Excitation energy distribution between two photosystems inPorphyra yezoensis and its significance in photosynthesis evolution

Comparative investigation on energy distribution between two photosystems were carried out in the sporo- phytes and gametophytes of Porphyra yezoensis. By perfor- ming 77 K fluorescence spectra, we suggested that there probably existed a pathway for energy transfer from PSⅡ to PSⅠ to redistribute the absorbed energy in gametophytes, while no such a way or at minor level in sporophytes. Electron transfer inhibitor DCMU blocked the energy transfer from PSⅡ to PSⅠ in gametophytes, but no obvious effects on sporophytes. These indicated that excitation energy distribution between two photosystems in gametophytes was more cooperative than that in sporophytes. These data in ontogenesis reflected the evolution process of photosynthetic organisms and supported the hypothesis of independent evolution of each photosystem.     

Kinetics of charge separation and energy transfer in photosystem II reaction center

Conclusion In the present study we investigated the kinetics of the initial charge separation and energy transfer in the PS II reaction center using pico-second and femto-second time-resolved techniques. We conclude that there are energy transfer processes between ?-Car or Pheo and P680 in the PSII reaction center. The time constant of energy transfer from Pheo to P680 is less than 100 ps, while that from (?-Car to P680 is about 350 ps. For the initial charge separation in the PS II reaction center, the preliminary finding supported the about 3-ps time constant of charge separation. The possible kinetic scheme in PS II reaction center was proposed. Further experiments are in progress.     

Changes in the transthylakoid proton gradient are caused by the movement of phycobilisomes in the cyanobacterium <Emphasis Type="Italic">Synechocystis</Emphasis> sp. strain PCC 6803

Phycobilisomes (PBSs) are the main accessory light-harvesting complexes in cyanobacteria and their movement between photosystems (PSs) affects cyclic and respiratory electron transport. However, it remains unclear whether the movement of PBSs between PSs also affects the transthylakoid proton gradient (ΔpH). We investigated the effect of PBS movement on ΔpH levels in a unicellular cyanobacterium Synechocystis sp. strain PCC 6803, using glycinebetaine to immobilize and couple PBSs to photosystem II (PSII) or photosystem I (PSI) by applying under far-red or green light, respectively. The immobilization of PBSs at PSII inhibited decreases in ΔpH, as reflected by the slow phase of millisecond-delayed light emission (ms-DLE) that occurs during the movement of PBSs from PSII to PSI. By contrast, the immobilization of PBSs at PSI inhibited the increase in ΔpH that occurs when PBSs move from PSI to PSII. Comparison of the changes in ΔpH and electron transport caused by the movement of PBSs between PSs indicated that the changes in ΔpH were most likely caused by respiratory electron transport. This will further improve our understanding of the physiological role of PBS movement in cyanobacteria.     

光照条件下Rose bengal处理对植物类囊体膜，PS II颗粒活性及多肽组分的影响

研究了Rose bengal处理对菠菜类囊体膜及PS II颗粒的叶绿素荧光发射光谱、蛋白质内源荧光发射光谱、DCIP光还原活性及多肽组分的影响。结果表明：单线态氧可改变类囊体膜的结构,并且可破坏PS II反应中心及LHC II中叶绿素分子的结合状态,引起类囊体膜PS II天线系统中的叶绿素捕光效率下降,还可引起光合电子传递能力下降和类囊体膜蛋白构象的改变,但至少在短时间内不会造成类囊体膜多肽组分的降解。     

2种水杨醛缩氨基酸及其10种金属配合物的杀菌活性研究

用浓度稀释法测定了2种席夫碱配体水杨醛缩甘氨酸、苯丙氨酸及其10种金属配合物对五种细菌(大肠杆菌、枯草杆菌、产气杆菌、金黄色葡萄球菌)的杀菌活性。结果表明，水杨醛缩甘氨酸仅对变形杆菌和金黄色葡萄球菌有杀菌活性，而水杨醛缩苯丙氨酸对上述五种菌种均无杀菌活性。铜、锌离子与上述配体结合形成配合物后，杀菌活性明显增强，对上述五种茸种均有较强的杀菌活性。而镍、钴、锰配合物的杀菌活性则较弱或没有杀菌作用。     

弱光和Tris处理条件下PSⅡ放氧核心复合物的损伤

弱光条件下(120μmol·m-2·s-1)用Tris(0.8mol/L,pH6.5～10.0)处理具有放氧活性的PSⅡ核心复合物,可引起33kD锰稳定蛋白的释放和锰复合物的破坏,并导致核心复合物的结构发生明显的改变.温和电泳、SDS-PAGE和双向电泳分析表明,主要是PSⅡ核心复合物的二聚体和单体减少,并且复合物部分解体;除反应中心D1和D2蛋白外,核心天线CP43和CP7的量也减少,33kD锰稳定蛋白要发生降解.避光时,PSⅡ核心复合物不受影响.     

水液相下赖氨酸钙(II)配合物旋光异构的DFT研究

该文采用DFT的M06-2X和MN15方法结合极化介质的SMD模型,研究了在水液相下两性赖氨酸分子2价钙配合物(Lys·Ca(II))的旋光异构.反应通道研究发现:Lys·Ca(II)的旋光异构可在Lys从两性异构为中性后,α-H以氨基N作桥和羰基O作桥迁移的2个通道上实现.势能面计算结果表明:,α-H以氨基N作桥的反应通道最具优势,在隐性水溶剂效应下决速步能垒为220.8 kJ·mol^-1,α-H从手性C向氨基N迁移的过渡态在显性水溶剂效应下的能垒降至120.5 kJ·mol^-1左右.研究结果表明:在水液相下手性Lys·Ca(II)的消旋过程十分缓慢,其用于生命体同补Lys和Ca(II)具有较好的安全性.     

Distribution of lanthanum among the chloroplast subcomponents of spinach and its biological effects on photosynthesis： location of the lanthanum binding sites in photosystem Ⅱ

The effects of lanthanum at different concentrations on the related photosynthetic activities of Hill reaction, Mg^2＋-ATPase and Ca^2＋-ATPase in spinach chloroplast were studied. Experimental results showed that lanthanum can increase all the activities at suitable concentration （15-30 mg· L^-1）, however, it behaves toxically on them when over used （60 mg. L^-1）. To get an improved understanding of the mechanism of lanthanum effects on the photosynthesis of spinach, the different subcomponents in the chloroplast of the cultured spinach were isolated, and the content of lanthanum in each subcomponent was determined by ICP-MS. The results obtained indicated that among these different subcomponents, about 90% out of the total chloroplast lanthanum was located in photosystem Ⅱ （PS Ⅱ） while there was little lanthanum in photosystem Ⅰ （PS Ⅰ）. Moreover, size exclusion high performance liquid chromatography （SE-HPLC） coupled with online UV and ICP-MS detections was novelly used for locating lanthanum binding sites in PS Ⅱ proteins for the first time. It was found that lanthanum has two binding sites in PS Ⅱ： La associates with chlorophyll together with magnesium in PS Ⅱ by partly replacing magnesium and also shares the common binding sites of PS Ⅱ proteins together with the inorganic cofactors of calcium and manganese, influencing the process of photosynthesis.     

New mechanism revealed for light-state transition in cyanobacterium Arthrospira platensis according to 77-K fluorescence kinetics

The mechanisms of oxygen evolution and carbon fixation in oxygenic organisms depend on the equal distribution of excitation energy to photosystems Ⅰ and Ⅱ, which is regulated by a mechanism referred to as light-state transition. In this work, a novel mechanism, energy spillover from PS Ⅰ to PS Ⅱ referred to as "inverse spillover", was revealed besides "mobile phycobilisome (PBS)" and the "spillover" of energy from PS Ⅱ to PS Ⅰ in cyanobacteria. Under continuous illumination with blue light, time-dependent 77-K fluorescence spectra demonstrated heterogeneous kinetics for the PBS and photosystem components, indicating that inverse spillover and mobile PBS work successively to regulate the excitation to a balanced distribution in cyanobacterial cells under blue light. Inverse spillover and mobile PBS occur under both 100 and 300 μmol m-2 s-1 blue-light conditions but they are accelerated under the latter.     

Crystal structure of plant photosystem I

Oxygenic photosynthesis is the principal producer of both oxygen and organic matter on Earth. The conversion of sunlight into chemical energy is driven by two multisubunit membrane protein complexes named photosystem I and II. We determined the crystal structure of the complete photosystem I (PSI) from a higher plant (Pisum sativum var. alaska) to 4.4 A resolution. Its intricate structure shows 12 core subunits, 4 different light-harvesting membrane proteins (LHCI) assembled in a half-moon shape on one side of the core, 45 transmembrane helices, 167 chlorophylls, 3 Fe-S clusters and 2 phylloquinones. About 20 chlorophylls are positioned in strategic locations in the cleft between LHCI and the core. This structure provides a framework for exploration not only of energy and electron transfer but also of the evolutionary forces that shaped the photosynthetic apparatus of terrestrial plants after the divergence of chloroplasts from marine cyanobacteria one billion years ago.     

不同产地南方红豆杉育种亲本叶绿素含量及荧光参数差异分析

【目的】准确选配南方红豆杉优良杂交育种亲本,高效地开展杂交育种试验。【方法】以30个不同产地南方红豆杉雌雄育种亲本为材料,测定了树高和胸径等生长性状以及叶绿素含量,并通过IMAGING-PAM荧光成像系统测定了PSⅡ叶绿素荧光参数,分析了亲本间生长性状、叶绿素含量和叶绿素荧光参数差异。【结果】南方红豆杉育种亲本树高、叶绿素含量和叶绿素荧光参数在产地间具有显著差异,而在性别间仅实际量子产量Y(Ⅱ)、调节性能量耗散的量子产量Y(NPQ)、q_P和F_v/F_m存在显著差异。从变异系数来看,亲本个体间表型性状变异超过15%。对比南方红豆杉雌雄株PSⅡ反应中心的光能利用效率发现,雌株的Y(Ⅱ)、q_P和F_v/F_m参数分别显著高出雄株的11.30%、4.28%和4.11%,雄株的Y(NPQ)较雌株则显著高出12.95%。光能分配模式方面,雌株吸收的光能41%用于光化学反应,而雄株仅37%。在欧氏距离为8处,表型聚类将南方红豆杉育种亲本划分为4个类群。其中第Ⅰ类表型性状表现一般,但PSⅡ光合效率优良; 第Ⅱ类表型性状和PSⅡ光合效率均最差; 第Ⅲ类表型性状和PSⅡ光合效率均较好; 第IV类表型性状和PSⅡ光合效率均最优。【结论】南方红豆杉雌株表型生长不如雄株,但PSⅡ反应中心光合效率高于雄株,可能与其具更大的生殖成本有关。南方红豆杉亲本类群中表型生长越优良,其PSⅡ指示光合效率的荧光参数越高,说明叶绿素荧光参数在一定程度上可以反映该亲本的生长状况,能为优良杂交育种亲本选配提供辅助参考。     

Three-dimensional structure of cyanobacterial photosystem I at 2.5 A resolution.

Life on Earth depends on photosynthesis, the conversion of light energy from the Sun to chemical energy. In plants, green algae and cyanobacteria, this process is driven by the cooperation of two large protein-cofactor complexes, photosystems I and II, which are located in the thylakoid photosynthetic membranes. The crystal structure of photosystem I from the thermophilic cyanobacterium Synechococcus elongatus described here provides a picture at atomic detail of 12 protein subunits and 127 cofactors comprising 96 chlorophylls, 2 phylloquinones, 3 Fe4S4 clusters, 22 carotenoids, 4 lipids, a putative Ca2+ ion and 201 water molecules. The structural information on the proteins and cofactors and their interactions provides a basis for understanding how the high efficiency of photosystem I in light capturing and electron transfer is achieved.     

ApcD is required for state transition but not involved in blue-light induced quenching in the cyanobacterium <Emphasis Type="Italic">Anabaena</Emphasis> sp. PCC7120

Pbycobilisomes （PBS） are able to transfer absorbed energy to photosystem Ⅰ and Ⅱ, and the distribution of light energy between two photosystems is regulated by state transitions. In this study we show that energy transfer from PBS to photosystem Ⅰ （PSI） requires ApcD. Cells were unable to perform state transitions in the absence of ApcD. The apcD mutant grows more slowly in light mainly absorbed by PBS, indicating that ApcD-dependent energy transfer to PSI is required for optimal growth under this condition. The apcD mutant showed normal blue-light induced quenching, suggesting that ApcD is not required for this process and state transitions are independent of blue-light induced quenching. Under nitrogen fixing condition, the growth rates of the wild type and the mutant were the same, indicating that energy transfer from PBS to PSI in heterocysts was not required for nitrogen fixation.     

3种药物及个人护理品对斜生栅藻生长及光系统Ⅱ的影响

研究了乳糖酸红霉素(ETM)、双氯芬酸钠(DCF)及壬基酚十氧乙烯醚(NPEO10)等3种药物及个人护理品(PPCPs)对斜生栅藻(Scenedesmus obliquus)的生长及光系统Ⅱ(PS Ⅱ)的影响。结果表明:3种PPCPs对斜生栅藻的生长及其PSⅡ均有抑制作用并以ETM的毒性最大,但NPEO10在低质量浓度时(0~0.05 mg/L)对斜生栅藻的生长及PSⅡ具一定的促进作用。对叶绿素荧光快速反应曲线的分析显示,ETM同时抑制斜生栅藻PSⅡ反应中心的供体侧和受体侧,使PSⅡ反应中心失活并降低光化学反应效率等,而DCF和NPEO10主要抑制电子传递链QA后的电子传递过程。研究显示叶绿素荧光诱导动力学参数对于反映PPCPs对藻类的毒性特征具有较高的敏感性及一定的特异性,可作为PPCPs污染生态风险评价的潜在候选生物标志物。     

二氯卡宾与苯环加成反应机理的量化研究

用限制的Hartree-Fock从头算分子轨道理论研究了单重态二氯卡宾与苯的环加成反应机理,采用HF/3-21G*方法计算了势能面上各驻点的构型参数、振动频率和能量.结果表明,该反应途径由两步组成:(I)两反应物(R1 R2)首先生成一复合物(CM),它是一无势垒的放热反应,放出的能量为5.70 kJ mol-1;(II)复合物(CM)经过渡态(TS)异构化为产物(P),其势垒为78.93 kJ mol-1.     

化学掺杂寡聚芴单元的(C∧N∧N)型环金属化铂配合物的合成及其光电性质

合成了一系列含寡聚芴单元的单核和双核(C~∧N~∧N)型(C~∧N~∧N=6-苯基-2,2′-二联吡啶)环金属化铂配合物,通过元素分析、核磁共振谱、高分辨质谱、紫外-可见光谱、荧光光谱和电化学等方法对配合物结构和光电性质进行了表征.研究结果表明,将具有高三线态能级的寡聚芴单元化学掺杂于[R(C~∧N~∧N)Pt](R=4-[对-(N-正丁基-N-苯基)苯胺基])配合物中,不改变配合物发光机制,各组分之间彼此能够保持相对独立的光谱和电化学性质.在以三聚芴为中间桥联基团而形成的线性双核配合物体系中,分子内存在由三聚芴单元向配合物单元的能量转移过程.     

2-巯基嘧啶互变异构的密度泛函理论计算

采用密度泛函理论,在B3LYP/6-3l1G**基组水平上,计算并考察了2-巯基嘧啶分子硫酮式和硫醇式结构进行结构互变的质子迁移过程中的2种可能途径:(a)分子内质子迁移,(b)水助质子迁移.计算结果表明,途经(b)所需的活化能较小,氢键在降低反应活化能方面起着重要作用.     

含钯(Ⅱ)-铁(Ⅲ)混合价金属有机化合物的研究──FcCH_2N(CH_3)_2-Pd-X-L类金属有机化合物的电化学性质和价电子互换作用

ＦｃＣＨ２Ｎ（ＣＨ３）２Ｐｄ－Ｘ－Ｌ是一类含有不同金属离子的混合价化合物．本文介绍合成方法并讨论不同性质的配位基以及配位基在分子中的键合情况对化合物Ｆｅ（Ⅱ）氧化电势的影响，剖析Ｆｅ（Ⅱ）－Ｐｄ（Ⅱ）价电子互换作用的条件和影响的因素．     

Evidence for wavelike energy transfer through quantum coherence in photosynthetic systems

Photosynthetic complexes are exquisitely tuned to capture solar light efficiently, and then transmit the excitation energy to reaction centres, where long term energy storage is initiated. The energy transfer mechanism is often described by semiclassical models that invoke 'hopping' of excited-state populations along discrete energy levels. Two-dimensional Fourier transform electronic spectroscopy has mapped these energy levels and their coupling in the Fenna-Matthews-Olson (FMO) bacteriochlorophyll complex, which is found in green sulphur bacteria and acts as an energy 'wire' connecting a large peripheral light-harvesting antenna, the chlorosome, to the reaction centre. The spectroscopic data clearly document the dependence of the dominant energy transport pathways on the spatial properties of the excited-state wavefunctions of the whole bacteriochlorophyll complex. But the intricate dynamics of quantum coherence, which has no classical analogue, was largely neglected in the analyses-even though electronic energy transfer involving oscillatory populations of donors and acceptors was first discussed more than 70 years ago, and electronic quantum beats arising from quantum coherence in photosynthetic complexes have been predicted and indirectly observed. Here we extend previous two-dimensional electronic spectroscopy investigations of the FMO bacteriochlorophyll complex, and obtain direct evidence for remarkably long-lived electronic quantum coherence playing an important part in energy transfer processes within this system. The quantum coherence manifests itself in characteristic, directly observable quantum beating signals among the excitons within the Chlorobium tepidum FMO complex at 77 K. This wavelike characteristic of the energy transfer within the photosynthetic complex can explain its extreme efficiency, in that it allows the complexes to sample vast areas of phase space to find the most efficient path.