B-side Electron Transfer in Bacterial Photosynthetic Reaction Centers Revealed by a Few-Cycle Pulse Laser

Juan Du ,Takayoshi Kobayashi ,Keiji Watanabe ,Hitoshi Tamiaki

doi:10.1051/epjconf/20134108012

Abstract

B-side electron transfer in wide-type reaction centers from Rhodobacter sphaeroides 2.4.1 was investigated by broadband real-time vibrational spectroscopy. HB − was found to be generated in less than 50 fs after the excitation of 6.3 fs laser pulse, and its decay lifetime was determined to be ~280fs and 1.4ps, which is extremely fast compared with the one occurring in A-side. Considering the ultrafast of the generation time of HB − , BB rather than P was found to be the initial electron donor to the H. Hence, the initial charge-separated state is determined to be BB + HB − state.

Highlights

The symmetric structure of the reaction center (RC) provides two possible electron-transfer pathways
B-side electron transfer in wide-type reaction centers from Rhodobacter sphaeroides 2.4.1 was investigated by broadband real-time vibrational spectroscopy
Electron transfer takes place from BBB to HBB in less than 50 fs, and decay components of the charge-separated BBB+HBB state are determined to be ~280fs and 1.4ps, which is extremely fast compared with the one occurring in A-side

Summary

Introduction

The symmetric structure of the reaction center (RC) provides two possible electron-transfer pathways. The functional asymmetry has been discovered and only the A-branch is active in charge transfer to form P+HAas the initial charge-separated state when the primary electron donor (P) is excited. The function of the B-branch cofactor is not yet clearly understood and only limited research result has been reported [1,2]. According to these previous studies, the B-branch function is very complicated and it electron transfer pathway is discovered to be dependent on the excitation wavelength, i.e. dependent on whether P or B (a monomer bacteriochlorophyll) or H (a bacteriopheophytin) is excited or to which excited state (Qy, Qx, or Soret band) they are excited. Electron transfer takes place from BBB to HBB in less than 50 fs, and decay components of the charge-separated BBB+HBB state are determined to be ~280fs and 1.4ps, which is extremely fast compared with the one occurring in A-side

Experimental method and material

Results and discussions

Conclusion