Mechanism of the carotenoid-to-bacteriochlorophyll energy transfer via the S1 state in the LH2 complexes from purple bacteria

被引:142
作者
Zhang, JP
Fujii, R
Qian, P
Inaba, T
Mizoguchi, T
Koyama, Y [1 ]
Onaka, K
Watanabe, Y
Nagae, H
机构
[1] Kwansei Gakuin Univ, Fac Sci, Dept Chem, Nishinomiya, Hyogo 6628501, Japan
[2] Kwansei Gakuin Univ, Fac Sci, Dept Phys, Nishinomiya, Hyogo 6628501, Japan
[3] Kobe City Univ Foreign Studies, Nishi Ku, Kobe, Hyogo 6512187, Japan
关键词
D O I
10.1021/jp993970l
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
This investigation was motivated by a desire to get a deeper insight into the mechanism of carotenoiod-to-bacteriochlorophyll (Car-to-BChl) energy transfer proceeding via the carotenoid S-1 state. (Here, we call the 2A(g)(-) and 1B(u)(+) states "the S-1 and S-2 states" according to the notation presently accepted.) To systematically examine the effect of the conjugation length of carotenoid on the rate and efficiency of the Car(S-1)-to-BChl(Q(y)) energy transfer, we performed the following experiments. (1) Subpicosecond time-resolved absorption spectroscopy was employed to measure the S-1-state lifetimes of lycopene (number of conjugated C=C bonds, n = 11), spheroidene (n = 10), and neurosporene (n = 9), both free in n-hexane and bound to the LH2 complexes from Rhodospirillum molischianum (Rs. molischianum), Rhodobactor sphaeroides (Rb. sphaeroides) 2.4.1, and Rb. sphaeroides G1C, respectively. The lifetime of each free (bound) carotenoid was determined to be 4.7(3.4) ps for lycopene, 9.3(1.7) ps for spheroidene, and 21.2(1.3) ps for neurosporene. It was found that the rate and the efficiency of the Car(S1)-to-BChl(Q(y),) energy transfer increase systematically when the number of conjugated C=C bonds decreases. (2) High-sensitivity steady-state fluorescence spectroscopy was used to measure the spectra of dual emission from the S-2 and S-1 states for the above carotenoids dissolved in n-hexane. The fluorescence data, combined with the above kinetic data, allowed us to evaluate the magnitudes of the transition-dipole moments associated with the Car(S-1) emission. It was found that the S-1 emissions of the above carotenoids carry noticeably large oscillator strengths (transition-dipole moments). In the case of the LH2 complex from Rs. molischianum, whose structural information is now available, the time constant of the Car(S1)-to-BChl(Q(y)) energy transfer (18.6 ps), which was predicted on the basis of a Car(S-1)-to-BChl(Q(y)) full Coulombic coupling scaled by the ratio of the S1 vs St transition dipole moments, was in good agreement with the one spectroscopically determined (12.3 ps). The oscillator strength associated with the Car(S1) emission was discussed in terms of the state mixing between the carotenoid S-2 and S-1 states.
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页码:3683 / 3691
页数:9
相关论文
共 52 条
[1]   ABSORPTION SPECTRAL SHIFTS OF CAROTENOIDS RELATED TO MEDIUM POLARIZABILITY [J].
ANDERSSON, PO ;
GILLBRO, T ;
FERGUSON, L ;
COGDELL, RJ .
PHOTOCHEMISTRY AND PHOTOBIOLOGY, 1991, 54 (03) :353-360
[2]   ENVIRONMENTAL EFFECTS ON RADIATIVE RATE CONSTANTS WITH APPLICATIONS TO LINEAR POLYENES [J].
ANDREWS, JR ;
HUDSON, BS .
JOURNAL OF CHEMICAL PHYSICS, 1978, 68 (10) :4587-4594
[3]   Characterization of the light-harvesting antennas of photosynthetic purple bacteria by stark spectroscopy .2. LH2 complexes: Influence of the protein environment [J].
Beekman, LMP ;
Frese, RN ;
Fowler, GJS ;
Picorel, R ;
Cogdell, RJ ;
vanStokkum, IHM ;
Hunter, CN ;
vanGrondelle, R .
JOURNAL OF PHYSICAL CHEMISTRY B, 1997, 101 (37) :7293-7301
[4]  
BOSE SK, 1963, BACTERIAL PHOTOSYNTH, P501
[5]  
Britton G., 1995, Carotenoids: Spectroscopy, V1B, P13
[6]  
Britton G, 1993, CAROTENOIDS PHOTOSYN, P252, DOI DOI 10.1007/978-94-011-2124-8_8
[7]  
CHANG JC, 1977, J CHEM PHYS, V67, P3901, DOI 10.1063/1.435427
[8]   ENERGY-TRANSFER BETWEEN THE CAROTENOID AND THE BACTERIOCHLOROPHYLL WITHIN THE B-800-850 LIGHT-HARVESTING PIGMENT-PROTEIN COMPLEX OF RHODOPSEUDOMONAS-SPHAEROIDES [J].
COGDELL, RJ ;
HIPKINS, MF ;
MACDONALD, W ;
TRUSCOTT, TG .
BIOCHIMICA ET BIOPHYSICA ACTA, 1981, 634 (01) :191-202
[9]   HOW CAROTENOIDS FUNCTION IN PHOTOSYNTHETIC BACTERIA [J].
COGDELL, RJ ;
FRANK, HA .
BIOCHIMICA ET BIOPHYSICA ACTA, 1987, 895 (02) :63-79
[10]   Energy transfer between carotenoids and bacteriochlorophylls in light-harvesting complex II of purple bacteria [J].
Damjanovic, A ;
Ritz, T ;
Schulten, K .
PHYSICAL REVIEW E, 1999, 59 (03) :3293-3311