强光及外源活性氧对莴苣叶绿素荧光的影响

莴苣叶绿体在强光处理下发生光抑制,主要表现为叶绿素荧光参数Ｆｖ／Ｆｍ和ΦＰＳⅡ降低;外源活性氧Ｈ３Ｏ２,Ｏ＾－２,ＯＨ和＾１Ｏ２均能引起叶绿体ＰＳⅡ光化学效率Ｆｖ／Ｆｍ不同程度的下降,其中以＾１Ｏ２影响最明显：Ｈ２Ｏ２在诱导叶绿体荧光猝灭过程中,引起荧光产量降低,而使ｑｐ,ｑＮ,ΦＰＳⅡ,ＫＤ上升;     

高强光下SO^2—3和F^—对盐藻叶绿素荧光特性的影响

高强光下，盐藻以５０ｍｏｌ．Ｌ＾－１和ＳＯ６２－３和Ｆ＾－处理１ｈ后，其体内ＭＤＡ含量上升，ＳＯＤ活性，Ｆｖ／Ｆｍ，Ｆｖ／Ｆｏ，ＰＳⅡ电子传递活性和游离－ＳＨ含量均下降；２．以ＳＯ＾２－３处理后转置于低强江下３ｈ，ＤＮＡ含量下降，Ｆｖ／Ｆｍ，Ｆｖ／Ｆｏ，ΦＰＳⅡ和ＳＯＤ活性回升，游离－ＳＨ含量增加，暗下不能恢复；９３０以Ｆ＾－处理后无论在低强江或暗下上述指标都不能恢复，甚至继续发展。     

强光及活性氧对大豆光合作用的影响

利用叶绿素荧光技术研究了强光及活性氧对大豆（ Ｇｌｙｃｉｎｅ ｍａｘ Ｌ．） 光合作用的影响。结果表明,大豆叶片在强光（２０００ μｍｏｌ·ｍ － ２·ｓ－ １） 下照射２ ｈ 后,净光合放氧速率下降。随着处理光强的增加,叶绿素荧光参数Ｆｍ／Ｆｏ、Ｆｖ／ Ｆｍ 、ΦＰＳⅡ、ｑＰ 和ｑＮ 均呈下降趋势。在强光处理大豆叶片时,加入外源活性氧Ｈ２Ｏ２ 、Ｏ－·２ 、·ＯＨ 和１Ｏ２ 后,大豆叶片受到伤害。其中１Ｏ２ 和·ＯＨ 的破坏作用十分明显,表现为Ｆｖ／ Ｆｍ 和ΦＰＳⅡ的明显降低。抗氧化剂ＤＡＢＣＯ、甘露醇、抗坏血酸和组氨酸对强光下的大豆叶片有保护作用,但这种保护作用不强。在暗处理叶片时,超氧物歧化酶（ＳＯＤ）的抑制剂ＤＤＣ对Ｆｍ／ Ｆｏ 和Ｆｖ／Ｆｍ 的影响不大;抗坏血酸过氧化物酶（ＡＰＸ） 的抑制剂ＮａＮ３ 使Ｆｖ／Ｆｏ、Ｆｖ／ Ｆｍ和ΦＰＳⅡ下降明显。强光处理大豆叶片时,ＤＤＣ明显降低Ｆｍ／ Ｆｏ、Ｆｖ／ Ｆｍ 和ΦＰＳⅡ,ＮａＮ３ 降低Ｆｍ／ Ｆｏ、Ｆｖ／ Ｆｍ 和ΦＰＳⅡ的作用则更大。据此推测,在强光下大豆发生了光抑制,光抑制的发生与活性氧的存在有一定的关系     

