TY - JOUR
T1 - Ultrafast pump-probe spectroscopy of bacteriochlorophyll c antennae in bacteriochlorophyll a-containing chlorosomes from the green photosynthetic bacterium Chloroflexus aurantiacus
AU - Lin, Su
AU - Amerongen, Herbert Van
AU - Struve, Walter S.
PY - 1991/9/27
Y1 - 1991/9/27
N2 - Time-dependent isotropic and anisotropic absorption difference profiles have been obtained with 2 ps resolution for the (BChl) bacteriochlorophyll c antenna in BChl a-containing chlorosomes from the green photosynthetic bacterium Chloroflexus aurantiacus. The isotropic absorption difference spectra are bipolar; they are dominated by excited state absorption at wavelengths < 725 nm, and by ground state photobleaching at wavelengths > 735 nm. The entire isotropic spectrum exhibits a dynamic blue shift over approx. 4 nm with a time constant of approx. 7 ps. All of these phenomena are rationalized in terms of a linear exciton model that resembles the theory of J-aggregates. In this theory, the occurrence of the dynamic blue shift corresponds to relaxation between Qy excitation components; it cannot readily be explained using a model that assumes that the excitations are localized on single chromophores within 1 ps. The anisotropic decay times, resolved here for the first time with our 2 ps fwhm instrument function, are approx. 7 ± 1 ps at 720 nm and 4 ± 1 ps at 740 nm. The residual anisotropy r(∞) is 0.32 ± 0.02 at 740 nm, which is in good agreement with fluorescence and linear dichroism measurements. These anisotropy functions initialize to 0.4 within error, indicating that subpicosecond depolarization is not prevalent.
AB - Time-dependent isotropic and anisotropic absorption difference profiles have been obtained with 2 ps resolution for the (BChl) bacteriochlorophyll c antenna in BChl a-containing chlorosomes from the green photosynthetic bacterium Chloroflexus aurantiacus. The isotropic absorption difference spectra are bipolar; they are dominated by excited state absorption at wavelengths < 725 nm, and by ground state photobleaching at wavelengths > 735 nm. The entire isotropic spectrum exhibits a dynamic blue shift over approx. 4 nm with a time constant of approx. 7 ps. All of these phenomena are rationalized in terms of a linear exciton model that resembles the theory of J-aggregates. In this theory, the occurrence of the dynamic blue shift corresponds to relaxation between Qy excitation components; it cannot readily be explained using a model that assumes that the excitations are localized on single chromophores within 1 ps. The anisotropic decay times, resolved here for the first time with our 2 ps fwhm instrument function, are approx. 7 ± 1 ps at 720 nm and 4 ± 1 ps at 740 nm. The residual anisotropy r(∞) is 0.32 ± 0.02 at 740 nm, which is in good agreement with fluorescence and linear dichroism measurements. These anisotropy functions initialize to 0.4 within error, indicating that subpicosecond depolarization is not prevalent.
KW - (C. aurantiacus)
KW - Antenna
KW - Bacterial photosynthesis
KW - Bacteriochlorophyll
KW - Chlorosome
KW - Pump-probe spectroscopy
KW - Ultrafast spectroscopy
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U2 - 10.1016/S0005-2728(05)80113-6
DO - 10.1016/S0005-2728(05)80113-6
M3 - Article
AN - SCOPUS:0025887313
VL - 1060
SP - 13
EP - 24
JO - Biochimica et Biophysica Acta - Bioenergetics
JF - Biochimica et Biophysica Acta - Bioenergetics
SN - 0005-2728
IS - 1
ER -