Modeling of Optical Spectra of the Light-Harvesting CP29 Antenna Complex of Photosystem II鈥擯art II
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- 作者：Ximao Feng ; Adam Kell ; J枚rg Pieper ; Ryszard Jankowiak
- 刊名：The Journal of Physical Chemistry B
- 出版年：2013
- 出版时间：June 6, 2013
- 年：2013
- 卷：117
- 期：22
- 页码：6593-6602
- 全文大小：491K
- 年卷期：v.117,no.22(June 6, 2013)
- ISSN：1520-5207
文摘
Until recently, it was believed that the CP29 protein from higher plant photosystem II (PSII) contains 8 chlorophylls (Chl鈥檚) per complex (Ahn et al. Science2008, 320, 794鈥?97; Bassi et al. Proc. Natl. Acad. Sci. U.S.A.1999, 96, 10056鈥?0061) in contrast to the 13 Chl鈥檚 revealed by the recent X-ray structure (Pan et al. Nat. Struct. Mol. Biol. 2011, 18, 309鈥?15). This disagreement presents a constraint on the interpretation of the underlying electronic structure of this complex. To shed more light on the interpretation of various experimental optical spectra discussed in the accompanying paper (part I, DOI rg/10.1021/jp4004328">10.1021/jp4004328), we report here calculated low-temperature (5 K) absorption, fluorescence, hole-burned (HB), and 300 K circular dichroism (CD) spectra for CP29 complexes with a different number of pigments. We focus on excitonic structure and the nature of the low-energy state using modeling based on the X-ray structure of CP29 and Redfield theory. We show that the lowest energy state is mostly contributed to by a612, a611, and a615 Chl鈥檚. We suggest that in the previously studied CP29 complexes from spinach (Pieper et al. Photochem. Photobiol.2000, 71, 574鈥?89) two Chl鈥檚 could have been lost during the preparation/purification procedure, but it is unlikely that the spinach CP29 protein contains only eight Chl鈥檚, as suggested by the sequence homology-based study (Bassi et al. Proc. Natl. Acad. Sci. U.S.A.1999, 96, 10056鈥?0061). The likely Chl鈥檚 missing in wild-type (WT) CP29 complexes studied previously (Pieper et al. Photochem. Photobiol.2000, 71, 574鈥?89) include a615 and b607. This is why the nonresonant HB spectra shown in that reference were 1 nm blue-shifted with the low-energy state mostly localized on about one Chl a (i.e., a612) molecule. Pigment composition of CP29 is discussed in the context of light-harvesting and excitation energy transfer.