Femtosecond spectral and anisotropy study of excitation energy transfer between neighbouring α-80 and β-81 chromophores of allophycocyanin trimers
Femtosecond spectral and anisotropy study of excitation energy transfer between neighbouring α-80 and β-81 chromophores of allophycocyanin trimers
复制标题
别藻蓝蛋白三聚体相邻α-80和β-81发色团之间激发能量转移的飞秒光谱和各向异性研究
DOI：
10.1016/0005-2728(94)90055-8
复制
发表时间：
1994
期刊：
影响因子：
--
通讯作者：
T. Gillbro
中科院分区：
文献类型：
--
作者：
A. Sharkov;I. Kryukov;E. Khoroshilov;P. Kryukov;R. Fischer;H. Scheer;T. Gillbro
利用偏振泵浦-探测飞秒光谱技术研究了618 nm波长的230 fs脉冲激发后，别藻蓝蛋白（APC）三聚体在635-690 nm波长的光致光密度变化。在λ< 645 nm处观察到的初始漂白之后是亚皮秒吸收恢复，对应于在615 nm处用70-fs脉冲测量的430 ± 40 fs恢复动力学。只有APC吸收带的红色部分在激发后在3 ps处保持强烈漂白。光谱和动力学结果可以用APC三聚体的相邻α-80和β-81发色团之间的两种不同相互作用模型来描述。根据第一个，所观察到的亚皮秒动力学对应于激子耦合的、光谱相同的α-80和β-81发色团的水平之间的弛豫。在这种情况下，激发态吸收到双激发激子态应有助于测量的差谱。根据第二个，在APC三聚体中的飞秒激发能量转移发生在主要在620 nm处吸收的供体发色团和在650 nm处吸收的受体发色团之间。在第一个1.2 ps期间在615 nm处观察到的高各向异性值与施主-受主模型吻合得很好。在635-675 nm光谱区计算的各向异性值在3 ps激发后在0.1-0.25范围内，对应于施主和受主跃迁偶极取向之间的30°-45°角。在激发过程中在658 nm处获得的高各向异性可能是由于供体发色团的受激发射。
Polarization pump-probe femtosecond spectroscopy was used to investigate photoinduced optical density changes in allophycocyanin (APC) trimers at 635–690 nm after excitation with 230-fs pulses at 618 nm. The initial bleaching observed atλ< 645 nm is followed by subpicosecond absorption recovery corresponding to 430 ± 40 fs recovery kinetics measured at 615 nm with 70-fs pulses. Only the red part of the APC absorption band remains strongly bleached at 3 ps after excitation. The spectral and kinetic results can be described in terms of two different models of interaction between neighbouring α-80 and β-81 chromophores of APC trimers. According to the first one, the observed subpicosecond kinetics corresponds to relaxation between the levels of excitonically coupled, spectrally identical α-80 and β-81 chromophores. Excited state absorption to doubly excited excitonic state should in this case contribute to the measured difference spectra. According to the second one, the femtosecond excitation energy transfer in APC trimers takes place between a donor chromophore absorbing predominantly at 620 nm and an acceptor chromophore absorbing at 650 nm. The high anisotropy value observed at 615 nm during the first 1.2 ps is in good agreement with the donor-acceptor model. Anisotropy values calculated in the 635–675 nm spectral region at 3 ps after excitation are in the 0.1–0.25 range corresponding to an angle of 30°–45° between donor and acceptor transition dipole orientations. The high anisotropy obtained at 658 nm during the excitation is probably due to stimulated emission of the donor chromophore.