蓝细菌6803agp基因的分子克隆和缺失突变株的构建

PCR扩增了蓝细菌集胞藻6803(Synechocystis sp.PCC6803)的agp基因（编码ADP－葡萄糖焦磷酸羧化酶）,进一步以pUC118为载体将其克隆到大肠杆菌中,构建了pUCA质粒。通过DNA体外重组,以红霉素抗性基因部分取代agp基因片段,构建了既含agp基因上游及下游序列、又携带选择性标记－红霉素抗性的pUCAE质粒。该质粒转化野生型集胞藻6803细胞,获得了能在含红霉素的培养基上正常生长的agp基因缺失突变株。对该突变株基因组DNA进行PCR扩增,验邝了其基因结构的正确性。突变株细胞生长速度较野生型细胞快,胞内的叶绿素含量比野生型细胞高,表明该突变株具有较高的光合效率。在突变株中未检测到糖原的存在,进一步从生理水平上验证了突变株构建的正确性。     

多头绒泡菌银染核仁周期的电镜研究

以同步化培养的多头绒泡菌（Physarum poldycephalum Schw.)原生质团为材料,应用整体银染技术,电镜下研究了核仁在细胞周期中的超微结构变化。结果变化：核仁成熟时比较大,位于细胞核中央,核仁内可区分出纤维中心、密集纤维成分和颗粒成分等。前期时,核仁向边缘移动,前期末在近核膜处解体,解体的核仁物质主要呈团块状散开。中期时,解体的核仁物质位于细胞核中央染色体区域的周围,染色体上没有特异的银染区域,染色体周边也看不到银染的“鞘”状结构,但在染色体中可见一些散在的银染大颗粒。末期时,核仁物质与染色体一起到达两极,在子细胞核中与正在解集缩的染色质共存一起,以后核仁物质逐渐汇合并与染色质分开。大约在有丝分裂结束120min后,在细胞核中形成一候 中央位置的大核仁,结果提示,低等真核生物的核仁结构和周期变化与高等真核生物的不完全相同。     

UV—B辐射对大豆生长、产量和稳定碳同位素组成的影响

大田条件下,模拟20%的平流层臭氧层衰减时辐射到地表的紫外线B（UV-B,280-320nm)的增强。研究了10个大豆（Glycine max(L.)Merr.)品种根、茎、叶和种子的稳定碳同位素组成（δ^13C)、生物量、产量和收获指数的变化。UV-B辐射增加使所有品种的总生物量和产量分别平均下降24.2%和23.3%,10个品种的收获指数平均提高1.39%,其中6个品种的收获指数增加,4个减少。与对照相比,UV-B作用下9个品种叶、茎、根和种子中稳定碳同位素（δ^13C值）组成降低,一个品种“8907-32”各器官稳定碳同位素组成增加。δ^13C值存在器官差异。10个品种的对照组和处理组的δ^13C平均值由大到小的顺序是根、茎、种子和叶。结果表明,UV-B可能导致大豆代谢过程及代谢产物的分配发生变化。     

问荆中三个新的酚甙化合物

从问荆（Equisetum arvense L.)营养茎的水溶性成分中分离到１２个化合物。经波谱解析和化学方法鉴定。其中３个新的酚甙化合物分别命名为equisetumosideA(3-methoxy-11,12-dihydroxy-phenylhexane-9-one-4-O-β－Ｄglucopyra-noside)、equisetumoside B(3-methoxy-4,11-dihdroxy-phenylhexane-9-one-12-O-β－Ｄ－glucopyranoside)和equisetumosideＣ（cis-ferulic acid potassium salt 4-O-β－Ｄ－glucopyranoside);其他成分鉴定为尿甙、次黄甙、２′－脱氧次黄甙、２′－脱氧胞甙、色氨酸、胸甙、５－羟基－２′－脱氧尿甙、松柏甙和莰非醇－３－O-β－Ｄ－槐糖基 －７－O-β－Ｄ－吡喃葡萄糖甙。这些化合物均为首次从该植物中分离得到。     

新化合物柴胡皂甙q-1的结构鉴定(英文)

从北柴胡 (BupleurumchinenseDC .)根的醇提液的正丁醇部分分离得到 3个化合物 ,分别鉴定为柴胡皂甙q_1(1)、3″_O_乙酰柴胡皂甙d (2 )和 3″_O_乙酰柴胡皂甙b2 (3)。化合物 1为新化合物 ,用化学和波谱法确定其结构为3β,16α ,2 3,2 8,30_五羟基_齐墩果_11,13(18)_二烯_3_O_β_D_吡喃葡萄糖基 (1→ 6 )_[α_L_吡喃鼠李糖基 (1→ 4) ]_β_D_吡喃葡萄糖甙。化合物 2和 3为首次从北柴胡中分离得到。     

Flexible polymer TiO2 modified film photocatalysts active in the photodegradation of azo-dyes in solution

This review summarizes the recent developments of thin film polymer coated photocatalysis with TiO₂ mediating the discoloration/degradation of the azo-dye Orange II under light irradiation. The stable anchoring of TiO₂ on non-heat resistant but chemically inert flexible polymer films is described. The nature of the polymer films used, the pretreatment of the film for the TiO₂ loading and the testing of the photocatalytic activity are addressed for different inert polymer films not having the conventional functional surface groups to bind TiO₂. The discoloration of Orange II in the presence of LDPE/TiO₂ is completed in about 10 h. This is a significantly longer times than the one observed for the same process when Tedlar/TiO₂ and Parylene/TiO₂ were used in the dye discoloration process. This points out to specific effects particular to each the polymer support used to graft the photoactive TiO₂ particles.     

Isothermal titration calorimetry of metal ions binding to proteins: An overview of recent studies

Isothermal titration calorimetry (ITC) is a technique that is capable of quantifying the stoichiometry, equilibrium constants and thermodynamics of molecular binding events. Thus, important information about the interaction of metal ions with biological macromolecules can be obtained with ITC measurements. This review highlights many of the recent studies of metal ions binding to proteins that have used ITC to quantify the thermodynamics of metal-protein interactions.     

Age-Associated Alterations of the Mitochondrial Genome

Age-associated alterations of the mitochondrial genome occur in several different species; however, their physiological relevance remains unclear. The age-associated changes of mitochondrial DNA (mtDNA) include nucleotide point mutations and modifications, as well as deletions. In this review, we summarize the current literature on age-associated mtDNA mutations and deletions and comment on their abundance. A clear need exists for a more thorough evaluation of the total damage to the mitochondrial genome that accumulates in aged tissues. © 1997 Elsevier Science Inc.     

Gene silencing: Cosuppression at a distance

When a plant carries a transgenic copy of an endogenous gene, both genes may be silenced. This ‘cosuppression’ can occur not only within individual cells, but also in distant cells through an agent that apparently moves through the plant's phloem.     

PDZ domain proteins: Scaffolds for signaling complexes

InaD, a Drosophila photoreceptor scaffolding protein, assembles multiple signal-transducing proteins at the membrane via its five PDZ domains, enhancing speed and efficiency of vision. Extensive conservation of PDZ domains suggests that these motifs have a general role in organizing diverse signaling complexes.