稻茎毛眼水蝇幼虫田间分布型及抽样技术

根据14丘稻田稻茎毛眼水蝇幼虫调查资料．对其幼虫分布型进行了分析。结果表明;用I、CAm／m、Iσ四种聚集指标法测定,64．3％的田块呈随机分布．28．4%为均匀分布．7．3%为聚集分布。用Iwao平均拥挤度和Taylor幂法则测定．其田间分布型符合随机分布。用频次拟合法测验,50%的田块同时符合渡松、奈曼和负二项分布三种分布型;35．7%的田块同时符合2种分布型。根据该虫田间分布型的特点．制定了相应的序贯抽样技术。     

CaM BP－10对NAD激酶的抑制效应

ＮＡＤ激酶在光合作用等植物生理过程中起重要作用。ＮＡＤ激酶的激活依赖于钙离子和钙调素（ＣａｌｍＯｄｕｌｉｎ,ＣａＭ）．从植物中分离得到的一种新的ＣａＭ结合蛋白ＣａＭＢＰ－１０（ＢＰ－１０）明显抑制ＮＡＤ激酶的激活活性,抑制作用可被ＣａＭ所克服．动力学研究表明,抑制效应是ＢＰ－１０与ＣａＭ之间特异性相互作用的结果。实验证实ＢＰ－１０对ＮＡＤ激酶活性起着重要调节作用．     

Two Phenol Sulfotransferase Species from One cDNA: Nature of the Differences

A phenol sulfotransferase from rat liver (EC 2.8.2.9), expressed inEscherichia colifrom a single cDNA, was purified as two separable but catalytically active proteins. The proteins appeared to be identical to each other and to the natural liver sulfotransferase by comparison of their amino acid constitution, amino-terminal end group, and interaction with a polyclonal antibody raised against the liver enzyme. Each of the recombinant forms, α and β, catalyzed the sulfuryl group transfer from 4-nitrophenylsulfate to an acceptor phenol, a reaction in which 3′-phospho-adenosine 5′-phosphate (PAP) is a necessary intermediate. Only form β, however, catalyzes the physiological transfer of a sulfuryl group from 3′-phosphoadenosine 5′-phosphosulfate (PAPS) to the free phenol. Evidence is presented that sulfotransferase α, but not β, has 1 mol of PAP tightly bound per enzyme dimer. The ability to utilize PAPS as a sulfate donor could be altered: form α could be treated and purified as form β to acquire the ability to use PAPS, whereas form β was treated by extended incubation with PAP, lost its ability to use PAPS, and was purified as form α.     

Phospholipid surface density determines the partitioning and permeability of acetic acid in DMPC:cholesterol bilayers

Relationships between the permeability coefficient (P_HA) and partition coefficient (K _m/w) of acetic acid and the surface density of DMPC:cholesterol bilayers have been investigated. Permeability coefficients were measured in large unilamellar vesicles by NMR line broadening. Bilayer surface density, , was varied over a range of 0.5–0.9 by changing cholesterol concentration and temperature. The temperature dependence of P_HA for acetic acid exhibits Arrhenius behavior with an average apparent activation energy (E _a ) of 22±3 kcal/mole over a cholesterol mole fraction range of 0.00–0.40. This value is much greater than the enthalpy change for acetic acid partitioning between bulk decane and water (H° = 4.8±0.8 kcal/mole) and the calculated E _a (= 8.0 kcal/mole) assuming a bulk phase permeability model which includes the enthalpy of transfer from water to decane and the temperature dependence of acetic acid's diffusion coefficient in decane. These results suggest that dehydration, previously considered to be a dominant component, is a minor factor in determining E _a . Values of 1n P_HA decrease linearly with the normalized phospholipid surface density with a slope of = -12.4±1.1 (r = 0.90). Correction of P_HA for those temperature effects considered to be independent of lipid chain order (i.e., enthalpy of transfer from water to decane and activation energy for diffusion in bulk hydrocarbon) yielded an improved correlation ( = -11.7±0.5 (r = 0.96)). The temperature dependence of K_m/w is substantially smaller than that for P_HA and dependent on cholesterol composition. Values of 1n K_m/w decrease linearly with the surface density with a slope of = -4.6±0.3 (r = 0.95), which is 2.7-fold smaller than the slope of the plot of 1n P_HA vs. . Thus, chain ordering is a major determinant for molecular partitioning into and transport across lipid bilayers, regardless of whether it is varied by lipid composition or temperature.This work was supported by grants from Glaxo, INTERx/Merck, and University of Utah Research Committee.     

Two-dimensional crystallization of avidin on biotinylated lipid monolayers.

Two-dimensional crystals of avidin were obtained on mixed lipid monolayers containing biotinylated lipids (N-biotinyl-dipalmitoyl-L-alpha-phosphatidyl ethanolamine and dioleoyl phosphatidyl choline) by specific interaction. Image analysis of electron micrographs of these crystals revealed p2 symmetry with the unit cell parameters a = 66 +/- 2 A, b = 68 +/- 1 A, and gamma = 121 +/- 4 degrees. The projection map showed, at a resolution of about 27 A, that the four subunits within one avidin molecule are separated into two parts. Comparison between avidin and streptavidin reveals that avidin molecule binds to the lipid monolayer in an orientation similar to that of streptavidin.     

