Development of Photosystem II in dark grown Chlamydomonas reinhardtii. A light-dependent conversion of PS IIβ, QB-nonreducing centers to the PS IIα, QB-reducing form

The green alga Chlamydomonas reinhardtii is a facultative heterotroph and, when cultured in the presence of acetate, will synthesize chlorophyll (Chl) and photosystem (PS) components in the dark. Analysis of the thylakoid membrane composition and function in dark grown C. reinhardtii revealed that photochemically competent PS II complexes were synthesized and assembled in the thylakoid membrane. These PS II centers were impaired in the electron-transport reaction from the primary-quinone electron acceptor, Q_A, to the secondary-quinone electron acceptor, Q_B (Q_B-nonreducing centers). Both complements of the PS II Chl a–b light harvesting antenna (LHC II-inner and LHC II-peripheral) were synthesized and assembled in the thylakoid membrane of dark grown C. reinhardtii cells. However, the LHC II-peripheral was energetically uncoupled from the PS II reaction center. Thus, PS II units in dark grown cells had a -type Chl antenna size with only 130 Chl (a and b) molecules (by definition, PS II units lack LHC II-peripheral). Illumination of dark grown C. reinhardtii caused pronounced changes in the organization and function of PS II. With a half-time of about 30 min, PS II centers were converted froma Q_B-nonreducing form in the dark, to a Q_B-reducing form in the light. Concomitant with this change, PS II units were energetically coupled with the LHC II-peripheral complement in the thylakoid membrane and were converted to a PS II form. The functional antenna of the latter contained more than 250 Chl(a+b) molecules. The results are discussed in terms of a light-dependent activation of the Q_A-Q_B electron-transfer reaction which is followed by association of the PS II unit with a LHC II-peripheral antenna and by inclusion of the mature form of PS II (PS II) in the membrane of the grana partition region.Abbreviations Chl chlorophyll - PS photosystem - Q_A primary quinone electron acceptor of PS II - Q_B secondary quinone electron acceptor of PS II - LHC light harvesting complex - F₀ non-variable fluorescence yield - F_plf intermediate fluorescence yield plateau leyel - F_max maximum fluorescence yield - F_i initial fluorescence yield increase from F₀ to F_pl (F_pl–F₀) - F_v total variable fluorescence yield (F_m–F0) - DCMU dichlorophenyl-dimethylurea     

Evolution of PS IIα and PS IIβ centers during the greening of Euglena gracilis Z: Correlations with changes in lipid content

The building up of the two types of reaction centers, PS II and PS II, was investigated during the greening of Euglena gracilis Z cells in resting medium. The maximal values in the proportion of PS II centers (55%) and in the oxygen evolved per chlorophyll were reached at the outbreak of greening, when accumulation of galactolipids (MGDG and DGDG) rich in unsaturated fatty acids occurred, and when anionic lipids (SQDG and PG) emerged. As the greening progressed, the chlorophyll accumulation corresponded to a secondary enrichment in PS II centers, which built up more rapidly than PS II centers; correlatively, a general saturation of the fatty acids constitutive of all lipid classes took place.Abbreviations DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - DGDG digalactosyldiacylglycerol - FAME Tatty acid methyl esters - HEPES acide (N-[2-hydroxyethyl]piperazine-N-[2-ethane sulfonic] - MGDG monogalactosyldiacylglycerol - PC phosphatidylcholine - PE phosphatidylethanolamine - PG phosphatidylglycerol - PQ plastoquinone - PS I Photosystem I - PS II Photosystem II - Q_A primary quinone electron acceptor of PS II - Q_B secondary quinone electron acceptor of PS II - SQDG sulfoquinovosyldiacylglycerol     

Functional characterization of the PS II–LHC II supercomplex isolated by a direct method from spinach thylakoid membranes

Recently, a novel procedure to isolate a highly pure and active Photosystem II preparation directly from thylakoid membranes, referred to as PS II–LHC II supercomplex, was reported [Eshaghi et al. (1999) FEBS Lett 446: 23–26]. In addition to the reaction center core proteins, the supercomplex contains all the extrinsic proteins of the oxygen evolving complex and a set of chlorophyll a/b binding proteins. In this paper, the functional properties of this isolated supercomplex are further characterized by using EPR spectroscopy, thermoluminescence, fluorescence relaxation kinetics and flash induced oxygen yield measurements. The PS II–LHC II supercomplex contains, in addition to Q_A and Q_B, a small pool of plastoquinone (PQ). Although the isolated complex is no longer membrane bound, it has preserved functional characteristics of a well defined PS II preparation with the exception of some modification of Q_B sites. This revised version was published online in June 2006 with corrections to the Cover Date.     