蛋白质修饰剂,变性剂和活性氧对菠菜叶片光系统Ⅱ光失活的…

菠菜叶圆片以活性氧,蛋白质修饰剂和变生剂结合强光处理半小时,检测叶绿素荧光动力不并与单照强光的对照作比较,加入Ｈ２Ｏ２,Ｏ２＾－,ＯＨ和＾１Ｏ２等活性氧加剧了ＰＳⅡ的光抑制作用,Ｆｖ／Ｆｍ,ＱＰ和ΦＰＳⅡ降低,ｑＮ和１－ｑｐ相应上升,４种蛋白质修饰剂ＮＢＳ,ＤＥＰＣ,ＢＤＥ和ρＣＭＢ的处理,使叶片的Ｃｈｌ的荧光参数发生了与活性氧作用相类似的变化,尤以精氨酸残基悠剂ＢＤＥ的影响较为显著。     

光氧化胁迫下几种植物叶片的超氧自由基产生速率和光合特性

以甲基藉精（ＭＶ）Ｏ－１ｍｍｏｌ／Ｌ在１５００μｍｏｌ ｍ＾－２ａ＾－１光下处理Ｃ３植物花生、水稻和Ｃ４植物玉米、甘蔗的叶圆片３０ｍｍ,Ｏ２＾２＋产生速率随ＭＶ浓度提高而加快ＭＶ浓度超过１０μｍｏｌ／Ｌ,光合放氧出现负植并持续增大。光氧化作用降低叶绿素荧光参数ＦＶ／Ｆｍ,ΦＰＳⅡ和ｑｐ,而ｑＮ则或提高（Ｃ３植物,ＭＶ１０μｍｏｌ／Ｌ）或几平下）。热耗散系数ＫＤ的变化与ＱＮ相似。秘Ｃ４植物相比,Ｃ３     

玉米不同叶位叶片对光氧化的敏感性(简报)

玉米不同吐位叶片的ＳＯＤ和ＰＥＰＣａｓｅ活性和叶绿素含量呈单峰形,顶端下数第２位叶的活性最高。甲基紫精（ＭＶ）光氧化作用引起光合色素降解,Ｆｖ／Ｆｍ、ｑｐ和ΦⅲＰＳⅡ下降,ｑＮ和ＫＤ升高。第２位叶的变化较少,表现对光氧化较强的耐受力。未完全成熟的第１叶位地比成熟叶对光氧化的敏感性较高些。     

高温对生长在加富CO2条件下水稻离体叶片叶绿素荧光的影响

４个水稻品种ＩＲ７２、植朝２号、特三矮２号和Ⅱ优４４８０栽种于两种ＣＯ２浓度（３５０μＩＬ＾－１、６００μＩＬ＾－１）下,将其离体叶片不同温度（３０、３５、４０、４５、５０℃）处理３０ｍｉｎ后,其细胞膜渗漏率随处理温度的升高而上升,ＩＲ７２和桂朝２号在４０～４５℃之间有一个急剧上升的折点,而特三魏２号和Ⅱ优４４８０的折点则在４０～５０℃之间,Ｅｖ／Ｆｍ,Ｆｖ／Ｆｏ．ΦＰＳⅡ和ａＰ随处理温度的升高而     

光胁迫下杂种杨无性系光合生理生态特性的研究

以气体交换测定结合叶绿素荧光技术对几个杂种杨新无性系在自然光胁迫下的光合生理生态特性进行分析。８月ＣＯ２气体交换测定显示,中午存在明显的光合作用下降现象,同时某些无性系中午的气孔导度也有不同程度下降。叶绿素荧光分析显示,强光胁迫会影响光合作用的原初光化学反应过程,光系统Ⅱ（ＰＳＩＩ）反应中心的最大光化学量子产率,有效光化学量子产率等反映光系统Ⅱ反应中心活性的参数值在中午均比早晨低。与此同时,光系统Ⅱ反应中心的非光化学淬灭上升,他是光系统Ⅱ反应中心的一种自我保护机制。参数（Ｆｍ－Ｆｍｒ）／Ｆｍｒ、１—ｑｐ／ｑＮ和（Ｆ’ｍ－Ｆ）／Ｆ’ｍ可以反映各个无性系发生光抑制的可能性大小。由此计算出的各无性系发生光抑制的可能性排列次序与气体交换法测定的结果是一致的。     

