ИСТИНА

In order to determine the red chlorophylls location in the pigment-protein complex of the photosystem I (PSI) trimer, a simultaneous fit of the pump-probe kinetics and the linear spectra has been done. To create an exciton model of the energy transport in the PSI trimer, we used the available crystal structure and slightly modified it during the fit. The extended dipole-dipole approximation has been applied, to get the proper coupling energies between chlorophylls at distances less than 10 Å. Since more than 500 Chls have been taken into account for evaluation of the exciton dynamics, we optimized our computational routines and run them on a computer cluster using an optimization procedure known as the Differential evolution. To reproduce the pump-probe experimental data, which reveal the exciton transfer from antenna to the P700 reaction center with the rate of 40 ps at room temperature, it was assumed that the red exciton states directly involved in the energy transport process. It was shown that the excited chlorophyll molecules, which correspond to the red exciton states, are localized on the peripheral part of the PSI monomer, particularly in the places of contacts of monomers in the trimer. The role of the red exciton states in PSI energy transport is discussed in details.