Iron components in PS II particles of spinach by Mössbauer spectroscopy

Mössbauer spectrum measured for the iron components of photosystem II (PS II) particles of spinach is a superposition of 4 doublets. Quadrupole splitting and chemical shifting of doublets I–IV are characteristics of proteins with oxidized cytochrome b-559, reduced cytochrome b-559, Fe³⁺-Q complex and Fe²⁺ -Q complex respectively. After the PS II particles are treated with La³⁺, two doublets of Fe²⁺ disappear and Fe²⁺ is converted into Fe³⁺, indicating that the reduced cytochrome b-559 has been converted into the oxidized cytochrome b-559, and Fe²⁺ -Q complex into Fe³⁺ -Q complex. The Mössbauer spectrum of PS II particles treated with La³⁺ and Ca²⁺ shows that Ca²⁺ can weaken the inhibitory effect of La³⁺ in part, and a portion of the reduced cytochrome b-559 and Fe-Q complex still exist.     

Fluorometric equipment for monitoring P680+• reduction in PS II preparations and green leaves

Newly developed equipment is described that permits the monitoring of laser flash induced transients of the normalised chlorophyll-a fluorescence quantum yield in isolated PS II preparations and whole leaves with a high time resolution. The essential operational unit of the set-up is a rapidly gated photomultiplier. In this way, the fluorescence artefact, due to the high intensity excitation laser flash, is sufficiently suppressed and the dead time of the signal response is reduced to about 500 ns. It is shown that the fluorescence rise kinetics in the s time-domain, after flash excitation is strongly dependent on the redox state of the primary electron donor of PS II (P680). At high excitation energies, the decay of carotenoid triplets, which are very efficient quenchers of chlorophyll singlet states, dominates the rise kinetics of the flash induced fluorescence yield in the s time domain.     

Functional analysis of the iron-stress induced CP 43′ polypeptide of PS II in the cyanobacterium Synechococcus sp. PCC 7942

Under conditions of iron-stress, the Photosystem II associated chlorophyll a protein complex designated CP 43, which is encoded by the isiA gene, becomes the major pigment-protein complex in Synechococcus sp. PCC 7942. The isiB gene, which is located immediately downstream of isiA, encodes the protein flavodoxin, which can functionally replace ferredoxin under conditions of iron stress. We have constructed two cyanobacterial insertion mutants which are lacking (i) the CP 43 apoprotein (designated isiA ^–) and (ii) flavodoxin (designated isiB ^–). The function of CP 43 was studied by comparing the cell characteristics, PS II functional absorption cross-sections and Chl a fluorescence parameters from the wild-type, isiA ^– and isiB ^– strains grown under iron-stressed conditions. In all strains grown under iron deprivation, the cell number doubling time was maintained despite marked changes in pigment composition and other cell characteristics. This indicates that iron-starved cells remained viable and that their altered phenotype suggests an adequate acclimation to low iron even in absence of CP 43 and/or flavodoxin. Under both iron conditions, no differences were detected between the three strains in the functional absorption crossection of PS II determined from single turnover flash saturation curves of Chl a fluorescence. This demonstrates that CP 43 is not part of the functional light-harvesting antenna for PS II. In the wild-type and the isiB ^– strain grown under iron-deficient conditions, CP 43 was present in the thylakoid membrane as an uncoupled Chl-protein complex. This was indicated by (1) an increase of the yield of prompt Chl a fluorescence (F_o) and (2) the persistence after PS II trap closure of a fast fluorescence decay component showing a maximum at 685 nm.Abbreviations Chl chlorophyll - CP 43, CP 47 and CP 43 Chl a binding protein complexes of indicated molecular mass - DCMU 3-(3,4-dichlorophenyl)-1,1-dimethylurea - F_m and F_m fluorescence when all PS II reaction centers are dosed in dark- and light-acclimated cells, respectively - F_o fluorescence when all PS II reaction centers are open in dark acclimated cells - F_v variable fluorescence after dark acclimation (F_m–F_o)     

