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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 58 (1987), S. 624-627 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An established method for measuring complex rf magnetic permeability is based on the change in inductance and resistance of a coaxial transmission line upon insertion of a sample toroid. It is not necessary to wind coils on the toroid or correct for geometric demagnetization factors. The use of modern commercial impedance analyzers, as described in this paper, makes measurements from 1 kHz to 1 GHz particularly easy, fast, and accurate.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford BSL : Blackwell Science Ltd
    Molecular microbiology 35 (2000), S. 0 
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: β-1,6-Glucan is an essential fungal-specific component of the Saccharomyces cerevisiae cell wall that interconnects all other wall components into a lattice. Considerable biochemical and genetic effort has been directed at the identification and characterization of the steps involved in its biosynthesis. Structural studies show that the polymer plays a central role in wall structure, attaching mannoproteins via their glycosylphosphatidylinositol (GPI) glycan remnant to β-1,3-glucan and chitin. Genetic approaches have identified genes that upon disruption result in β-1,6-glucan defects of varying severity, often with reduced growth or lethality. These gene products have been localized throughout the secretory pathway and at the cell surface, suggesting a possible biosynthetic route. Current structural and genetic data have therefore allowed the development of models to predict biosynthetic events. Based on knowledge of β-1,3-glucan and chitin synthesis, it is likely that the bulk of β-1,6-glucan polymer synthesis occurs at the cell surface, but requires key prior intracellular events. However, the activity of most of the identified gene products remain unknown, making it unclear to what extent and how directly they contribute to the synthesis of this polymer. With the recent availability of new tools, reagents and methods (including genomics), the field is poised for a convergence of biochemical and genetic methods to identify and characterize the biochemical steps in the synthesis of this polymer.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Candida albicans is the primary fungal pathogen of humans. Despite the need for novel drugs to combat fungal infections [Sobel, J.D. (2000) Clin Infectious Dis 30: 652], antifungal drug discovery is currently limited by both the availability of suitable drug targets and assays to screen corresponding targets. A functional genomics approach based on the diploid C. albicans genome sequence, termed GRACETM (gene replacement and conditional expression), was used to assess gene essentiality through a combination of gene replacement and conditional gene expression. In a systematic application of this approach, we identify 567 essential genes in C. albicans. Interestingly, evaluating the conditional phenotype of all identifiable C. albicans homologues of the Saccharomyces cerevisiae essential gene set [Giaever, G., Chu, A.M., Ni, L., Connelly, C., Riles, L., Veronneau, S., et al. (2002) Nature 418: 387–391] by GRACE revealed only 61% to be essential in C. albicans, emphasizing the importance of performing such studies directly within the pathogen. Construction of this conditional mutant strain collection facilitates large-scale examination of terminal phenotypes of essential genes. This information enables preferred drug targets to be selected from the C. albicans essential gene set by phenotypic information derived both in vitro, such as cidal versus static terminal phenotypes, as well as in vivo through virulence studies using conditional strains in an animal model of infection. In addition, the combination of phenotypic and bioinformatic analyses further improves drug target selection from the C. albicans essential gene set, and their respective conditional mutant strains may be directly used as sensitive whole-cell assays for drug screening.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature genetics 38 (2006), S. 862-863 
    ISSN: 1546-1718
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Medicine
    Notes: [Auszug] Genes do not act in isolation; rather, particular genes interact with one another to modulate cellular systems and generate specific phenotypes. Consequently, mapping of genetic networks is central to our understanding of the function of biological systems and how they can go wrong (for example, in ...
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 10 (1986), S. 587-592 
    ISSN: 1432-0983
    Keywords: Yeast ; Arginine permease ; Membrane protein ; Nucleotide sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The yeast CAN1 gene, thought to encode arginine permease, has found use in genetics as a selectable locus. We have sequenced the cloned CAN1 gene, which contains an open reading frame of 1770 nucleotides, encoding a polypeptide of calculated molecular weight 65,766. Disruption of this open reading frame largely abolishes CAN1 gene expression, while subcloned fragments of the open reading frame hybridize strand —specifically to a 2.3 kb yeast RNA message. The encoded protein has no leader signal sequence, and is highly hydrophobic, with a possible twelve membrane-spanning domains, several of which have the high hydrophobic moments seen in channel-forming or permease proteins. This protein structure is consistent with the CAN1 product being the plasma membrane arginine permease.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 251 (1974), S. 708-710 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Current genetic theory offers at least two explanations for such changes; biological examples of both types are examined in relation to the flax system. (1) Informational nucleic acid may be introduced into flax under the inducing treatments, and be maintained in subsequent generations. Several ...
