Picosecond absorption and circular dichroism studies of proteins

John Douglas Simon; Sunney Xie; Robert C. Dunn

doi:10.1117/12.44220

1 June 1991 Picosecond absorption and circular dichroism studies of proteins

John Douglas Simon, Sunney Xie, Robert C. Dunn

Proceedings Volume 1432, Biomolecular Spectroscopy II; (1991) https://doi.org/10.1117/12.44220
Event: Optics, Electro-Optics, and Laser Applications in Science and Engineering, 1991, Los Angeles, CA, United States

Abstract

Picosecond absorption and circular dichroism (CD) studies of photosynthetic reaction centers (RC) from Rhodabacter Sphaeroides are reported. The transient absorption spectra obtained are consistent with previous studies and provide definitive evidence for the formation of the two charge transfer intermediates: (BChl2)+BPhL-QA and (BChl2)+BPhLQA+ with rate constants whose half lives are <10 picosecond and $OM200 picoseconds, respectively. The transient circular dichroism spectra of these two charge separated intermediates are characterized by a nonconservative CD band centered at 800 nm with similar shape and intensity. This result clearly demonstrates that the negative CD band at 814 nm arises from the exciton coupling of the bacteriochlorophyll dimer. This transient CD cannot be due to excitonic interactions between the pigments in the reaction center and suggest that the monomer bacteriochlorophyll is either intrinsically chiral through distortions induced by the surrounding protein structure or obtains rotational strength from coupled oscillator interactions with surrounding aromatic residues in the protein.

Citation Download Citation

John Douglas Simon, Sunney Xie, and Robert C. Dunn "Picosecond absorption and circular dichroism studies of proteins", Proc. SPIE 1432, Biomolecular Spectroscopy II, (1 June 1991); https://doi.org/10.1117/12.44220

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