亚硫酸对PSⅡ的伤害

从菠菜叶中提取PSII颗粒和叶绿体，经亚硫酸处理后发现，由PSII颗粒催化的DCIP光还原速率依SO3^2-学增高而降低，伤害部位发生于PSII的氧化侧，接近水的部位，在黑暗条件下H2O→DCIP和DPC→DCIP的电子传递均不受影响，在特定SO3^2-浓度下，PSII颗粒的伤害随处理时间的延长而加重，其伤害机理与33kD多肽的解离和Mn的流失有关，SO3^2-对新鲜叶绿体并不伤害，对老化的叶绿体则伤害明显，DCIP光还原速率依老化时间的延长而降低，Mn含量的减少与DCIP光还原速率的降低呈正相关，试样中添加FGTA后电子传递速率受害更为严重。     

PSⅠ的低温光抑制

简要介绍和阐述了PSⅠ的分子组成、电子传递体及其传递途径以及低温条件下PSⅠ光抑制的作用位点和可能的作用机制 ,并根据PSⅠ光抑制的特点 ,对其生理生化保护机制作了分析     

亚硫酸对PSⅡ的伤害

从菠菜叶中提取PSII颗粒和叶绿体,经亚硫酸处理后发现,由PSII颗粒催化的DCIP光还原速率依SO3^2-学增高而降低,伤害部位发生于PSII的氧化侧,接近水的部位,在黑暗条件下H2O→DCIP和DPC→DCIP的电子传递均不受影响,在特定SO3^2-浓度下,PSII颗粒的伤害随处理时间的延长而加重,其伤害机理与33kD多肽的解离和Mn的流失有关,SO3^2-对新鲜叶绿体并不伤害,对老化的叶绿体则伤害明显,DCIP光还原速率依老化时间的延长而降低,Mn含量的减少与DCIP光还原速率的降低呈正相关,试样中添加FGTA后电子传递速率受害更为严重。     

贵州灵芝科II

本文是作者贵州灵芝科研究的第二报。报道4个种,其中3个是新种。它们及其特征是：白边灵芝Ganoderma alblmarglnatum He,该种的菌盖红褐色至褐色,边缘白色,菌肉上层木材色,近菌管层淡褐色,菌管表面淡黄色,孢子较大(9.5一13.4×6.7—8.8μm)。它与闽南灵芝(G．Austrofujia-nense Zhao,Xu et Zhang)的区别为后者菌盖乌黑色或黑褐色,具污白色和褐色相间的环带,菌肉褐色,管面污白色,孢子较小(5．7—10．4×3.4—5.2μm)。它与黄边灵芝(G．Luteomarginatum Zhao,Xu et Zhang)的区别为后者菌盖黑褐色到暗褐色,边缘黄褐色,孢子较小(8.7一10.4×5.2—7μm)。兴义灵芝Ganoderma xingyiense He,该种的特征是菌盖近肾形,锈红色,似漆样光泽弱,有显著的辐射状纵皱,边缘稍钝,不整齐,波状;菌柄偏生到侧生,紫褐色,有强烈的似漆样光泽。尚未见有类似种类。拟层状灵芝 Ganoderma stroto-ideum He,该种的特征是子实体有柄,菌盖近漏斗状,表面乌红黑色,拟层状,具有光泽和无光泽相间的同心环带,菌肉厚达1cm,上层木材色,近菌管层淡褐色。它近于中国灵芝(G. sinense Zhao．Xu et Zhang),但后者菌盖非漏状,表面紫褐色并且非拟层状,菌肉均匀褐色,菌柄紫褐色。 以上所引证的标本保藏于贵州科学院生物研究所真菌标本室。     

云木香化学成分研究 II

从丽江产云木香（ＳａｕｓｓｒｅａｌａｐｐａＣ．Ｂ．Ｃｌａｒｋｅ）根中分离得到的另外７化合物,它们分别是孕甾炮醇酮（ｐｒｅｇｎｅｎｏｌｏｎｅ）（１）,β－谷甾醇（β－ｓｉｔｏｓｔｅｒｏｌ）（２）葫萝卜甙（ｄａｕｃｏｓｔｅｒｏｌ）（３）,苯丙素甙（ｓｙｒｉｎｇｉｎ）（４）,木质素甙（１－ｈｙｄｒｏｘｙｐｉｎｏｒｅｓｉｎｏｌ－１－β－Ｄ－ｇｌｕｃｏｐｙｒａｎｏｓｉｄｅ）（５）油酸（ｚ,ｚ）－９,１２－ｏ     