Analysis of serine/threonine-linked oligosaccharides derived by alkaline-borohydride treatment of mucin glycoproteins electroblotted onto membranes: comparison of the saccharide profiles of the 390 kDa and 350 kDa forms of epitectin

Alkaline borohydride treatment is widely used for the release of carbohydrate moieties from O-glycosylated glycoproteins and mucins. We have adapted this procedure to micro quantities of glycoproteins blotted on membranes. After electrophoresis and transfer to nitrocellulose, nylon or polyvinylidene difluoride membrane, alkaline borohydride treatment was done directly on glycoprotein containing areas of membrane which were cut out with the aid of guide strips stained with Coomassie Blue or lectin-digoxigenin. In combination with standard saccharide fractionation techniques, this procedure can be used to characterize the oligosaccharides of mucins or mucin-type glycoproteins that are separated by gel electrophoresis from crude sources. Using this approach we have characterized the saccharides derived from the two species of epitectin, a malignancy-associated mucin type glycoprotein, isolated from metabolically labelled H.Ep2 cells.     

甘蔗和烟草幼叶原生质体的核酸含量与核酸酶活性及其影响因素

与幼叶组织相比,酶法新鲜分离的甘蔗和烟草幼叶原生质体内的ＲＮＡ、ＤＮＡ及总核酸含量均降低。其原因可能是刚游离的原生质体内酸性和碱性ＲＮＡ酶与ＤＮＡ酶等活性提高所致。甘蔗叶原生质体内的核酸降低量和ＲＮＡ酶与ＤＮＡ酶活性的增加程度均高于烟草。随用作渗透压稳定剂的甘露醇浓度增加,甘蔗和烟草叶原生质体的ＲＮＡ酶和ＤＮＡ酶活性均相应提高。其中以甘蔗叶原生质体的核酸酶活性增加水平较明显。在细胞壁降解产物的作用下,除了甘蔗原生质体内的ＲＮＡ酶活性略被促进外,其ＤＮＡ酶和烟草叶原生质体内的核酸酶均不受影响     

Characterization of the oriC region of Mycobacterium smegmatis.

A 3.5-kb DNA fragment containing the dnaA region of Mycobacterium smegmatis has been hypothesized to be the chromosomal origin of replication or oriC (M. Rajagopalan et al., J. Bacteriol. 177:6527-6535, 1995). This region included the rpmH gene, the dnaA gene, and a major portion of the dnaN gene as well as the rpmH-dnaA and dnaA-dnaN intergenic regions. Deletion analyses of this region revealed that a 531-bp DNA fragment from the dnaA-dnaN intergenic region was sufficient to exhibit oriC activity, while a 495-bp fragment from the same region failed to exhibit oriC activity. The oriC activities of plasmids containing the 531-bp sequence was less than the activities of those containing the entire dnaA region, suggesting that the regions flanking the 531-bp sequence stimulated oriC activity. The 531-bp region contained several putative nine-nucleotide DnaA-protein recognition sequences [TT(G/C)TCCACA] and a single 11-nucleotide AT-rich cluster. Replacement of adenine with guanine at position 9 in five of the putative DnaA boxes decreased oriC activity. Mutations at other positions in two of the DnaA boxes also decreased oriC activity. Deletion of the 11-nucleotide AT-rich cluster completely abolished oriC activity. These data indicate that the designated DnaA boxes and the AT-rich cluster of the M. smegmatis dnaA-dnaN intergenic region are essential for oriC activity. We suggest that M. smegmatis oriC replication could involve interactions of the DnaA protein with the putative DnaA boxes as well as with the AT-rich cluster.     

长萼木通属——木通科一新属

缺瓣牛姆瓜Holboellia apetala Q．Xia,J．Z.Suen et Z．X．Peng在一系列特征上与牛姆瓜属Holboellia植物不同,不应隶属于该属,而代表了一个未被描述过的新属—长萼木通属。新属在茎、叶、果实和花的大部分特征上与木通属Akebia相似,但花萼特征又与野木瓜属Stauntonia接近,其系统位置介于这两个属之间,并偏于前者。     

薏苡胚乳传递细胞的超微结构

传粉后１０ ｄ,薏苡（Ｃｏｉｘ ｌａｃｒｙｍ ａ－ｊｏｂｉＬ．）颖果基部胚乳最外层传递细胞具长而多的壁内突,第二层细胞的壁内突较第一层的短而少,均具瓣裂的细胞核、丰富的线粒体、粗糙内质网、核糖体、产生小泡的高尔基体及与壁内突质膜相连的、含深色物质的囊泡。线粒体分布于壁内突附近或其间。授粉后２５ ｄ,第一、二层细胞壁内突发达,几乎充满了细胞,但细胞器可见。第四层传递细胞具树枝状及网状的壁内突,大量线粒体、具质体膜的淀粉粒、脂体存在壁内突附近或壁内突的间隙内。高尔基体常见,仅见很少的片段内质网。第五层传递细胞具短的壁内突、较大的淀粉粒及许多小蛋白质体。两个时期的第一、二层细胞内均未观察到胞间连丝。授粉后２５ ｄ,第四层及以上的传递细胞的细胞壁和呈网状的壁内突均含有胞间连丝。还讨论了各种细胞器的作用及各层传递细胞的功能