20-羟基蜕皮酮对蓖麻蚕蛹体液免疫的调节作用(英)

本研究指出20—羟基蜕皮酮(20-OHE)参加蓖麻蚕蛹对大肠杆菌的体液免疫反应。20-OHE的作用方式是多方面的,包括提高血淋巴蛋白质含量,产生抗菌蛋白,增加溶菌酶活性,和激活原酚氧化酶系统。这表明多个免疫控制系统参与蓖麻蚕蛹体液免疫反应的可能性。     

新型气升式反应器在发酵培养中的应用研究

本文以Ｌ－苹果酸生产为例,采用新型的分段内循环气升式反应器分批培养产延胡索酸酶的产氨短杆菌ＭＡ－２,并与同等规模机械搅拌反应器中接着的结果相比较。数据表明,采用气升式发酵设备进行培养,该菌体的收率能提高近３％,且发酵周期能缩短一半左右,显著降低培养成本,该类型的反应器具有广阔的应用前景。     

马铃薯人工种子的研究

本研究以虎头（Ｈ）、克四（Ｋ）和Ｆａｖｏｒｉｔａ（Ｆ）三个品种的马铃薯不定芽在液体培养条件下诱导生成的微型薯为试材,经筛选后获得的大小一致的微型薯经过适度的低温处理后,用４％的海藻酸钠和２％的氯化钙溶液,在附加一定的植物激素条件下,进行人。种皮包埋形成人工种子。在无菌条件下,三个品种的人工种子萌发率均达９０％以上。在土壤中,人工种子萌发率可达６０％以上,萌发的人工种子中８０％能够形成生长发育正常的完整植株。     

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.     

REGULATORY ROLE OF 20-HYDROXYECDYSONE ON HUMORAL IMMUNITY IN THE PUPAE OF THE INDIAN SILKWORM,PHZLOSAMIA CYNTHIA RICINI*

Abstract The present study shows that 20-hydroxyecdysone(20-OHE) participates in the humoral immune responses of Philosamia Cynthia ricini, either normal or debrained pupae, to the E. coli. The mode of action of 20—-OHE is multiple. It raises hemolymph protein content, makes antibacterial proteins be produced, increases lysozyme activity, and activates prophenoloxidase system. It is possible that several immune control systems are involved.     

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.     

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     

Three-dimensional structure prediction of the NAD binding site of proton-pumping transhydrogenase from Escherichia coli

A three-dimensional structure of the NAD site of Escerichia coli transhydrogenase has been predicted. The model is based on analysis of conserved residues among the transhydrogenases from five different sources, homologies with enzymes using NAD as cofactors or substrates, hydrophilicity profiles, and secondary structure predictions. The present model supports the hypothesis that there is one binding site, located relatively close to the N-terminus of the α-subunit. The proposed structure spans residues α145 to α287, and it includes five β-strands and five α-helices oriented in a typical open twisted α/β conformation. The amino acid sequence following the GXGXXG dinucleotide binding consensus sequence (residues α172 to α177) correlates exactly to a typical fingerprint region for ADP binding βαβ folds in dinucleotide binding enzymes. In the model, aspartic acid α195 forms hydrogen bonds to one or both hydroxyl groups on the adenosine ribose sugar moiety. Threonine α196 and alanine α256, located at the end of βB and βD, respectively, create a hydrophobic sandwich with the adenine part of NAD buried inside. The nicotinamide part is located in a hydrophobic cleft between αA and βE. Mutagenesis work has been carried out in order to test the predicted model and to determine whether residues within this domain are important for proton pumping directly. All data support the predicted structure, and no residue crucial for proton pumping Was detected. Since no three-dimensional structure of transhydrogenase has been solved, a well based tertiary structure prediction is of great value for further experimental design in trying to elucidate the mechanism of the energy-linked proton pump. © 1995 Wiley-Liss, Inc.