Biosynthesis of the fucose-containing xyloglucan nonasaccharide by pea microsomal membranes

Pea microsomal membranes catalyze the transfer of [¹⁴C]fucose (Fuc) from GDP-[U-¹⁴C]fucose, with or without added unlabeled UDP-glucose (Glc), UDP-xylose (Xyl) or UDP-galactose (Gal), to an insoluble product with properties characteristic of xyloglucan. After digestion of the ethanol-insoluble pellet with Streptomyces griseus endocellulase, [¹⁴C] fucose residues occur exclusively in a fragment corresponding in size to the xyloglucan nonasaccharide, Glc₄ Xyl₃ Gal Fuc. This fragment contains a single labeled fucose residue per oligomer, α-linked in a terminal nonreducing position. By comparison, in incubations where GDP-[¹⁴C] fucose is absent and replaced by UDP-[³H]xylose, the maximum size of labeled oligosaccharide found following cellulase digestion of products is an octasaccharide. In the presence of both GDP-[¹⁴C]fucose and UDP-[³H]xylose, a nonasaccharide containing the two labels is produced. Fucose and xylose residues are transferred within a few minutes to acceptor molecules of molecular weight up to 300,000. Such products do not elongate detectably over 60 minutes of incubation. The data support the conclusion that the nonasaccharide subunit of xyloglucan may be generated in vitro by transfucosylation to preformed acceptor chains, and that its synthesis is dependent on the inclusion of exogenous GDP-fucose.     

葡萄糖氧化酶免疫酶染色检测硝酸纤维膜印染的病毒抗原或抗体

<正>近十年来,由于引进了下列技术,包括聚丙烯酰胺凝胶电泳后免疫沉淀、等电聚焦及将样品转移到支持基质的印染技术,分析复杂抗原混合物和其抗体反应的能力显著地提高了。人们已综述了蛋白质印染的一般技术。研究了影响样品经电泳转移到硝酸纤维素(NC)膜上的许多条件。可用同位素或免疫酶方法检测蛋白质印迹。同位素方法很敏感,但较昂贵而配置有些问题,并且有效使用期短。由于同位素法有上述缺点,导致了免疫酶方法的建立。     

抗寄生虫分子疫苗的展望

<正>人们可以预料,预防性疫苗是免疫寄生虫学研究中有实践意义的主要成果。目前正在探索的疫苗是分子疫苗,分子疫苗是由一个或多个有足够长度、结构完整的寄生虫天然分子所组成。分子疫苗主要是预防蠕虫、原虫和节肢动物寄生虫的初次感染或继续感染,亦可预防寄生虫感染引起的严重疾病,其次是降低寄生虫种群在敏感宿主中间的传播率。     

The dependence of protein release from Bacillus amyloliquefaciens on the growth phase in batch culture

For the recovery of intracellular material from bacteria it is often necessary to disrupt the cells. Much work has been done on the kinetics of protein release in beadmills,(1) homogenizers,(2) and by ultrasonication.(3) In this paper we report how the growth phase of Bacillus amyloliquefaciens grown in batch culture affects the rate of protein release by ball milling, ultrasonication, and autolysis. We further suggest that autolysis is a feasible method for disrupting Bacillus.     

A direct fuel cell for the production of electricity from lignin

This report describes the use of an anthraquinone mediated fuel cell for the direct production of electrical energy from sulfonated lignin and Kraft Black Liquor. The cell produces the equivalent of 1 kWh for each 2-3 lb sulfonated lignin and 5-8 lb black liquor combustibles. In the case of the sulfonated lignin, chain session occurs during the oxidation process, reducing the molecular weight from ca. 2 x 10(4) to less than 1000 D.     

Invertase activity of intact cells of Saccharomyces cerevisiae growing on sugar cane molasses. I. Steady-state continuous culture tests

During the steady-state continuous culture of Saccharomyces cerevisiae on sugar cane blackstrap molasses under different experimental conditions, oscillatory variations of the invertase activity of the intact yeast cells were observed. The continuous morphological changes of the cells wall and of the periplasmic space affecting the interaction between invertase and sucrose molecules could be responsible by the observed oscillatory phenomena. The average invertase activity at the steady state is linearly correlated to the cell's growth rate.     

