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Proceedings Paper

Picosecond absorption and circular dichroism studies of proteins
Author(s): John Douglas Simon; Sunney Xie; Robert C. Dunn
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Paper 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.

Paper Details

Date Published: 1 June 1991
PDF: 10 pages
Proc. SPIE 1432, Biomolecular Spectroscopy II, (1 June 1991); doi: 10.1117/12.44220
Show Author Affiliations
John Douglas Simon, Univ. of California/San Diego (United States)
Sunney Xie, Univ. of California/San Diego (United States)
Robert C. Dunn, Univ. of California/San Diego (United States)

Published in SPIE Proceedings Vol. 1432:
Biomolecular Spectroscopy II
Robert R. Birge; Laurence A. Nafie, Editor(s)

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