发色团
紫色细菌
细菌叶绿素
光化学
化学
单重态
光合反应中心
化学物理
采光综合体
颜料
激发态
光合作用
电子转移
光系统II
原子物理学
物理
有机化学
生物化学
作者
A. A. Freer,Stephen M. Prince,Ken D. Sauer,Miroslav Z. Papiz,Anna Hawthornthwaite Lawless,Gerry McDermott,Richard J. Cogdell,Neil W. Isaacs
出处
期刊:Structure
[Elsevier]
日期:1996-04-01
卷期号:4 (4): 449-462
被引量:253
标识
DOI:10.1016/s0969-2126(96)00050-0
摘要
Background: Photosynthesis starts with the absorption of solar radiation by antenna pigment molecules. In purple bacteria these chromophores, (bacteriochlorophyll a and carotenoid) are embedded in the membrane; they are non-covalently bound to apoproteins which have the ability to modulate the chromophores' absorbing characteristics. The first structure of the bacterial antenna complex from Rhodopseudomonas acidophila, strain 10050, shows a ring of nonameric symmetry. Two concentric cylinders of apoproteins enclose the pigment molecules. The current resolution of the structure, to 2.5 å, allows us to begin to explore the mechanism of energy transfer among these pigments.Results The mechanism of energy transfer, from the short- to long-wavelength-absorbing pigments, is largely determined by the relative distances and orientations of the chromophores. In this paper we provide evidence that energy transfer between the B800 and B850 bacteriochlorophylls is largely via Förster induced dipole–dipole resonance. Strong Coulombic (exciton) coupling among the 18 short distanced chromophores in the B850 macrocycle is promoted by good alignment of the Qy dipoles. Singlet–singlet energy transfer from carotenoid to the B800 macrocycle appears to be minimal, with most of the energy transfer going to B850. The higher energy state of both chromophores dominates in more complex situations.Conclusion The structure of the antenna complex not only shows Nature at its most aesthetic but also illustrates how clever and efficient the energy transfer mechanism has become, with singlet–singlet excitation being passed smoothly down the spectral gradient to the reaction centre.
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