从捕光天线到反应中心分子能量传递研究

利用飞秒时间分辨光谱技术研究了PSⅡ中捕光天线LHCⅡ内Chla分子和β-Car分子传递光能到反应中心的时间特性,实验测得Chla分子用了25 ps,β-Car分子用了250 ps.理论研究得出:25 ps是相邻Chl分子之间随机转移传能的时间常数,250 ps是LHCⅡ内相邻β-Car分子,通过Chla分子单步FÖrster共振传递、Dexter电子交换机制、激子转移把能量转移到反应中心的总时间.理论计算与实验结果基本符合,激子随机转移传递激发能快而有效.     

Improving the stability of photosystem I–based bioelectrodes for solar energy conversion

Isolated photosystem I (PSI) has been integrated into numerous technologies for solar energy conversion. Interest in PSI is a consequence of its high internal quantum efficiency, thermal stability, ease of extraction, and adaptability. While there has been success in improving performance to elevate PSI biohybrid technologies toward a practical realm, the stability of PSI bioelectrodes is also of critical importance. Commercial solar energy conversion technologies are expected to achieve lifetimes of the order of ten years; however, many research-scale PSI bioelectrodes have only been tested for tens of days. Key areas affecting PSI bioelectrode stability include the effects of reactive oxygen species, immobilization strategies, and the environment within solid-state PSI biohybrid photovoltaics. At the current state, further investigation of long-term stability is necessary in enabling the development of PSI bioelectrodes for both photoelectrochemical cells and solid-state biohybrid photovoltaics.     

纳米氧化锌对细叶蜈蚣草(Egeria najas)光合作用的影响

采用细叶蜈蚣草(Egeria najas)作为受试植物,分别用不同浓度的ZnO NPs处理细叶蜈蚣草六天,通过OJIP荧光动力学曲线和脉冲瞬态荧光动力学曲线评估暴露在不同浓度的ZnO NPs悬浮液中的细叶蜈蚣草的光合性能。当细叶蜈蚣草暴露在ZnO NPs悬浮液中,光系统Ⅱ关闭的净速率（M_O）、J点的相对可变荧光强度（V_J）和单位反应中心用于热能耗散的能量（DI₀/RC）有明显的下降趋势（p<0.05）,最大光化学量子效率（Φ_P0）、捕获的激子中用来推动电子传递的效率（Ψ₀）、电子传递的量子产额（Φ_E0）、实际光化学量子效率（′_PSⅡ）有上升的趋势（p<0.05）。表明ZnO NPs增强了光系统Ⅱ反应中心之间的连通性、促进了光系统Ⅱ受体侧的电子传递和光能的利用,即ZnO NPs在某些方面促进了细叶蜈蚣草的光合作用。用相应浓度的Zn2+溶液来处理细叶蜈蚣草,当细叶蜈蚣草暴露在Zn2+溶液中,光系统Ⅱ关闭的净速率、J点的相对可变荧光强度和单位反应中心用于热能耗散的能量有明显的上升趋势（p<0.05）,最大光化学量子效率、捕获的激子中用来推动电子传递的效率、电子传递的量子产额、实际光化学量子效率有下降的趋势（p<0.05）,单位反应中心吸收的光能（ABS/RC）、捕获的光能（TR₀/RC）和非调节性能量耗散量子产量（′_NO）有明显的上升趋势（p<0.05）,即Zn2+降低了光系统Ⅱ反应中心之间的连通性、抑制了光系统Ⅱ受体侧的电子传递和光能的利用并使反应中心失活,即Zn2+抑制了细叶蜈蚣草的光合作用。在ZnO NPs处理细叶蜈蚣草的实验中并没有发现光合作用受抑制情况,表明ZnO NPs的促进作用强于其释放的游离Zn2+的抑制作用。     

Subcellular distribution of rare earth elements and characterization of their binding species in a newly discovered hyperaccumulator Pronephrium simplex

Subcellular distribution of rare earth elements (REEs, including 14 lanthanides and yttrium) in a newly discovered REE hyperaccumulator, Pronephrium simplex (P. simplex), was determined by a chemical sequence extraction followed by ICP-MS analysis. Results showed that most REEs are associated with cell wall and proteins, and REEs concentration in the proteins, 2899.5 μg g⁻¹, is much higher than those in the cell wall; in the chloroplast of P. simplex, REEs distribute almost equally in chloroplast membrane and thylakoid, while most REEs in the thylakoid are binding with photosystem II (PS II); a new REE-binding peptide in the lamina of P. simplex, which can accumulate REEs up to 3000 μg g⁻¹ and has higher affinity with light REEs, was characterized, indicating that its molecular mass is 5073 Da, and may have β-sheet structure; isoelectrofocusing electrophoretic photograph indicated that it is acidic peptide with IP of 3.7. Such information should be useful for understanding of both the storage and physiological role of REEs in P. simplex and further studies on the phytoremediation of REEs contaminated environments.     

