Limantara, Leenawaty and Fujii, Ritsuko and Zhang, Jian-Ping and Kakuno, Tomisaburo and Hara, Hideyuki and Kawamori, Asako and Yagura, Tatsuo and Cogdell, Richard J and Koyama, Yasushi (1998) Generation of Triplet and Cation-Radical Bacteriochlorophyll a in Carotenoidless LH1 and LH2 Antenna Complexes from Rhodobacter sphaeroides. Biochemistry, 35 (70). pp. 17469-17486.
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The LH1 antenna complex and a native form of the LH2 complex were isolated from the carotenoidless R26 and R26.1 mutants of Rhodobacter sphaeroides by the use of a new detergent, sucrose monocholate. One-color, pump-and-probe transient Raman spectroscopy of these complexes using 351 nm, ∼50 ps pulses showed the generation of the triplet state of bacteriochlorophyll a (BChl a), whereas measurements using 355 nm, ∼12 ns pulses showed the generation of BChl a cation radical. Subpicosecond to nanosecond time-resolved absorption spectroscopy using 388 nm, 200 fs pulses for excitation showed rapid (<1 ps) generation of the triplet state and fast decay (<10 ps) of the singlet state of BChl a. Microsecond absorption spectroscopy confirmed the generation of BChl a cation radical. EPR spectroscopy using 532 nm, ∼5 ns pulses for excitation established the generation of BChl a cation radical. The EPR line width suggested that the unpaired electron is shared by two BChl a molecules. In LH1, the yield of BChl a cation radical per complex was estimated to be about 80% of that in the reaction center, and in LH2 about 50%. Thus, rapid generation of the triplet state, and its subsequent transformation into the cation-radical state of BChl a have been shown to be intrinsic properties of B870 and B850 BChl a assembly in the carotenoidless LH1 and LH2 antenna complexes. In the case of the carotenoid-containing LH2 complex, the triplet states of BChl a and carotenoid (spheroidene) were generated immediately after excitation, but the triplet-state BChl a was quenched efficiently by the carotenoid so that no BChl a cation radical was generated. Thus, the photoprotective function of the carotenoid in this antenna complex is shown.
| Item Type: | Artikel |
|---|---|
| Subjects: | Q Science > QD Chemistry |
| Divisions: | Fakultas Teknologi dan Desain > Teknik Sipil |
| Depositing User: | Admin Repository |
| Date Deposited: | 15 Apr 2020 04:55 |
| Last Modified: | 03 Jun 2022 02:50 |
| URI: | http://eprints.upj.ac.id/id/eprint/83 |
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