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Spectral Properties of Chlorophyll f in the B800 Cavity of Light-harvesting Complex 2 from the Purple Photosynthetic Bacterium Rhodoblastus acidophilus
Photochemistry and Photobiology ( IF 2.6 ) Pub Date : 2021-07-22 , DOI: 10.1111/php.13491
Yoshitaka Saga 1 , Aiko Tanaka 1 , Madoka Yamashita 1 , Toshiyuki Shinoda 2 , Tatsuya Tomo 2 , Yukihiro Kimura 3
Affiliation  

The interactions of chlorophyll (Chl) and bacteriochlorophyll (BChl) pigments with the polypeptides in photosynthetic light-harvesting proteins are responsible for controlling the absorption energy of (B)Chls in protein matrixes. The binding pocket of B800 BChl a in LH2 proteins, which are peripheral light-harvesting proteins in purple photosynthetic bacteria, is useful for studying such structure–property relationships. We report the reconstitution of Chl f, which has the formyl group at the 2-position, in the B800 cavity of LH2 from the purple bacterium Rhodoblastus acidophilus. The Qy absorption band of Chl f in the B800 cavity was shifted by 14 nm to longer wavelength compared to that of the corresponding five-coordinated monomer in acetone. This redshift was larger than that of Chl a and Chl b. Resonance Raman spectroscopy indicated hydrogen bonding between the 2-formyl group of Chl f and the LH2 polypeptide. These results suggest that this hydrogen bonding contributes to the Qy redshift of Chl f. Furthermore, the Qy redshift of Chl f in the B800 cavity was smaller than that of Chl d. This may have arisen from the different patterns of hydrogen bonding between Chl f and Chl d and/or from the steric hindrance of the 3-vinyl group in Chl f.

中文翻译:

紫色光合细菌嗜酸红芽孢杆菌捕光复合物 2 B800 腔中叶绿素 f 的光谱特性

叶绿素 (Chl) 和细菌叶绿素 (BChl) 色素与光合捕光蛋白中的多肽的相互作用负责控制蛋白质基质中 (B) Chls 的吸收能量。LH2 蛋白中 B800 BChl a的结合口袋是紫色光合细菌中的外周光捕获蛋白,可用于研究这种结构-性质关系。我们报告了来自紫色细菌嗜酸红芽孢杆菌的 LH2 的 B800 腔中 Chl f的重组,它在 2 位具有甲酰基。Chl f的 Q y吸收带与丙酮中相应的五配位单体相比,B800 腔中的波长移动了 14 nm 至更长的波长。这种红移大于 Chl a和 Chl b的红移。共振拉曼光谱表明Chl f的2-甲酰基与LH2多肽之间的氢键。这些结果表明这种氢键有助于Chl f的 Q y红移。此外, B800 腔中 Chl f的 Q y红移小于 Chl d的 Q y 红移。这可能是由于 Chl f和 Chl d之间的不同氢键模式引起的和/或来自 Chl f中 3-乙烯基的空间位阻。
更新日期:2021-07-22
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