小麦叶片的状态转换涉及PSⅡ向PSⅠ激发能满溢的变化

叶片照远红光后,其叶绿素荧光参数Ｆｍ／Ｆｏ和两个光系统低温荧光产量Ｆ６８５／Ｆ７３５升高,照红光后,其Ｆｍ／Ｆｏ和Ｆ６８５＝Ｆ７３５降低;在照远荭光或红光过程中,与Ｆ６８５／Ｆ７３５的变化相比,Ｆｍ／Ｆｏ的变化幅度在较甜美的时间内最大;ＮａＦ预处理叶片经工光照射时,其Ｆｍ／Ｆｏ和Ｆ６８５／Ｆ７３５不增加ＤＣＭＵ预处理的叶片经红光照射时,这些结果表明,小麦叶片状态转换过程中两个光系统间能量分配贩变化     

小麦叶片的状态转换涉及PSⅡ向PSⅠ激发能满溢的变化

叶片照远红光后,其叶绿素荧先参数Fm／Fo和两个光系统低温荧光产量比值F685／F735升高,照红先后,其Fm／Fo和F685／F735降低;在照远红光或红先过程中,与F685／F735的变化相比,Fm／Fo的变化幅度在较短的时间内达到最大;NaF预处理的叶片经远红光照射时,其Fm／Fo和F685／F735不增加;DCMU预处理的叶片经红光照射时,其Fm／Fo和F685／F735降低的幅度比对照小。这些结果表明,小麦叶片状态转换过程中两个先系统间能量分配的变化至少部分地与激发能满溢变化有关。这种满溢的变化与捕光色素蛋白复合体LHCⅡ的磷酸化相联,并且,与光吸收截面变化相比,满溢的变化是对两个光系统不平衡光吸收的较快响应。     

PS1/GFP融合蛋白对PS1的亚细胞定位的初步研究

PS1基因突变与早发家族性老年痴呆有密切联系.构建pEGFP-C1-PS1以及pEGFP-N2-PS1融合基因表达载体,于HEK293和CHO细胞系中表达PS1/GFP融合蛋白,以GFP绿色荧光作为PS1的亚细胞定位信号,通过SPOTII以及CONFOCAL显微镜进行观察,初步获得PS1全长蛋白在细胞中定位的部分信息,即PS1定位于细胞核膜,细胞质内有不均匀的分布,少量存在于细胞-细胞接触处的细胞膜上.     

Free metal ion depletion by “good's” buffers: II. N-(2-acetamido)-2-aminoethanesulfonic acid (ACESH): Complexes with Calcium(II), Magnesium(II), Manganese(II), Cobalt(II), Zinc(II), Nickel(II), and Cooper(II)

Potentiometric, visible, and infrared studies of the complexation of N-(2-acetamido)-2-aminoethanesulfonic acid (ACESH) by Ca(II), Mg(II), Mn(II), Co(II), Zn(II), Ni(II), and Cu(II) are reported. Ca(II), Mg(II), and Mn(II) were found not to complex with ACES^?, while Co(II), Zn(II), Ni(II), and Cu(II) were found to form 2:1, ACES^? to M²⁺, complexes, and [Cu(ACES)₂] was found to undergo stepwise deprotonation of the amide groups to form [Cu(H_?1ACES)₂^2?]. Formation (affinity) constants for the various metal complexes are reported, and the probable structures of the various metal chelates in solution are discussed.     

Complexes of Co(II), Ni(II), Cu(II) and Zn(II) with 3′AMP and 2′AMP

Derivatives of Co(II), Ni(II), Cu(II) and Zn(II) with 3′AMP and 2′AMP were synthesized and characterized by IR UV-Vis and fluorescence spectroscopy. There seems to be bonding of the metal ion to the base in all cases. The activation test, using the complexes as allosteric labels, was carried out with rabbit muscle glycogen phosphorylase b, but the enzyme was not activated, confirming that the phosphate group must necessarily be bonded to position 5′ of the ribose in order to activate this enzyme.