Ultrafast Photophysical Properties of Light-harvesting Complexes (LH2) in Purple Bacteria
紫细菌捕光天线LH2中的超快光物理研究

The ultrafast photophysical processes in light-harvesting complex LH2 in purple bacteria are investigated by using femtosecond pump-probe technique.With the excitation wavelength at blue side of B800 absorption band,a hundred of femtosecond decay component is observed,which can be ascribed to the energy transfer from B800 to B850.The obtained result is not consistent with the Frster energy mechanism,which implies there is an additional energy transfer process via upper exciton band of B850.Under the excitation wavelength at red side of B800 absorption band,there is a fast excited state absorption before photo-bleaching,originating from the direct excitation of upper excitonic levels of B850 molecules.From the kinetic traces of RS601 and GM309 with 800 nm excitation,the energy transfer from B800 to B850 is slow down in GM309.With 845 nm excitation,the energy redistribution in excited state of B850 in GM309 is faster than that in RS601.These results indicate the structural change of carotenoid affects the excitation relaxation of pigments and energy transfer between in LH2.