Cyt b-559 链Arg18和Ser24的定点突变及其对PSII功能的影响

Cyt b-559是光系统II反应中心的成分之一，它由亚基和亚基组成的。在Cyt b-559中，血红素辅基与两个亚基中的组氨酸连接成有功能的蛋白，并维持PSII的功能稳定性。前人曾将与血红素相连的His突变，导致Cyt b-559功能和PSII稳定性的丧失。基于此研究，本文采用定点突变技术，将亚基中与His23位置最近的上游氨基酸Arg18分别用Gly和Glu取代，下游氨基酸Ser24用Phe取代，获得了衣藻Cyt b-559的突变体。对突变体的分析，有以下新结果：突变体都能进行光合自养，但无论在异养培养基上还是自养培养基上，和对照相比，其生长速度非常缓慢; PSII的活性分析，表明PSII的放氧活性为野生衣藻细胞的50%～80%， Fv/Fm 的荧光参数为40%～70%;对突变体进行强光（1000μE•m-2•s-1）照射，10min后，其放氧活性都降低为0，而野生型衣藻还保持35%的活性;提取类囊体膜蛋白，进行SDS-PAGE电泳和Western-blotting分析，显示突变体的膜蛋白与对照无显著差异。这些结果说明对围绕血红素环境的固有氨基酸的改变，虽然并没有明显影响类囊体膜蛋白的表达和组成，但是却影响了衣藻细胞的生长和PSII的活性，增加了衣藻细胞对强光的敏感性，降低了衣藻细胞自身的光保护能力。这说明靠近血红素配位环境的氨基酸Arg和Ser，尤其是Arg，对Cyt b-559的功能维持不可缺少，对于维持PSII的活性也很重要。

Phylogeny and biogeography of Chinese sisorid catfishes re-examined using mitochondrial cytochrome b and 16S rRNA gene sequences

The family Sisoridae is one of the largest and most diverse Asiatic catfish families, most species occurring in the water systems of the Qinhai-Tibetan Plateau and East Himalayas. To date published morphological and molecular phylogenetics hypotheses of sisorid catfishes are part congruent, and there are some areas of significant disagreement with respect to intergeneric relationships. We used mitochondrial cytochrome b and 16S rRNA gene sequences to clarify existing gaps in phylogenetics and to test conflicting vicariant and dispersal biogeographical hypotheses of Chinese sisorids using dispersal-vicariance analysis and weighted ancestral area analysis in combination with palaeogeographical data as well as molecular clock calibration. Our results suggest that: (1) Chinese sisorid catfishes form a monophyletic group with two distinct clades, one represented by (Gagata (Bagarius, Glyptothorax)) and the other by (glyptosternoids, Pseudecheneis); (2) the glyptosternoid is a monophyletic group and Glyptosternum, Glaridoglanis, and Exostoma are three basal species having a primitive position among it; (3) a hypothesis referring to Pseudecheneis as the sister group of the glyptosternoids, based on morphological evidence, is supported; (4) the genus Pareuchiloglanis, as presently defined, is not monophyletic; (5) congruent with previous hypotheses, the uplift of Qinghai-Tibetan Plateau played a primary role in the speciation and radiation of the Chinese sisorids; and (6) an evolutionary scenario combining aspects of both vicariance and dispersal theory is necessary to explain the distribution pattern of the glyptosternoids. In addition, using a cytochrome b substitution rate of 0.91% per million years and 0.23% for 16S rRNA, we tentatively date that the glyptosternoids most possibly originated in Oligocene-Miocene boundary (19-24Myr), and radiated from Miocene to Pleistocene, along with a center of origin in the Irrawaddy-Tsangpo drainages and several rapid speciation in a relatively short time. (c) 2005 Elsevier Inc. All rights reserved.

