on third-order response functions. Our theoretical model separates energy transfer dynamics from the solvation dynamics arising from coupling of the electronic transitions to the protein environment. We suggest that the protein fluctuations can be described by an ultrafast solvation on a sub-100 fs time scale and a long time correlation (static disorder). Decay of the 670 nm peak shift reveals spectral equilibration time scales for Chl-rr molecules that range from 300 fs to 6 ps and agree well with other experiments. 3PEPS data at 650 nm (Chl-b excitation) reveal rapid Chl-b to Chl-b energy transfer (<1 ps), which suggests excitation hopping between a pair of Chls-b, and slow energy transfer from these Chls-b to Chls-a. Also, a 60 cm(-1) oscillatory mode is observed for Chl-b which we attribute to the first observation of coherent nuclear dynamics in LHC-II. Calculating the energy transfer dynamics based on recently proposed assignments of chromophores by solving the master equation reveals Chl-b intra- and interband energy transfer dynamics that are in qualitative agreement with the simulation model of the peak shift data.
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页码:2908 / 2918
页数:11
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