Characterization of the light-harvesting antennas of photosynthetic purple bacteria by stark spectroscopy .2. LH2 complexes: Influence of the protein environment
Characterization of the light-harvesting antennas of photosynthetic purple bacteria by stark spectroscopy .2. LH2 complexes: Influence of the protein environment
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DOI：
10.1021/jp963447w
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发表时间：
1997-09-11
影响因子：
3.3
通讯作者：
vanGrondelle, R
中科院分区：
文献类型：
--
作者：
Beekman, LMP;Frese, RN;vanGrondelle, R
我们对来自四种光合细菌的多种不同LH2配合物进行了低温Stark光谱分析，目的是表征B800和B850吸收特性的电场响应作为蛋白质环境的函数。研究了嗜酸红假单胞菌（Rps）的B800-850和B800-820 LH2配合物；球形红杆菌的B800-850、B800-840 （α - Tyr（+13）—>Phe）和B800-826 (α - Tyr（+13）—>Phe、α - Tyr（+14）—>Leu)；Ectothiorhodospira sp. B800-850和B800-830（在高LDAO下获得）；molischianum红螺旋菌b800 ~ 850；在所有这些情况下，B850的光谱蓝移归因于与细菌叶绿素a的乙酰羰基之间氢键相互作用的损失。850 nm波段和蓝移波段的\ δ mu\值都在3-4.5 D/f左右。氢键相互作用的损失对这些配合物中的\ δ mu\只有很小的影响。差极化率Tr（δ α）的值很大(600-1400埃（3)/f(2)）。根据基于晶体结构的LH2模型对结果进行了讨论，其中考虑了色素与色素和色素与蛋白质的相互作用；发现强烈的色素-色素相互作用尤为重要。在800 nm波段，δ mu\值很小，Rb的LH2配合物为1.0 ~ 1.5 D/f。球体和Rps。acidophila。然而，在Rsp。molischianum和Ectothiorhodospira sp. \Delta mu\值要大得多，约为3 D/f。B800波段的差异归因于Rsp中B800色素取向的差异。与Rps相比，molischianum和Ectothiorhodospira sp.。嗜酸菌和Rb。sphaeroides。由于取向的不同，Bchl a与周围蛋白质和邻近类胡萝卜素的相互作用也不相同。
We have performed low-temperature Stark spectroscopy on a variety of different LH2 complexes from four photosynthetic bacteria, with the aim of characterizing the electric field response of the B800 and B850 absorption properties as a function of the protein environment. The following LH2 complexes were investigated: B800-850 and B800-820 of Rhodopseudomonas (Rps) acidophila; B800-850, B800-840 (alpha Tyr(+13)-->Phe), and B800-826 (alpha Tyr(+13)-->Phe, alpha Tyr(+14)-->Leu) of Rhodobacter (Rb.) sphaeroides; B800-850 and B800-830 (obtained at high LDAO) of Ectothiorhodospira sp.; and B800-850 of Rhodospirillum (Rsp.) molischianum. For all these cases the spectral blue shift of B850 has been assigned to the loss hydrogen-bonding interaction with the acetyl carbonyl of bacteriochlorophyll a. \Delta mu\ values for the 850 nm bands as well as for the blue-shifted bands are all on the order of 3-4.5 D/f. The loss of hydrogen-bonding interactions has only small effects on \Delta mu\ in these complexes. The values of the difference polarizability, Tr(Delta alpha), are large (600-1400 Angstrom(3)/f(2)). The results are discussed in terms of crystal-structure-based models for LH2, in which pigment-pigment and pigment-protein interactions are considered; strong pigment-pigment interactions were found to be especially important. The values of \Delta mu\ for the 800 nm band are small, 1.0-1.5 D/f for LH2 complexes from Rb. sphaeroides and Rps. acidophila. However, in Rsp. molischianum and Ectothiorhodospira sp. \Delta mu\ values are much larger, of the order of 3 D/f. The difference in the B800 band is assigned to the difference in orientation of the B800 pigments in Rsp. molischianum and Ectothiorhodospira sp., as compared to the Rps. acidophila and Rb. sphaeroides. Due to the difference in orientation, the interactions of the Bchl a with the surrounding protein and neighboring carotenoid pigments are also not identical.