Effect of the pH on the absorption spectrum of the isolated D1-D2-cytochrome b559 complex of photosystem II

The effect of pH on the Q_y absorption band has been studied in the isolated D1-D2-cytochrome b559 complex. The pH treatments are done on an ion-exchange chromatographic column. The absorption spectra at 77 K of the complex treated with acidic pH show irreversible loss of absorbance at both the blue and the red sides of the Q_y absorption band, with minima at 664.5 and 683.5 nm, respectively. These absorption changes are not accompanied by modifications in the Q_x absorption region characteristic of pheophytin pigments. Furthermore, the pigment composition of the D1-D2-cytochrome b559 complex remains unchanged after this treatment. The effects of basic pH are similar to those of acidic pH, but somewhat more pronounced. These results suggest that chlorophyll pigments absorbing at 664.5 and 683.5 nm are located on or close to the surface of the complex. Freezing/thawing cycle treatment first affects the band absorbing at 683.6 nm, indicating that it corresponds to the chlorophyll most exposed to the medium in the D1-D2-cytochrome b559 complex. At pH <5 a small reversible change at 672.5 nm is measured that correlates with a reversible change at 542 nm, indicating that inactive pheophytin a will absorb at this wavelength.     

Light- and heat-induced denaturation of photosystem II core-antenna complexes CP43 and CP47

Light- and heat-induced denaturation of the core-antenna complexes of Photosystem II, CP43 and CP47, purified from spinach, has been investigated using absorption, fluorescence and circular dichroism (CD) spectroscopy. Light is found to bring about considerable bleaching of chlorophyll a but no apparent change in the protein secondary structure, while heat induces significant unfolding of the protein secondary structure but no apparent destruction of the chlorophyll a molecule in the two antenna complexes. Both the destruction of chlorophyll a by light and the denaturation of the protein conformation by heat cause the loss of excitonic interaction of chlorophyll a in CP43 and CP47, as measured by visible CD activity. Light induces a larger decrease of the chlorophyll a fluorescence and the CD activity of CP47 than that of CP43, indicating that the native state of chlorophyll a of CP47 is more sensitive to light than that of CP43. The main thermal transitions of protein secondary structure occur at 50°C for CP43 and 63°C for CP47, while the half-loss of chlorophyll a excitonic interaction during heating occurs at 45°C for CP43 and 60°C for CP47, suggesting that CP47 is more thermally stable than CP43.     

生物合理设计光系统Ⅱ抑制剂研究(Ⅱ)——3-苯甲氨基-2-氰基-3-甲硫基丙烯酸乙酯的晶体及分子结构

合成了具有良好光合作用抑制活性的标题化合物,测定了其晶体结构,确定了该类化合物的顺反构型,阐明了苯环与氨基问亚甲基对化合物抑制活性的重要作用,解释了氨基氢与酯羰基氧问没有形成氢键的原因.     

生物合理设计光系统Ⅱ抑制剂研究(Ⅲ)——3-(4-氯苄胺基)-2-氰基-3-烷基丙烯酸酯类光合作用抑制剂的CoMFA研究

在除草剂的分子设计中,抑制光合作用除草剂的研究一直受到极大的关注．其中,氰基丙烯酸酯类化合物对光合作用中电子传递（即希尔反应）抑制活性较高［１,２］．研究表明,这类化合物在结构上的细微变化对希尔反应抑制活性的影响均很显著．因此,对这类抑制剂进行系统的...     

Photoinduced hydrogen evolution in an artificial system containing photosystemⅠ,hydrogenase,methyl viologen and mercaptoacetic acid

Hydrogen evolution was detected in an artificial system composed of light-harvesting unit of purified photosystem I,catalyst of hydrogenase,methyl viologen and electron donor under radiation.Absorption spectral features confirmed that electron transfer from electron donors to proton was via a photoinduced reductive process of methyl viologen.