|Budget Amount *help
¥8,800,000 (Direct Cost : ¥8,800,000)
Fiscal Year 1997 : ¥2,200,000 (Direct Cost : ¥2,200,000)
Fiscal Year 1996 : ¥6,600,000 (Direct Cost : ¥6,600,000)
Photosynthetic Reaction creates a large amount of energy on earth, which is basically of importance in the origin of life activity and of the human industrial activities. In this project, in order to clarify theoretically the photosynthetic reaction mechanism, we first studied the ground and excited states of various porphyrin compounds and of the socalled special pair which is in the photosynthetic reaction center, and then we studied the electron-transfer mechanism in the photosynthetic reaction center involving the effects of the surrounding proteins and aminoacids.
First, we studied the ground and low-lying excited states of various porphyrin compounds including magnesium porphin, free base tetrazaporphin, free base phthalocyanine, oxyheme, carboxy-heme, horse radish peroxie CO,free-base Chlorin, free base bacteriochlorin, pheophytin and chlorophyll. The SAC-CI calculations accurately reproduced the spectra of these compounds. We presented some new theoreticallassignments, and explained the origin of the trends in these spectra. These results were important and necessary for the next step of our project.
Next, we studied the excitation spectrum of the whole photosynthetic reaction center, and the electron transfer mechanism in the photosynthetic reaction center. We calculated all elements in the photosynthetic reaction center and assigned the spectrum theoretically. The effect of the surrounding proteins and aminoacids was considered applying the electrostatic field reproduced by the point charges. As a whole our result reasonably reproduced the spectrum of the photosynthetic reaction center. We found that the protein effect makes some absorption band shift to the red region. Next we calculated the electron transfer integrals which determine the electron transfer rate constants. Our results reproduced the L-branch selectivity observed in the photosynthetic reaction center.