Abstract
The LH2 antenna complexes containing neurosporene (the number of conjugated double bonds; (n = 9), spheroidene (n =10), spheoidenone (n = 11) and the carotenoids-less LH2 antenna complexes were prepared from the wild type and a mutant of Rba. sphaeroides. Also, the LH2 antenna complex containing rhodopinglycoside (n = 11) was prepared from Rps. acidophila (wild type). We irradiated them with red light (λ>760 nm), and examined the photo-protective function of carotenoids against the degradation of BChl a by probing the Qy absorption. We have obtained the following results: (1) Clear difference in the BChl degradation was found between the carotenoid-containing and the carotenoid-less LH2 antennas. (2) When n increased, the photo-protective function of carotenoid was enhanced. (3) B800 BChl was more sensitive to the photo-degradation than B850 BChl. When n increased, the difference between B800 and B850 increased.
