Energy Transfer and Photo-induced Electron Transfer in Photofunctional Molecule-Copolypeptide Complexes

叶绿素a （Ch1）和/或β -胡萝卜素(β -car) /共肽/表面活性剂体系的光谱研究已经进行，以模拟光合作用的早期事件。该共肽由带电氨基酸残基（L-Glu， L-Lys或L-Orn）和不带电的芳香氨基酸残基（L-Tyr， L-Trp或L-Phe）在pH约6.5下组成。以十六烷基三甲基氯化铵（CTAC）为阳离子表面活性剂，十二烷基硫酸钠（SDS）为阴离子表面活性剂。得到了以下显著的结果：表面活性剂离子协同结合在共肽链上形成胶束状团簇。Ch1和/或β -car被纳入这样的簇中，形成具有有序结构（α -螺旋或β -结构）的Ch1和/或β -car共肽复合物。在配合物中，从芳香氨基酸残基或β - car到Ch1的能量转移效率是表面活性剂浓度的函数。我们还根据福斯特理论确定了能量转移参数，如有效Ch1浓度和有效供体-受体平均距离。激光光解Ch1共肽复合物的研究表明，光诱导电子从芳香氨基酸残基转移到Ch1。讨论了电子传递途径的机理。配合物中Ch1的共振拉曼光谱强烈表明Ch1与L-Tyr和L-Trp相互作用，最可能是通过氢键，而不是通过L-Phe相互作用。

Spectroscopic studies of chlorophyll a (Ch1) and/or beta-carotene (beta-Car) /copolypeptide/surfactant systems have been carried out to model the early events in photosynthesis. The copolypeptides were composed of charged amino acid residues (L-Glu, L-Lys or L-Orn) and uncharged aromatic amino acid residues (L-Tyr, L-Trp or L-Phe) at around pH 6.5. We used cetyltrimethylammonium chloride (CTAC) as a cationic surfactant or sodium dodecyl sulfate (SDS) as anionic Surfactant. The following remarkable results were obtained.1. The surfactant ion bound cooperatively onto the copolypeptide chain to give a micelle-like cluster. Ch1 and/or beta-car were incorporated into such clusters to from Ch1 and/or beta-Car-copolypeptide complexes with the ordered structure (alpha-helix or beta-structure).2. The efficiencies of energy transfer from the aromatic amino acid residue or beta-Car to Ch1 in the complexes were determined as a function of surfactant concentration. We also determined energy-transfer parameters such as effective Ch1 concentrations and effective donor-acceptor mean distances on the basis of the Forster theoty.3. Laser flash photolysis studies of the Ch1 copolypeptide complexes revealed that photo-induced electron transfer took place from the aromatic amino acid residue to Ch1. The electron-transfer pathway mechanisms were discussed.4. Resonance Raman spectra of Ch1 in the complexes strongly suggested that Ch1 interacted with L-Tyr and L-Trp, most possibly through hydrogen bond, but not L-Phe.