青海高原及上海平原地区植物叶片光合作用的光抑制

用便携式ＡＤＣ光合气体分析系统和便携式ＣＦ－１０００荧光仪对青海和上海的同一植物和不同植物叶片光合作用的光抑制进行了测定。结果表明,两地在晴天强光下,中午植物叶片光系统Ⅱ（ＰＳⅡ）的光化学效率（Ｆｖ／Ｆｍ）和表观光合量子效率（ＡＱＹ）的日变化比早晨低;上海测定ＰＳⅡ的Ｆｖ／Ｆｍ和ＡＱＹ的日变化比青海的下降幅度大。ＡＱＹ的日变化曲线比ＰＳⅡ的Ｆｖ／Ｆｍ低,ＡＱＹ降低的幅度比ＰＳⅡ的Ｆｖ／Ｆｍ大。两地植物均有不同程度的光合作用光抑制,且上海比青海的大     

黄瓜幼苗子叶在低温下的光抑制及其恢复

用ＰＡＭ脉冲调制荧光仪测定叶绿素荧光的变化研究了黄瓜幼苗子叶在ＰＦＤ为５０和１００μｍｏｌｍ＾－２Ｓ＾－１,温度为４、７、１０、１５℃下 挑抑制及其恢复。结果表明,黄瓜幼苗子叶Ｆｖ／Ｆｍ随着温度的下降和ＰＦＤ的增加而下降,并且增加等量的ＰＦＤ在４℃下比在１０℃下引起更大的Ｆｖ／Ｆｍ下降。在黑暗条件下光抑制有轻微恢复,但完全发电和需光照,且恢复起始时的光照十分重要。     

HCO-3对植物生长发育及代谢的促进作用

重碳酸盐(bicarbonate, HCO^-₃)是碳酸盐岩经岩溶作用风化的产物,它深刻地影响着植物的生长发育和岩溶地区的生态环境。以往研究大都关注HCO^-₃对植物生长代谢的负面影响,如抑制植物的光合作用、降低碳氮代谢关键酶活性、破坏离子平衡等,少有人关注其对植物生长代谢的积极作用。该文依据前人的研究结果,综述了HCO^-₃对植物生长代谢的促进作用。已有的研究工作显示,HCO^-₃不仅在干旱等逆境胁迫下为植物提供短期的碳源和水源,促进气孔打开,恢复光合作用,而且通过调节碳氮代谢关键酶活性促进植物的碳氮代谢,参与调控植物的碳同化和氮还原等复杂的生理过程; 此外,HCO^-₃还通过影响葡萄糖代谢歧化,改变植物糖酵解途径和磷酸戊糖途径的分配,以增强植物的抗逆能力,从而获取生存机会。HCO^-₃的这些积极作用不仅使之成为促进植物生理代谢的关键因子,而且成为连接光合作用和岩溶作用的纽带。阐明HCO^-₃对植物生长发育的积极作用,可为维护喀斯特生态系统的生物多样性和稳定性、优化喀斯特生态系统功能提供理论依据。     

The photoproduction of H2 and NH+4 fixed from N2 by a derepressed mutant of Rhodospirillum rubrum

A mutant of Rhodospirillum rubrum has been isolated, after mutagenesis with nitrosoguanidine, which is characterized by its inability to grow in the light on malate-minimal media with exogenous ammonia or alanine, poor growth on glutamine and vigorous growth on glutamate. This mutant produces low levels of a key NH⁺₄ assimilation enzyme, glutamate synthase (NADPH-dependent). It also exhibits significant derepression of nitrogenase biosynthesis in the presence of ammonia or alanine, being 15% derepressed for the former and about 70% derepressed for the latter.Some of this mutant's fixed N₂ is excreted into the medium as NH⁺₄ (1 μmol NH⁺₄ per mg cell protein in 50 h). Nitrogenase-mediated H₂ production by this strain is considerable (42 μmol H₂ per mg cell protein in 50 h), approximately twice that of the wild type assayed under similar conditions.These results demonstrate that genetic alteration of the photosynthetic N₂-fixer's NH⁺₄ assimilation system disrupts the tight coupling of N₂ fixation and NH⁺₄ assimilation normally observed in these organisms, enabling photochemical conversion steps to be utilized for the photoproduction of NH⁺₄ and H₂.     

