A Permanent Hole Burning Study of the FMO Antenna Complex of the Green Sulfur Bacterium Prosthecochloris aestuarii

• Published in: Biochemistry (Easton) Vol. 37; no. 15; pp. 5046 - 5051
• Main Authors: Franken, Eric M, Neerken, Sieglinde, Louwe, Rob J. W, Amesz, Jan, Aartsma, Thijs J
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 14-04-1998
• Subjects: Bacterial Proteins; Chlorobi - radiation effects; Dose-Response Relationship, Radiation; Energy Transfer; Infrared Rays; Lasers; Light-Harvesting Protein Complexes; Photosynthetic Reaction Center Complex Proteins - radiation effects; Protein Conformation; Spectrophotometry, Infrared
• DOI: 10.1021/bi972264c
• EISSN: 1520-4995
• ISSN: 0006-2960

A permanent hole burning study on the Fenna−Matthews−Olson, or FMO, antenna complex of the green sulfur bacterium Prosthecochloris aestuarii was carried out at 6 K. Excitation resulted not only in relatively sharp features resonant with the burn wavelength but also in broad absorbance changes in the wavelength region of 800−820 nm. The shape of the latter changes was almost independent of the wavelength of excitation. Evidence is given that they are induced by a different mechanism than that which causes the resonant holes and that they may be due to a conformational change of the protein. The original spectrum was restored upon warming to 60 K. The effective dephasing times T 2, as obtained from the homogeneous line widths, increased from about 0.5 ps at 803 nm to ≥20 ps at 830 nm and are in good agreement with recent measurements of accumulated photon-echo and time-resolved absorbance changes.