Ultrafast chlorophyllb‐chlorophyllaexcitation energy transfer in the isolated light harvesting complex, LHC II, of green plants

Publisher Website
Google Scholar
Abstract
The excitation energy transfer between chlorophyllb(Chlb) and chlorophylla(Chla) in the isolated trimeric chlorophyll‐a/b‐binding protein complex of spinach photosystem 2 (LHC II) has been studied by femtosecond spectroscopy. In the main absorption band of Chlbthe ground state recovery consists of two components of 0.5 ps and 2.0 ps, respectively. Also in the Chlaabsorption band, at 665 nm, the ground state recovery is essentially bi‐exponential. In this case is, however, the fastest relaxation lifetime is a 2.0 ps component followed by a slower component with a lifetime in the order of 10–20 ps. In the Chlbabsorption band a more or less constant anisotropy ofr= 0.2 was observed during the 3 ps the system was monitored. In the Chlaabsorption band there was, however, a relaxation of the anisiotropy fromr= 0.3 to a quasi steady state level ofr= 0.18 in about 1 ps. Since the 0.5 ps component is only seen upon selective excitation of Chlbwe assign this component to the energy transfer between Chlband Chla. The other components most likely represents redistribution processes of energy among spectrally different forms of Chla. The energy transfer process between Chlband Chlacan well be explained by the Förster mechanism which also gives a calculated distance of 13 Å between interacting chromophores. The organisation of chlorophylls in LHC II is discussed in view of the recent crystal structure data (1991) Nature 350, 130].

This publication has 26 references indexed in Scilit: