An isolated photosystem (PS) II reaction center (RC) with altered pigment content was obtained by chemical exchange of native chlorophyll a (Chl) with externally added Cu-Chl a (Cu-Chl). Pigment composition and spectroscopic properties of the RC exchanged with Cu-Chl were compared with native RC and RC treated with Chl in the same way. High-performance liquid chromatography analysis showed approximately 0.5 Cu-Chl per two pheophytin in the Cu-Chl-reconstituted RC preparation. Insertion of Cu-Chl resulted in a decrease in absorption at 670 nm and an increase at 660 nm, suggesting that the peripheral Chl may have been displaced. Fluorescence emission spectra of the Cu-Chl-reconstituted RC displayed a marked decrease in fluorescence yield and a blue shift of the band maximum, accompanied by the appearance of a broad peak at a shorter wavelength, indicating that energy transfer in the modified RC was disturbed by Cu-Chl, a quencher of the excited state. However, there were few differences in the circular dichroism (CD) spectra, suggesting that the arrangement of pigments and proteins responsible for the CD signal was not significantly affected. In addition, no obvious change in peptide components was found after the exchange procedure.

Strong light (800 mu mol photons/m(2) per s)-induced bleaching of the pigment in the isolated photosystem 11 reaction center (PSII RC) under aerobic conditions (in the absence of electron donors or acceptors) was studied using high-pressure liquid chromatography (HPLC), absorption spectra, 77K fluorescence spectra and resonance Raman spectra. Changes in pigment composition of the PSII RC as determined by HPLC after light treatment were as follows: with increasing illumination time chlorophyll (Chl) a and beta-carotene (beta-car) content decreased. However, decreases in pheophytin (Pheo) could not be observed because of the mixture of the Pheo formed by degraded chlorophyll possibly. On the basis of absorption spectra, it was determined that, with a short time of illumination, the initial bleaching occurred maximally at 680 nm but that with increasing illumination time there was a blue shift to 678 nm. It was suggested that P680 was destroyed initially, followed by the accessory chlorophyll. The activity of P680 was almost lost after 10 min light treatment. Moreover, the bleaching of Pheo and beta-car was observed at the beginning of illumination. After illumination, the fluorescence emission intensity changed and the fluorescence maximum blue shifted, showing that energy transfer was disturbed. Resonance Raman spectra of the PSII RC excited at 488.0 and 514.5 nm showed four main bands, peaking at 1527 cm(-1) (nu(1)), 1159 cm(-1) (nu(2)), 1006 cm(-1) (nu(3)), 966 cm(-1) (nu(4)) for 488.0 nm excitation and 1525 cm(-1) (nu(1)), 1159 cm(-1) (nu(2)), 1007 cm(-1) (nu(3)), 968 cm(-1) (nu(4)) for 514.5 nm excitation. It was confirmed that two spectroscopically different P-car molecules exist in the PSII RC. After light treatment for 20 min, band positions and bandwidths were unchanged. This indicates that carotenold configuration is not the parameter that regulates photoprotection in the PSII RC.

Effects of long term exposure to physical factors of space flight on dormant seeds were studied on plants derived from tomato seeds flown for 6 years on board of the space station MIR. Upon return to the Earth, the seeds were germinated and grown to maturity (first generation). A second generation of plants was grown from seeds collected from these plants. Samples from both generations of plants were compared to plants from parallel ground-based controls, and significant differences in growth and development were observed between these groups. The test plants exhibited higher variability in yield than control ones. Some of the test plants were infertile. Various differences in cell walls, chloroplasts and mitochondria were observed with an electron microscope. The results obtained point out to significant changes occurring on the molecular level in tomato plants. The leaves of the first generation plants were used for random amplified polymorphic DNA analysis. Among 40 random primers used in this experiment, 31 primers generated the same DNA bands type, and nine primers generated a different DNA band type. Two hundred and sixty-nine DNA bands were produced, among which 29 DNA bands were polymorphic with the percentage of polymorphism being 10.8%. Considering the specificity of the examined organelles, their sensitivity to environmental factors and dynamics, it can be assumed that these changes are an adaptive response of cells to alterations in their environment. These changes should be taken into consideration in developing and modifying life-support systems involving higher plants for long-functioning interplanetary stations.

在2001年2月8日英国出版的权威科学杂志NATURE上(Vol.409:739～743)，德国柏林马普学会生物物理化学研究所的Zouni A.,Witt H.T., Kern J.,Fromme P.,Krauβ N.,Saenger W.和Orth P.七位科学家发表了关于系统II的高分辨率晶体结构的重要论文，题目译为中文是“蓝藻Synechococcus elongatus光系统II的3.8埃分辨率的晶体结构”。首次报道了用X_射线衍射方法获得的具有放氧活性的光系统II反应中心的晶体结构数据，并且对蛋白亚基和色素的位置及定向进行了确定，还对一直困惑人们的放氧中心锰簇的位置、大小和性状进行了解析。这是人类首次获得光合作用光系统II的空间结构，是膜结构生物学的重大突破，是在原子水平上继1988年解析出紫色细菌光合作用反应中心空间结构之后探索生命奥秘的又一里程碑性质的工作。

It is well known that angiosperms need light to form chlorophyll. Photosystem biogenesis is not found in dark-grown angiosperm seedlings. Nelumbo nucifera, which has a unique position in the phylogeny of the angiosperm, is special in that its seeds contain chlorophyll and LHCII. In this report, it is showed that both PSII and PSI could be formed in lotus seedling during ten-day germination in dark. This can be proved by the following three evidences. First, with in situ fluorescence detection at 77K, lotus embryo had only single fluorescence emission peak at 678 nm before germination while this peak red shifted to 682 nm during the dark-grown process. At the same time, the peak at 691 nm belonging to PSII and the peak at 725nm emitted from PSI begin to appeared and increased gradually with prolong of the germination time. Second, with SDS-PAGE, PSI chlorophyll-protein complexes band could be showed clearly in lotus seedling grown in the dark for 10 days. Western Blots also demonstrated the existence of Lhca1 protein, which is part of the source of PSI fluorescence emission at 725nm; Third, measurement of electron transport activities showed that chloroplast isolated from dark-grown lotus seedling had PSI reduce activity, but no PSII oxygen evolving activity. After addition of electron donor DPC, the light-driven DCIP reduce activity could be detected. These results showed that even though the PSII and PSI formed in the dark-grown lotus seedling, the water-splitting system of PSII is underdeveloped.

Photosystem Ⅰ (PSⅠ) is a pigment_protein complex embedded in the photosynthetic membrane, which includes more than ten protein subunits, and catalyses the transfer of electrons from the PC to the Fd through a series of electron transfer components. There is considerable progress in the structural and functional study of PSⅠ in the past two decades, and especially in recent years. In this review, we describe the protein composition of PSⅠ and its characteristics, the three electron transfer processes that PSⅠ mediates, the unique light harvesting pigment_protein complex (LHCⅠ) of PSⅠ and the latest 4? resolution three_dimensional structural biology information of PSⅠ. We also foresee the future research of PSⅠ.

Inhibitor K-23 is a new highly efficient inhibitor of electron transfer in PSII of higher plants. Its inhibitory effect is based on the redox interaction with reaction center components of PSII and on the formation of a short cyclic electron transfer which leads to the reversible separation of photoinduced charge in PSII. However, its inhibitory site is not clear. In this report, we investigated the possible binding site of this inhibitor in PSII by the following aspects. 1) The effects of K-23 and DCMU on the oxygen evolution of trypsin-treated thylakoid were compared using ferricyanide as electron acceptor. It is suggested that even though inhibitory sites of K-23 and DCMU are at the acceptor side, their binding sites are different. 2) The effects of inhibitor K-23 on the content of plastoquinone in core complex of PSII were investigated by using HPLC method to identify the possible replacement of the primary electron acceptor of PSII, plastoquinone, at its binding site by the inhibitor K-23. It is found that inhibitor K-23 did not affect elution times of plastoquinone, but it affected the profiles of the absorption spectra. Inhibitor K-23 also results in the decrease of peak area of plastoquinone. 3) The absorption spectra showed that the absorption peak of plastoquinone at 262nm was disappeared in the presence of K-23. Analyzing the above results, we suggest that the K-23 binding at the QA site by reacting with it other than replacement of plastoquinone.

Photosystem Ⅰ (PSⅠ) is a pigment-protein complex embedded in the photosynthetic membrane, which includes more than ten protein subunits, and catalyses the transfer of electrons from the PC to the Fd through a series of electron transfer components. There is considerable progress in the structural and functional study of PSⅠ in the past two decades, and especially in recent years. In this review, we describe the protein composition of PSⅠ and its characteristics, the three electron transfer processes that PSⅠ mediates, the unique light harvesting pigment-protein complex (LHCⅠ) of PSⅠand the latest 4A resolution three-dimensional structural biology information of PSⅠ. We also foresee the future research of PSⅠ.

The spectroscopy characteristics and the fluorescence lifetime for the chloroplasts isolated from the pseudo ginseng, water hyacinth and spinach plant leaves have been studied by absorption spectra, low temperature steady-state fluorescence spectroscopy and single photon counting measurement under the same conditions and by the same methods. The similarity of the absorption spectra for the chloroplasts at room temperature suggests that different plants can efficiently absorb light of the same wavelength. The fluorescence decays in PS II measured at the natural Q A state for the chloroplasts have been fitted by a three-exponential kinetic model. The three fluorescence lifetimes are 30, 274 and 805 ps for the pseudo ginseng chloroplast; 138, 521 and 1494 ps for the water hyacinth chloroplast; 197, 465 and 1459 ps for the spinach chloroplast, respectively. The slow lifetime fluorescence component is assigned to a collection of associated light harvesting Chl a/b proteins, the fast lifetime component to the reaction center of PS II and the middle lifetime component to the delay fluorescence of recombination of P + 680 and Pheo - . The excitation energy conversion efficiency (η ) in PS II RC is defined and calculated on the basis of the 20 ps electron transfer time constant model, 60%, 87% and 91% for the pseudo ginseng, water hyacinth and spinach chloroplasts, respectively. This interesting result is in unconformity with what is assumed to be 100% efficiency in PS II RC. Our result in this work stands in line with the 20 ps electron transfer time constant in PS II rather sound and the water hyacinth plant grows slower than the spinach plant does as envisaged on the efficiency. But, our results predict that those plants can perform highly efficient transfer of photo-excitation energy from the light-harvesting pigment system to the reaction center (closely to 100%). The conclusion contained in this paper reveals the plant growth characteristics expressed in the primary processes of photosynthesis and a relationship between a plant growing rate and its spectroscopy characteristics and fluorescence lifetimes, namely, the slower a plant grows, the less excitation energy conversation efficiency used might be anticipated.

采用相同的分离技术, 从三七、水葫芦和菠菜植物叶子中提取叶绿体. 利用吸收光谱和低温荧光光谱及皮秒荧光单光子计数技术对这3种叶绿体的光谱性质和光系统Ⅱ荧光寿命进行了研究. 这3种叶绿体吸收光谱相似, 暗示着不同的植物都能高效吸收不同波长的光子. 采用三指数动力学模型对测定的光系统Ⅱ荧光衰减曲线拟合, 水葫芦植物叶绿体光系统Ⅱ荧光衰减寿命分别是: 138, 521和1494 ps; 菠菜体系叶绿体荧光寿命分别是: 197, 465和1459 ps; 三七叶绿体体系荧光寿命分别是: 30, 274和805 ps; 并且归属了荧光组分, 慢速度荧光衰减由叶绿素堆积造成, 中等速度荧光衰减源于PS Ⅱ反应中心重新结合电荷组分, 快速度荧光衰减归属于PS Ⅱ反应中心组分. 定义并且基于20 ps模型计算了三七、水葫芦和菠菜叶绿体光系统Ⅱ反应中心激发能转能效率, 分别是60%, 87%和91%. 实验结果支持20 ps时间常数模型. 三七叶绿体光系统Ⅱ反应中心低转能效率, 2个光系统之间激发能分配平衡状态差的结果, 以及它的光系统Ⅰ激发能红移的现象都与该植物生长速度慢的现象相吻合, 显示植物生长速度特性可体现在光合作用原初过程中, 表明植物生长速度与它的荧光性质及荧光寿命相关性, 生长慢的植物对吸收的光子能量利用效率较低, 而生长快的植物, 转能效率则较高.

We have studied the spectroscopic characteristics and the fluorescence lifetime for the PS II particles from pseudo ginseng, water hyacinth and spinach plant leaves by absorption spectra, low temperature steady- state fluorescence spectroscopy and single photon counting measurement under the same conditions. The absorption spectra for the PS II particles at room temperature are similar, which suggests that different plants can efficiently absorb light of the same wavelength. The fluorescence decays in PS II measured at the natural QA state for the PS II particles have been fitted by a three - exponential kinetic model. The three fluorescence lifetimes are 14 ps, 272 ps and 1840 ps for the pseudo ginseng PS II particles; 157 ps, 415 ps and 1661 ps for the water hyacinth PS II particles; 198 ps, 677 ps and 1244 ps for the spinach PS II particles, respectively. The slow lifetime fluorescence component is assigned to a collection of associated light harvesting Chi a/b proteins, the fast lifetime component to the reaction center of PS II and the middle lifetime component to the delay fluorescence of recombination of P-680(+) and Pheo(-). The excited energy conversion efficiency (eta) in PS II RC is 41%, 89%, 91% calculated on the 20 ps model for the pseudo ginseng, water hyacinth and spinach PS II particles, respectively. This interesting result is not consistent with what is assumed that the efficiency is 100% in PS II RC. Our result in this paper also presents a support for the 20 ps electron transfer time constant in PS II being more reasonable. However, our results show those plants can perform highly efficient transfer of photo - excitation energy from the light - harvesting pigment system to the reaction center (near 100%). The results in this paper further demonstrate that the characteristics with slow growth for pseudo ginseng plant is discernible in the primary processes of photosynthesis, plant growth is related with its spectroscopic characteristics and the fluorescence lifetime, and the slower a plant grows the less excited energy efficiency used should be anticipated.

The changes of chlorophyll-protein complexes and photosynthetic activities of chloroplast isolated from lotus (Nelumbo nucifera Gaertn.) seeds germinating under illumination were studied. SDS-PAGE analysis of chlorophyll-protein complexes showed that there was only the light harvesting chlorophyll a/b protein complex from PS II (LHC II) precursor in chloroplast from lotus seeds germinated for 2 to 6 days, while LHC-II1, and the chlorophyll-protein complex of PS I (CP I) appeared on the 8th day of germination and PS II reaction center complex appeared later. Studies on the polypeptides composition of the chloroplast revealed the following results: 1) Small amount of the 27 kD polypeptide was synthesized in invisible light; 2) The 30 kD polypeptide existed previously in the plumules of the dry seeds; 3) The amount of the 30 kD polypeptide was more than any other polypeptides before germination and decreased gradually throughout germination, while the 27 kD polypeptide changed in the opposite way; 4) In the process of germination, measurement of the electron transport rate and the fluorescence induction kinetics at room temperature showed that PS II activities and efficiency of primary light energy transformation were only experimentally measurable after 7 days of germination and gradually increased afterwards. At the same time, the chl a/b ratio rose from the lower value to normal; 5) The changes of chloroplast membrane components and its functions are concomitant in concert with that of the ultrastructure of chloroplast membranes during germination, as shown in our earlier work[6]. The results have proved again that a different developmental pathway of chloroplast is likely to exist in the lotus plumules, which might provide an important clue for N. nucifera in having an unique position in the phylogeny of the angiosperm.

光合作用中最核心的步骤之一是在反应中心进行的原初反应,PSⅡ反应中心原初反应的机理研究已日益成为国际光合作用研究的焦点这一.1987年Nanba和Satoh首次分离纯化出PSⅡ反应中心D1/D2/Cyt b559复合物以来,国际上对PSⅡ反应中心的原初电荷分离（Charge separation）、电荷重组（Charge recombination）和能量传递过程的动力学性质采用时间分辨荧光光谱和吸收光谱及烧孔谱（Hole-burning Spectroscopy）等技术进行研究,已取得一些有意义的结果.但是,由于PSⅡ反应中心中色素分子的吸收光谱重叠严重,其吸收光谱在675nm处仅有一个吸收峰,无法选择性地激发原初电子供体P680,实验得到的数据比较复杂,不同实验室得到的动力学数据以及对实验数据的解释,都存在较大差异,甚至完全相反.本文以菠菜叶绿体中的PSⅡ颗粒、PSⅡ核心复合物（CP47/CP43/D1/D2/Cyt b559）和PSⅡ反应中心复合物（D1/D2/Cyt b559）为材料,用皮秒和飞秒激光技术对光系统Ⅱ反应中心电荷分离和能量传递的动力学进行研究,测定出光系统Ⅱ反应中心内部β-胡萝卜素和原初电子供体P680之间的能量传递以及PSⅡ反应中心原初电荷分离的时间常数,提出了可能的动力学模型.