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We describe here a simple, general procedure for the purification of a variety of lectins, and for the preparation of lectin-ferritin conjugates of defined molar composition and binding properties to be used as probes for cell surface saccharides. The technique uses a “universal” affinity column for lectins and their conjugates, which consists of hog sulfated gastric mucin glycopeptides covalently coupled to agarose. The procedure involes: (a) purification of lectins by chromatography of aqueous extracts of seeds or other lectin-containing fluids over the affinity column, followed by desorption of the desired lectin with its hapten suge; (b) iodination of the lectin to serve as a marker during subsequent steps; (c) conjugation of lectin to ferritin with glutaraldehyde; (d) collection of active lectin-ferritin conjugates by affinity chromatography; and (e) separation of monomeric lectin-ferritin conjugates from larger aggregates and unconjugated lectin by gel chromatography. Based on radioactivity and absorbancy at 310 nm for lectin and ferritin, respectively, the conjugates consist of one to two molecules of lectin per ferrritin molecule. Binding studies of native lectins and their ferritin conjugates to dispersed pancreatic acinar cells showed that the conjugation procedure does not significantly alter either the affinity constant of the lectin for its receptor on the cell surface or the number of sites detected. 相似文献
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High-throughput approaches are beginning to have an impact on many areas of yeast biology. Two recent studies, using different experimental platforms, provide insight into new pathways involved in the response of yeast to DNA damage. 相似文献
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The tomato Cf-9 disease resistance gene functions in tobacco and potato to confer responsiveness to the fungal avirulence gene product avr 9 总被引:12,自引:0,他引:12 下载免费PDF全文
The Cf-9 gene encodes an extracytoplasmic leucine-rich repeat protein that confers resistance in tomato to races of the fungus Cladosporium fulvum that express the corresponding avirulence gene Avr 9. We investigated whether the genomic Cf-9 gene functions in potato and tobacco. Transgenic tobacco and potato plants carrying Cf-9 exhibit a rapid hypersensitive cell death response (HR) to Avr 9 peptide injection. Cf 9 tobacco plants were reciprocally crossed to Avr 9-producing tobacco. A developmentally regulated seedling lethal phenotype occurred in F1 progeny when Cf9 was used as the male parent and Avr 9 as the female parent. However, when Cf9 was inherited in the maternal tissue and a heterozygous Avr 9 plant was used as the pollen donor, a much earlier reaction was caused, leading to no germination of any F1 seed. Detailed analysis of the Avr 9-induced responses in Cf 9 tobacco leaves revealed that (1) most mesophyll cells died within 3 hr (compared with 12 to 16 hr in tomato); (2) the macroscopic HR was visible at an Avr 9 titer five times lower than that which caused visible symptoms in tomato; (3) the HR invariably extended into noninjected panels of the tobacco leaf; (4) no HR occurred in leaves of young tobacco plants; (5) in older plants, the HR was dramatically enhanced by sequential Avr 9 challenges; and (6) coexpression of a salicylate hydroxylase transgene (nahG) from Pseudomonas putida reduced the severity of the macroscopic leaf HR and also restored germination to Cf 9 x 35S:Avr 9 F1 seedlings. Simultaneous introduction of Cf-9 homologs (Hcr 9-9 genes A and B or D) along with the native Cf-9 gene did not alter the responses that were specifically induced by Avr 9. Various ways to use the Cf-9-Avr 9 gene combination to engineer broad-spectrum disease resistance in several solanaceous species are discussed. 相似文献
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Predicting shorebird mortality and population size under different regimes of shellfishery management 总被引:6,自引:0,他引:6
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The spatial variations in the densities of adult (>1 year old) musselsMytilus edulis L. in the Exe estuary, South-west England, are investigated in relation to six potentially significant environmental gradients;
distance up-estuary and up-shore, substrate softness, mussel bed topography, bed area and proportion covered by algae. The
most important correlate of mussel density was the up-shore gradient, as measured by exposure time; mussels were densest just
below mid-tide level. The level of recruitment of spat mussels (O yr) to each bed depended on the densities of adults already
present; more spat were recruited where adults were denser. Their subsequent mortality was strongly density dependent, with
the numbers surviving the winter also being related to the density of adults. Hence the population as a whole was self-sustaining
and densities on the individual beds were related to the up-shore gradient of exposure time. The question of how adult densities
became established in the first place is therefore discussed. In former times, fishermen laid many mussel beds over the estuary
and it is concluded that, once abandoned, only those placed at or below the mid-tide level survived. 相似文献
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Ponnappan RK Markova DZ Antonio PJ Murray HB Vaccaro AR Shapiro IM Anderson DG Albert TJ Risbud MV 《Arthritis research & therapy》2011,13(5):R171