B800→B850 energy transfer mechanism in bacterial LH2 complexes investigated by B800 pigment exchange

被引:125
作者
Herek, JL
Fraser, NJ
Pullerits, T
Martinsson, P
Polivka, T
Scheer, H
Cogdell, RJ
Sundström, V
机构
[1] Lund Univ, Dept Chem Phys, S-22100 Lund, Sweden
[2] Univ Glasgow, IBLS, Div Biochem & Mol Biol, Glasgow G12 8QQ, Lanark, Scotland
[3] Univ Munich, Inst Bot, D-80638 Munich, Germany
基金
英国生物技术与生命科学研究理事会;
关键词
D O I
10.1016/S0006-3495(00)76803-2
中图分类号
Q6 [生物物理学];
学科分类号
071011 ;
摘要
Femtosecond transient absorption measurements were performed on native and a series of reconstituted LH2 complexes from Rhodopseudomonas acidophila 10050 at room temperature. The reconstituted complexes contain chemically modified tetrapyrrole pigments in place of the native bacteriochlorophyll a-B800 molecules. The spectral characteristics of the modified pigments vary significantly, such that within the B800 binding sites the BB00 Q(y) absorption maximum can be shifted incrementally from 800 to 670 nm. As the spectral overlap between the 8800 and B850 Q(y) bands decreases, the rate of energy transfer las determined by the time-dependent bleaching of the B850 absorption band) also decreases; the measured time constants range from 0.9 ps (bacteriochlorophyll a in the 8800 sites, Q(y) absorption maximum at 800 nm) to 8.3 ps (chlorophyll a in the B800 sites, Q(y) absorption maximum at 670 nm). This correlation between energy transfer rate and spectral blue-shift of the B800 absorption band is in qualitative agreement with the trend predicted from Forster spectral overlap calculations, although the experimentally determined rates are similar to 5 times faster than those predicted by simulations. This discrepancy is attributed to an underestimation of the electronic coupling between the 8800 and B850 molecules.
引用
收藏
页码:2590 / 2596
页数:7
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