1.35 mu m photoluminescence from In0.5Ga0.5As/GaAs islands grown by molecular beam epitaxy via cycled (InAs)(1)/(GaAs)(1) monolayer deposition

1.35 mum photoluminescence (PL) with a narrow linewidth of only 19.2 meV at room temperature has been achieved in In0.5Ga0.5As islands structure grown on GaAs (1 0 0) substrate by solid-source molecular beam epitaxy. Atomic force microscopy (AFM) measurement reveals that the 16-ML-thick In0.5Ga0.5As islands show quite uniform InGaAs mounds morphology along the [ 1(1) over bar 0] direction with a periodicity of about 90 nm in the [1 1 0] direction. Compared with the In0.5Ga0.5As alloy quantum well (QW) of the same width, the In0.5Ga0.5As islands structure always shows a lower PL peak energy and narrower full-width at half-maximum (FWHM), also a stronger PL intensity at low excitation power and more efficient confinement of the carriers. Our results provide important information for optimizing the epitaxial structures of 1.3 mum wavelength quantum dots devices. (C) 2000 Elsevier Science B.V. All rights reserved.

硅中Rh-B络合物性质的理论研究

于2010-11-23批量导入

奇奇核170Re在束g谱学和176Ir EC/b+衰变研究

本论文在 166MeV 的束流能量下，利用重离子熔合蒸发反应 142 Nd（32 S， 1p3nγ ）170 Re 布居了 170 Re 的高自旋激发态，用 12 套带 BGO反康普顿抑制的高 纯锗探测器阵列进行了在束 X-γ 和γ γ − 符合测量。在 210MeV 的束流能量下， 利用重离子熔合蒸发反应 146 Nd（35 Cl，5nγ ）176 Ir 产生具有 β+ / EC 衰变性质的 核素 176 Ir, 由氦喷嘴快速带传输系统将反应产物送到低本底区，用一台小平面探 测器、一台轴对称型高纯锗探测器和一台 CLOVER 探测器进行了γ γ − 符合和 t γ − 单谱测量。基于这些测量结果，研究了 170 Re 的高自旋态和 176 Ir 的 β+ / EC 衰变性质。 本工作基于γ−γ符合关系及周围邻近核已知信息的综合分析，首次建立了包 括 16 个能级 26 条γ 跃迁的双奇核 170 Re 的转动带能级纲图，并利用推转壳模型、 粒子转子模型等对其进行了分析和讨论。根据实验提取出的准粒子顺排、 Routhian、旋称劈裂等结构信息和邻近双奇核带结构系统学知识的比较分析，指 出该带的两准粒子组态是 11/213/2 hi π ν ⊗ ，并且该带在低自旋出现旋称反转。 基于对 176 Ir 核 β+ / EC衰变实验数据的离线处理分析，对早先发表的 176 Ir 衰 变γ 跃迁进行确认的同时又发现了 4 个新能级和 13 条新的γ 射线，丰富了 176 Os 核的低位激发态能级纲图。根据典型γ 射线的衰变时间谱建议了 176 Ir核的一个长 寿命低自旋同核异能态，同时通过两准粒子耦合的半经验计算建议了其组态。

Study on the concentration and seasonal variation of inorganic elements in 35 species of marine algae

The concentrations of five major and 28 trace elements in 35 marine algae collected along the coast of China were determined by instrumental neutron activation analysis. The concentrations of halogens, rare earth elements and many transition metal elements in marine algae are remarkably higher than those in terrestrial plants. The concentration factors for 31 elements in all collected algae were calculated, those for tri- and tetra-valent elements were higher than those of the mono- and di-valent elements in marine algae. The biogeochemical characteristics of inorganic elements in marine algae were investigated. In addition, the seasonal variation of inorganic elements in Sargassum kjellmanianum was also studied. (C) 1998 Elsevier Science B.V. All rights reserved.

祁连山海北高寒草甸地区UV-B的气候变化特征

分析祁连山海北高寒草甸地区2002年太阳总辐射（Eg）、UV-B及UV-B占Eg比例的气候变化特征。结果表明：海北站地区UV-B较强，日瞬时最高接近10W•m^-2，日总量最高达0．204MJ•m^-2；日、年变化依Eg的日、年变化具有显著的正相关关系。UV-B与Eg的比值（η），不论是日变化还是年变化表现明显，一日间早晚低，中午高，一年间6月最高，冬季的12月低，与太阳高度角的变化具有一定的正相关关系。年平均η约为0．54％，植物生长期的5～9月约为0．65％。在海北高寒草甸地区Eg和UV-B的年总量分别达6387．436MJ•m^-2和35．981MJ•m^-2。