COMPARISON OF CALCULATED AND EXPERIMENTALLY RESOLVED RATE CONSTANTS FOR EXCITATION-ENERGY TRANSFER IN C-PHYCOCYANIN .1. MONOMERS
COMPARISON OF CALCULATED AND EXPERIMENTALLY RESOLVED RATE CONSTANTS FOR EXCITATION-ENERGY TRANSFER IN C-PHYCOCYANIN .1. MONOMERS
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DOI：
10.1021/j100020a080
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发表时间：
1995-05-18
影响因子：
--
通讯作者：
BRYANT, DA
中科院分区：
文献类型：
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作者：
DEBRECZENY, MP;SAUER, K;BRYANT, DA
激发能量转移的光捕获蛋白质，C-藻蓝蛋白（PC），在单体聚集状态，分离自蓝藻聚球藻属PCC 7002的速率常数，计算使用福斯特理论和时间分辨荧光测量的结果进行比较。除了从PC的晶体结构获得的发色团之间的相对距离和取向之外，Forster计算还需要在PC单体中发现的发色团类型（β（155）、α（84）、β（84））的几种性质的光谱分辨率，包括吸收和荧光光谱、摩尔吸光系数、荧光量子产率和荧光寿命。前两个性质的分辨，发色团吸收和荧光光谱，在先前的论文中描述[Debreczeny等人，J. Phys. Chem. 1993，97，9852-9862]。PC单体中的能量转移速率常数的分配在此通过从野生型和突变株（cpcB/C155 S）分离的PC单体的时间分辨荧光各向异性测量来确认，所述突变株的PC缺失β（155）发色团。这些荧光各向异性测量还允许提取β（155）-β（84）（34度）和α（84）-β（84）（27度）发色团对内的发色团的跃迁偶极子之间的角度。在β（155）-β（84）α（84）-β（84）和β（155）-α（84）发色团对内能量转移的正向和反向计算的Forster速率常数之和的倒数值分别为49、158和890 ps，并且与实验测量值非常一致。它的结论是共振能量转移的弱耦合极限的福斯特模型成功地描述了占主导地位的能量转移过程中，这种蛋白质在单体状态。
Rate constants for excitation energy transfer in the light-harvesting protein, C-phycocyanin (PC), in the monomeric aggregation state, isolated from the cyanobacterium Synechococcus sp. PCC 7002, are calculated using Forster theory and compared with the results of time-resolved fluorescence measurements. In addition to the relative distances and orientations between chromophores, obtained from the crystal structure of PC, the Forster calculations require spectroscopic resolution of several properties of the chromophore types (beta(155), alpha(84), beta(84)) found in PC monomers, including absorption and fluorescence spectra, molar absorptivities, fluorescence quantum yields, and fluorescence lifetimes. The resolution of the first two properties, the chromophore absorption and fluorescence spectra, was described in a previous paper [Debreczeny et al. J. Phys. Chem. 1993, 97, 9852-9862]. The assignments of the energy-transfer rate constants in PC monomers are confirmed here by time-resolved fluorescence anisotropy measurements of the PC monomers isolated from both the wild-type and a mutant strain (cpcB/C155S) whose PC is missing the beta(155) chromophore. These fluorescence anisotropy measurements also allow one to extract the angles between the transition dipoles of the chromophores within the beta(155)-beta(84) (34 degrees) and alpha(84)-beta(84) (27 degrees) chromophore pairs. The values of the inverse of the sum of the forward and back calculated Forster rate constants for energy transfer within the beta(155)-beta(84) alpha(84)-beta(84), and beta(155)-alpha(84) chromophore pairs are 49, 158, and 890 ps, respectively, and are in excellent agreement with the experimentally measured values. It is concluded that the Forster model of resonant energy transfer in the weak coupling limit successfully describes the dominant energy-transfer processes in this protein in the monomeric state.