PATHWAYS OF ENERGY-FLOW THROUGH THE LIGHT-HARVESTING ANTENNA OF THE PHOTOSYNTHETIC PURPLE BACTERIUM RHODOBACTER-SPHAEROIDES

被引:31
作者
ZHANG, FG [1 ]
VANGRONDELLE, R [1 ]
SUNDSTROM, V [1 ]
机构
[1] FREE UNIV AMSTERDAM,DEPT BIOPHYS,PHYS LAB,1007 MC AMSTERDAM,NETHERLANDS
关键词
D O I
10.1016/S0006-3495(92)81898-2
中图分类号
Q6 [生物物理学];
学科分类号
071011 ;
摘要
Using low intensity picosecond absorption spectroscopy with independently tunable excitation and probing infrared pulses, we have studied the pathways of energy transport through the light-harvesting antenna pigments of the photosynthetic purple bacterium Rhodobacter sphaeroides. From the observed excited-state rise time of the red-most pigment B896 as a function of excitation wavelength it is concluded that the B850 pigment of LH2 is spectrally heterogeneous. For excitations originating in the B850 pigment this results in a fast channel (9 ps) that is mainly excited in the peak of the B850 absorption band, and a slow channel (35 ps) that is predominantly excited at approximately 840 nm. Upon excitation of B800, more than 90% of the excitations follow the fast path. From the observed kinetics it is concluded that the majority of the LH2 --> LH1 energy transfer takes place within at most a few picoseconds. The rate-limiting step in the whole energy transfer sequence appears to be the B896 --> reaction center transfer. The origin of the B850 heterogeneity and the slow 35-ps component is at the moment unclear. Possibly it represents a highly extended form of LH2 in which transfer to LH1 takes a relatively long time, due to a large number of transfer steps.
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页码:911 / 920
页数:10
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