Ultrafast carotenoid-to-chlorophyll singlet energy transfer in the cytochrome b6f complex from Bryopsis corticulans.
Ultrafast carotenoid-to-chlorophyll (Car-to-Chl) singlet excitation energy transfer in the cytochrome b(6)f (Cyt b(6)f) complex from Bryopsis corticulans is investigated by the use of femtosecond time-resolved absorption spectroscopy. For all-trans-alpha-carotene free in n-hexane, the lifetimes of the two low-lying singlet excited states, S(1)(2A(g)(-)) and S(2)(1B(u)(+)), are determined to be 14.3 +/- 0.4 ps and 230 +/- 10 fs, respectively. For the Cyt b(6)f complex, to which 9-cis-alpha-carotene is bound, the lifetime of the S(1)(2A(g)(-)) state remains unchanged, whereas that of the S(2)(1B(u)(+)) state is significantly reduced. In addition, a decay-to-rise correlation between the excited-state dynamics of alpha-carotene and Chl a is clearly observed. This spectroscopic evidence proves that the S(2)(1B(u)(+)) state is able to transfer electronic excitations to the Q(x) state of Chl a, whereas the S(1)(2A(g)(-)) state remains inactive. The time constant and the partial efficiency of the energy transfer are determined to be 240 +/- 40 fs and (49 +/- 4)%, respectively, which supports the overall efficiency of 24% determined with steady-state fluorescence spectroscopy. A scheme of the alpha-carotene-to-Chl a singlet energy transfer is proposed based on the excited-state dynamics of the pigments.
Zuo
Ping
P
State Key Laboratory for Structural Chemistry of Unstable and Stable Species, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
Li
Bin-Xing
BX
Zhao
Xiao-Hui
XH
Wu
Yi-Shi
YS
Ai
Xi-Cheng
XC
Zhang
Jian-Ping
JP
Li
Liang-Bi
LB
Kuang
Ting-Yun
TY
D002338:Carotenoids / Q000737:chemistry*; D002734:Chlorophyll / Q000737:chemistry*; D000460:Chlorophyta / Q000737:chemistry* / Q000502:physiology; D045346:Cytochrome b6f Complex / Q000737:chemistry*; D004735:Energy Transfer; D006586:Hexanes / Q000737:chemistry; D013050:Spectrometry, Fluorescence
D006586:Hexanes; D002734:Chlorophyll; D002338:Carotenoids; C041635:alpha-carotene; D045346:Cytochrome b6f Complex