Preparation of Membrane Vesicles Enriched in ATP-Dependent Proton Transport from Suspension Cultures of Tomato Cells

Membranes enriched in ATP-dependent proton transport were prepared from suspension cultures of tomato cells (Lycopersicon esculentum Mill cv VF36). Suspension cultures were a source of large quantities of membranes from rapidly growing, undifferentiated cells. Proton transport activity was assayed as quench of acridine orange fluorescence. The activity of the proton translocating ATPase and of several other membrane enzymes was measured as a function of the cell culture cycle. The relative distribution of the enzymes between the 3,000, 10,000, and 100,000g pellets remained the same throughout the cell culture cycle, but yield of total activity and activity per gram fresh weight with time had a unique profile for each enzyme tested. Maximal yield of the proton translocating ATPase activity was obtained from cells in the middle logarithmic phase of growth, and from 50 to 90% of the activity was found in the 10,000g pellet. The proton translocating ATPase activity was separable from NADPH cytochrome c reductase and cytochrome c oxidase on a sucrose gradient. Proton transport activity had a broad pH optimum (7.0-8.0), was stimulated by KCl with a K_m of 5 to 10 millimolar, stimulation being due to the anion, Cl⁻, and not the cation, K⁺, and was not inhibited by vanadate, but was inhibited by NO₃⁻. The activity is tentatively identified as the tonoplast ATPase.     

Abscisic Acid and cutout in cotton

A decline in growth, flowering, and boll (fruit) retention is referred to as cutout in cotton (Gossypium hirsutum L.). Fruit load affects cutout, possibly through hormonal effects. Experiments were conducted to test the hypothesis that fruits are a source of abscisic acid (ABA) that moves into fruiting branches and growing points where it inhibits growth, flowering, and boll retention. Removal of the flower or young boll at the first node of fruiting branches did not decrease the ABA content of fruiting branches or the abscission zone at the second node. Effects on ABA content of the boll at the second node varied. In one field test, ABA content of bolls at the second node decreased with successive harvests as bolls were removed from first node positions of several fruiting branches. Thus, the effect was cumulative and was not limited to individual branches. Removal of the flower or boll at the first node increased boll retention at the second node. Removal of all flowers during the first 3 weeks of flowering delayed the decreases in growth, flowering, and boll retention that occurred as fruit load increased. But, the ABA content of fruiting branches and mainstem apices was not decreased by early defruiting and did not increase with increasing fruit load. The results do not support the hypothesis that fruits are a source of ABA that moves into fruiting branches and growing points where it then inhibits growth, flowering, and boll retention.     

Free space iron pools in roots: generation and mobilization

A rapid and simple method for the determination of a ferric iron pool in the free space of roots is described. Formation of this pool depended on the source of iron in the nutrient solution. During growth in water culture at pH 5 to 6 with Fe-ethylenediaminetetraacetate, a free space pool of 500 to 1000 nanomoles Fe per gram fresh weight was formed in the roots of bean (Phaseolus vulgaris L. var. Prélude), maize (Zea mays L. var. Capella), and chlorophytum (Chlorophytum comosum [Thunb.] Jacques). No significant pool (less than 100 nanomoles per gram fresh weight) was formed with ferrioxamine. Upon impending Fe deficiency, bean and chlorophytum were able to mobilize this pool. Fe-deficient bean plants mobilized iron from the free space iron pool of another plant in the same vessel.     

ADP Is a Competitive Inhibitor of ATP-Dependent H Transport in Microsomal Membranes from Zea mays L. Coleoptiles

An anion-sensitive ATP-dependent H⁺ transport in microsomal membranes from Zea mays L. coleoptiles was partially characterized using the pH gradient-dependent decrease of unprotonated neutral red. The following criteria strongly suggest a tonoplast origin of the H⁺ transport observed: strict dependence on Cl⁻; inhibition by SO₄²⁻ and NO₃⁻; insensitivity against vanadate, molybdate, and azide; reversible inhibition by CaCl₂ (H⁺/Ca²⁺ antiport); inhibition by diethylstilbestrol. The substrate kinetics revealed simple Michaelis Menten kinetics for ATP in the presence of 1 millimolar MgCl₂ with a K_m value of 0.56 millimolar (0.38 millimolar for MgATP). AMP and c-AMP did not influence H⁺ transport significantly. However, ADP was a potent competitive inhibitor with a K_i value of 0.18 millimolar. The same inhibition type was found for membranes prepared from primary roots by the same procedure.