Solution-mediated syntheses and characterizations of two new zincophosphites [C6H14N2]0.5[Zn(H2PO3)2] and [C4H12N2]0.5[(CH3)2NH2][Zn2(HPO3)3]

Two new zincophosphites [C₆H₁₄N₂]_0.5[Zn(H₂PO₃)₂] 1 and [C₄H₁₂N₂]_0.5[(CH₃)₂NH₂][Zn₂(HPO₃)₃] 2 have been solvothermally synthesized in mixed solvents of N,N-dimethylformamide (DMF) and 1,4-dioxane (DOA), respectively. Single-crystal X-ray diffraction analysis reveals that compound 1 exhibits a neutral inorganic chain formed by ZnO₄ and HPO₂(OH) units. Interestingly, the left- and right-handed hydrogen-bonded helical chains are alternately formed via the hydrogen-bonds between two adjacent chains. Compound 2 exhibits a layer structure with 4- and 12-MRs formed by ZnO₄ and HPO₃ units, in which two kinds of organic amine molecules both act as countercations to compensate the overall negative electrostatic charge of the anionic network.     

Sn-S and Ru-Ru bonds cleavage reactions between [Ph3SnS(CH2)3SSnPh3] and Ru3(CO)12: X-ray crystal structures of [Ph3SnS(CH2)3SSnPh3] and trans-[Ru(CO)4(SnPh3)2]

The organotin complex [Ph₃SnS(CH₂)₃SSnPh₃] (1) was synthesized by PdCl₂ catalyzed reaction between Ph₃SnCl and disodium-1,3-propanedithiolate which in turn was prepared from 1,2-propanedithiol and sodium in refluxing THF. Reaction of 1 with Ru₃(CO)₁₂ in refluxing THF affords the mononuclear complex trans-[Ru(CO)₄(SnPh₃)₂] (2) and the dinuclear complex [Ru₂(CO)₆(μ-κ²-SCH₂CH₂CH₂S)] (3) in 20 and 11% yields, respectively, formed by cleavage of Sn-S bond of the ligand and Ru-Ru bonds of the cluster. Treatment of pymSSnPPh₃ (pymS = pyrimidine-2-thiolate) with Ru₃(CO)₁₂ at 55-60 °C also gives 2 in 38% yield. Both 1 and 2 have been characterized by a combination of spectroscopic data and single crystal X-ray diffraction analysis.     

Syntheses and characterization of the W(II) and W(III) N2 complexes, [WCl2(PMe3)3]2N2 and [WCl3(PMe3)2]2N2

Refluxing WCl₄(PMe₃)₃ under a nitrogen atmosphere in the presence of two equivalents of sodium amalgam leads to a reduction to the W(II) complex [cis,mer-WCl₂(PMe₃)₃]₂N₂ (1), which can be converted to [mer,trans-WCl₃(PMe₃)₂]₂N₂ (2) via appropriate oxidation/chlorination. Structural data have been obtained for both complexes, and demonstrate significantly increased steric crowding in 1 due to PMe₃/PMe₃ interactions. The N-N bond distances in the two compounds are similar, at 1.279(4) and 1.243(18) Å, respectively.     

Oxoselenide triangular molybdenum clusters: Synthesis and characterization of [Mo3SeO3(acac)3(py)3]PF6

New cluster complex [Mo₃SeO₃(acac)₃(py)₃]⁺ was obtained by ligand substitution in the aqua complex [Mo₃SeO₃(H₂O)₉]⁴⁺. Crystal structure was determined for [Mo₃SeO₃(acac)₃(py)₃]PF₆·C₆H₅CH₃. The complex was characterized by ⁷⁷Se NMR, electrospray mass-spectrometry, and cyclic voltammetry. DFT calculations were used to confirm the assignment of chemical shift and to study Mo-Mo bonding in the cluster core.     

Quadruplexes of human telomere dG3(TTAG3)3 sequences containing guanine abasic sites

This study was performed to evaluate how the loss of a guanine base affects the structure and stability of the three-tetrad G-quadruplex of 5′-dG₃(TTAG₃)₃, the basic quadruplex-forming unit of the human telomere DNA. None of the 12 possible abasic sites hindered the formation of quadruplexes, but all reduced the thermodynamic stability of the parent quadruplex in both NaCl and KCl. The base loss did not change the Na⁺-stabilized intramolecular antiparallel architecture, based on CD spectra, but held up the conformational change induced in dG₃(TTAG₃)₃ in physiological concentration of KCl. The reduced stability and the inhibited conformational transitions observed here in vitro for the first time may predict that unrepaired abasic sites in G-quadruplexes could lead to changes in the chromosome’s terminal protection in vivo.     

Synthesis and characterization of SrCu2(O2CR)3(bdmap)3 and Bi2(O2CCH3)4(bdmap)2(H2O) (R = CH3, CF3; bdmap = 1,3-bis(dimethylamino)-2-propanolato)

New mixed metal complexes SrCu₂(O₂CR)₃(bdmap)₃ (R = CF₃ (1a), CH₃ (1b)) and a new dinuclear bismuth complex Bi₂(O₂CCH₃)₄(bdmap)₂(H₂O) (2) have been synthesized. Their crystal structures have been determined by single-crystal X-ray diffraction analyses. Thermal decomposition behaviors of these complexes have been examined by TGA and X-ray powder diffraction analyses. While compound 1a decomposes to SrF₂ and CuO at about 380°C, compound 1b decomposes to the corresponding oxides above 800°C. Compound 2 decomposes cleanly to Bi₂O₃ at 330°C. The magnetism of 1a was examined by the measurement of susceptibility from 5–300 K. Theoretical fitting for the susceptibility data revealed that 1a is an antiferromagnetically coupled system with g = 2.012(7), −2J = 34.0(8) cm⁻¹. Crystal data for 1a: C₂₇H₅₁N₆O₉F₉Cu₂Sr/THF, monoclinic space group P2₁/m, A = 10.708(6), B = 15.20(1), C = 15.404(7) Å, β = 107.94(4)°, V = 2386(2) ų, Z = 2; for 1b: C₂₇H₆₀N₆O₉Cu₂Sr/THF, orthorhombic space group Pbcn, A = 19.164(9), B = 26.829(8), C = 17.240(9) Å, V = 8864(5) ų, Z = 8; for 2: C₂₂H₄₈O₁₁N₄Bi₂, monoclinic space group P2₁/c, A = 17.614(9), B = 10.741(3), C = 18.910(7) Å, β = 109.99(3)°, V = 3362(2) ų, Z = 4.     

Structure and thermal behavior of the layered zincophosphate [NH3-CH2-CH(NH3)-CH3](ZnPO4)2

A zinc phosphate with the composition [NH₃-CH₂-CH(NH₃)-CH₃](ZnPO₄)₂, containing the doubly protonated 1,2-diaminopropane (abbr. HDAP), was synthesized by hydrothermal crystallization of zinc nitrate, phosphoric acid, 1,2-diaminopropane and trimethylenedipiperidine. The single crystal analysis shows a layered inorganic-organic structure built up of a sandwich-like motif of alternating inorganic layers and HDAP cations (trimethylenedipiperidine not being a constituent of the structure). The HDAP species are found to be disordered and serve as bridges between two adjacent inorganic layers which are separated by 3.95 Å. The bridging interaction occurs via a hydrogen-bonding network. The inorganic layer features a pattern of four-membered rings involving two ZnO₄ and two PO₄ tetrahedra connected by sharing O atoms. Thermal analysis shows that the compound is stable up to 370 °C and that the thermal decomposition of HDAP occurs in two steps between 370 and 460 °C, causing the collapse of the structure. The first decomposition step corresponds to ammonia removal which proceeds with a high activation energy (E_a = 282 kJ mol⁻¹). The high E_a value is mainly attributed to strong electrostatic interactions between organic cations and anionic inorganic layers, the disruption of the interactions being the main reason for structural collapse after the HDAP removal.