COMPUTER-SIMULATION ON KINETICS OF PRIMARY PROCESS IN PHOTOSYNTHESIS OF ALGAE .5. EXCITATION-ENERGY TRANSFER IN PHYCOERYTHROCYANINS

Excitation energy transfer in phycoerythrocyanins (PEC) was studied by use of computer simulation. The results observed from the simulation are as follows: (i) The alpha(84) is a more efficient sensitizing chro mophore than beta(155) and donates the excitation energy into beta(84) and beta(155) while it scarcely emits fluorescence itself. (ii) Only the 1 alpha(84)-->2 beta(84) is the sub-picosecond process in a PEC tr imer, therefore it is readily to obtain the time constant from fs-leve l time-resolved spectral measurement. (iii) The beta(84) and beta(155) chromophores in PEC behave quite differently from those in C-PC becau se of the changes in alpha(84). It is observed that 1 beta(155) --> 6 beta(155) is the dominant pathway linking two trimers and both of the chromophores possess much higher fluorescence fractions, and about 80% of the total fluorescence is emitted from the beta(84) chromophore. ( iv) A far less mean number of transfer times is observed through the f ast-transfer pairs in PEC compared with that in C-PC because of slow t ransfer rate for the path from 2 beta(84) --> 1 alpha(84). (v) Relativ ely, PEC could absorb and transfer excitation energy more efficiently than C-PC.