Picosecond Infrared Spectroscopy of the Photosynthetic Reaction Center

We report the first picosecond infrared spectroscopic study on the reaction center of bacterial photosynthesis. Infrared difference spectra in the range from 1560 to 1800 cm−1 were recorded and investigated from 50 ps to 4 ns.after photooxidation of the primary donor. Bands at 1755, 1707 and 1683 cm−1 can be assigned to vibrations of cofactor carbonyl groups. Protein contributions at 1644, 1661 and 1665 cm−1 (amide I) and at 1727 cm−1 (carboxylic residues) and their kinetics reflect the fast protein response to intermolecular charge transfer.