Abstract

The bacterial reaction center of Rhodobacter Sphaeroides contains six pigments, arranged within a protein environment. These pigments act in a very concerted way to generate a remarkably efficient charge transfer which initiates the process of photosynthesis.¹ The structure of the reaction center is well known, consisting of two strongly interacting bacteriochlorophyll (BChl) molecules known as the special pair (P), two accessory BChls, and two bacteriopheophytins (H) arranged in approximately C₂ symmetry.²,³,⁴ Upon excitation of P, either directly (light absorption) or through energy transfer from the light harvesting antennae, an electron is transferred to H within about 3 ps. Although much work has been done on these types of systems, many issues remain unresolved: (1) what is the role of the accessory bacteriochlorophyll (B) in the electron transfer, (2) what is the influence of the upper excitonic state of P (P_y+), (3) what is the spectrum of fluctuations (frequencies, couplings…) that describes the interaction of the reaction center chromophores with the protein environment?

© 1996 Optical Society of America