Functions and Structures of Environmentally Relevant Enzymes

Asako, Kawamori and Yusuke, Matsuda and Limantara, Leenawaty and Ritsuko, Fujii and Yasushi, Koyama (2000) Functions and Structures of Environmentally Relevant Enzymes. The Kwansei Gakuin University Natural Science Review, 4. pp. 17-50.

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Abstract

The LH1 complex and a native form of the LH2 complex have been isolated from the carotenoidless mutants of R. sphaeroides and characterized. Transient Raman spectroscopy of the LHCs detected both the generation of the triplet state upon picosecond pulsed photoexcitation and the generation of the cation-radical state upon nanosecond pulsed photo excitation. EPR spectroscopy confirmed the generation of the cation radical, and showd that the unpaired electron is shared by two BChl a molecules. The yields of BChl a cation radical per pigment-protein complex in the LH1 and the LH2 complexes have been estimated to be about 80 and 50 % of that in the RC. The generation of the triplet state is ascribed to singlet homofission and the generation of the cation-radical state to charge separation both between the BChl pair covering the neighboring repeating subunits in the LHCs. Thus, these reactions, when an excess amount of photons is applied, originate from the unique assembly of the B850 BChl a molecules. The generation of the triplet state of BChl a, and subsequent transformation into the cation-radical state have been shown as intrinsic properties of the isolated, carotenoidless antenna complexes. In the carotenoid-containing LH2 complex, the cation-radical state of BChl a can not be generated because the triplet state of BChl a is quenched by carotenoid Thus, the photo-protective function of carotenoid against the photo-oxidation of BChl a is evidenced.

Item Type:	Artikel
Subjects:	Q Science > QD Chemistry
Divisions:	Fakultas Teknologi dan Desain > Teknik Sipil
Depositing User:	Admin Repository
Date Deposited:	15 Apr 2020 10:25
Last Modified:	03 Jun 2022 02:48
URI:	http://eprints.upj.ac.id/id/eprint/85

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