Primary photochemical processes in P700-enriched photosystem I particles: Trap-limited excitation decay and primary charge separation

Journal Article · Thu Oct 06 04:00:00 EDT 1994 · Journal of Physical Chemistry; (United States)

DOI:https://doi.org/10.1021/j100091a057· OSTI ID:6842177

Kumazaki, Shigeichi; Kandori, Hideki; Petek, Hrvoje; Yoshihara, Keitaro ^[1]; Ikegami, Isamu ^[2]

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1. Inst. for Molecular Science, Okazaki (Japan)
2. Teikyo Univ., Kanagawa (Japan)

The energy transfer and primary charge separation in photosystem I (PS I) reaction center (RC) particles with an antenna size of 12 chlorophyll/P700 were studied by subpicosecond transient absorption spectroscopy. Upon excitation of the particles at 638 nm under the donor chlorophyll (P700)-neutral conditions, the transition from the excited state of chlorophylls to the charge-separated state of P700[sup +]A[sub 0][sup [minus]] (A[sub 0]; acceptor chlorophyll [alpha]) proceeded with a time constant of 6.5 ps at [approximately]278 K. This time constant was obtained from the absorption increase of P700[sup +]A[sub 0][sup [minus]] at 740 ([+-]10) nm, where excited chlorophylls gave only a negligible absorbance change. The distribution of electronic excitation energy among different chlorophyll forms, which was monitored in the wavelength region 650-720 nm, did not show and significant change from 500 fs to 12 ps under both the P700-preoxidized and -neutral conditions. Comparison of the experimental distribution with simulated ones suggests that the excitation energy is distributed within 500 fs highly on P700 and also among other higher-energy chlorophyll forms. 55 refs., 9 figs.

• OSTI ID: 6842177
• Journal Information: Journal of Physical Chemistry; (United States), Journal Name: Journal of Physical Chemistry; (United States) Vol. 98:40; ISSN JPCHAX; ISSN 0022-3654
• Country of Publication: United States
• Language: English

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ABSORPTION SPECTROSCOPY
BOLTZMANN STATISTICS
CARBOXYLIC ACIDS
CHLOROPHYLL
ELECTRON TRANSFER
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ORGANIC COMPOUNDS
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PHOTOSYNTHETIC REACTION CENTERS
PHYTOCHROMES
PIGMENTS
PLANTS
PORPHYRINS
PROTEINS
SPECTROSCOPY
SPINACH
VEGETABLES