Abstract:

Fluorescence spectra of native purple bacterial reaction center (RC) and bacterial pheophytin (Bphe) replaced RCs were obtained from 600 nm to 900 nm with a selective excitation at 597 nm. With the help of measuring the fluorescence from bacterial chlorophyll, bacterial pheophytin and plant pheophytin, the corresponding components in the RCs are classified for fluorescence emission. Results showed that pheophytin substitution influences the composition of fluorescence spectra. Therefore, four, three and two components were obtained from fluorescence spectra of native RC, Bphe B-replaced RC and Bphe A,B-replaced RC, respectively. Fluorescence components are well correlated to the binding of plant pheophytin. The decay of excited state of primary electron donor P in different RCs was also studied by measuring the fluorescence decay at 686.4, 674.1 and 681.1 nm, respectively. The decaying kinetics changed in different RCs, indicating that pheophytin replacement influenced the energy transduction and primary photochemical reaction in purple bacterial reaction centers.

去镁叶绿素置换细菌去镁叶绿素对紫细菌反应中心皮秒荧光的影响
邹永龙1 赵福利2 汪河洲2 夏安东2 曾小华1  徐春和1*

（1. 中国科学院上海生命科学研究院植物生理研究所，上海200032；
2. 中山大学超快速激光光谱学国家重点实验室，广州510270）

摘要：选择597 nm作为激发波长,探测范围为600～900 nm的荧光特性,分析了天然反应中心和两种去镁叶绿素置换的紫细菌反应中心的荧光发射光谱.借助细菌叶绿素、细菌去镁叶绿素和植物去镁叶绿素的荧光光谱,对相关组分进行了归类.实验结果表明选择性地置换细菌去镁叶绿素影响了荧光光谱的组成.在天然反应中心、BpheB置换的反应中心和BpheA,B置换的反应中心中可分别解析到4、3和2个荧光发射组分.研究肯定荧光发射组分与去镁叶绿素的结合存在对应关系.实验还分别在686.4、674.1和681.1 nm处测定了不同反应中心内的原初电子供体P的激发态通过荧光衰减的过程,观测到衰减动力学上的差异.说明去镁叶绿素置换影响了细菌反应中心内激发光能传递和原初光化学反应过程.

关键词： 去镁叶绿素置换；皮秒荧光；紫细菌；反应中心

Key words: pheophytin replacement, picosecond fluorescence, purple bacterial, reaction center