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Current genetics 9 (1985), S. 285-291 
    ISSN: 1432-0983
    Keywords: Killer toxin ; Plasmid selection ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Transformants of sensitive yeast strains containing an expressed cDNA copy of the yeast killer toxin-immunity gene could be selected for by exposure to added killer toxin. For strain AH-22 the transformation frequency was approximately 10% that obtained by selection for leucine prototrophy. The procedure required time for expression of immunity prior to selection, and a screening step to remove non-transformed survivors. Under conditions where active toxin was produced, transformants containing the toxin-immunity gene were at a selective advantage, and cells losing the plasmid were killed. This resulted in self selection of transformants, and affords a way of maintaining plasmid stability in protrophic strains.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 1432-0983
    Keywords: Oversecretion mutants ; Protease defect ; Wall glucan defect ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two chromosomal mutations in yeast that result in oversecretion of the K1 killer toxin protein were examined. A recessive mutation in gene ski5 appears to lead to toxin oversecretion through a defect in a cell surface, PMSF-inhibited protease. A wild type killer strain degraded toxin following synthesis, and degradation could be partially prevented by addition of PMSF to the growth medium. The ski5 mutation caused an approximate ten fold oversecretion of toxin, similar to that seen in a PMSF-treated wild type culture, and no increased oversecretion in the presence of PMSF. The ski5 mutation caused oversecretion of other low molecular weight secreted proteins and appeared to oversecrete the α-factor pheromone, as judged by activity tests. The ski5 mutation was complemented by mutations in ski genes 1–4, and the mutant was not supersensitive to mating pheromones or K2 killer toxin. We also examined killer strains with a mutation in the nuclear gene krel which results in a defective (1→6)-β-D-glucan cell wall receptor for killer toxin. Such strains oversecrete toxin into the growth medium, but also, unexpectedly, oversecrete most other secreted proteins. The defect in (1→6)-β-D-glucan in these mutants appears to perturb the partitioning of secreted proteins between the cell wall and the medium.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-072X
    Keywords: Transposon mutagenesis ; Soybean ; Nitrogen fixation ; Root nodules ; Auxotrophy ; Bradyrhizobium japonicum ; Glycine ; Rhizobium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four histidine auxotrophs of Bradyrhizobium japonicum strain USDA 122 were isolated by random transposon Tn5 mutagenesis. These mutants arose from different, single transposition events as shown by the comparison of EcoRI and XhoI-generated Tn5 flanking sequences of genomic DNA. The mutants grew on minimal medium supplemented with l-histidine or l-histidinol but failed to grow with l-histidinol phosphate. While two of the muants were symbiotically defective and did not form nodules on Glycine max cvs. Lee and Peking and on Glycine soja, the other two mutants were symbiotically competent. Reversion to prototrophy occurred at a frequency of about 10-7 on growth medium without added antibiotics, but prototrophs could not be isolated from growth medium containing 200 μg/ml kanamycin and streptomycin. The prototrophic revertants formed nodules on all the soybean cultivars examined. When histidine was supplied to the plant growth medium, both nodulation deficient mutants formed effective symbioses. On histidine unamended plants, nodules were observed infrequently. Three classes of bacterial colonies were isolated from such infrequent nodules: class 1 were kanamycin resistant-auxotrophs; class 2 were kanamycin sensitive-prototrophs; and class 3 were kanamycin-sensitive auxotrophs. Our results suggest that two Tn5 insertion mutations in B. japonicum leading to histidine auxotrophy, affect nodulation in some way. These mutations are in regions that show no homology to the Rhizobium meliloti common nodulation genes.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Molecular genetics and genomics 249 (1995), S. 209-216 
    ISSN: 1617-4623
    Keywords: Yeast ; Cell wall ; β-Glucan synthesis ; Kre1p ; O-glycoprotein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The Saccharomyces cerevisiae KRE1 gene encodes a secretory protein required for the production of the cell wall polymer (1 → 6)-β-glucan. Here we report further characterization of the KRE1 gene product, Krelp. A functional, epitope-tagged Krelp is shown to be highly modified in a SEC53-dependent manner. Krelp is O-glycosylated, but the basis for the majority of its post-translational modification is unknown. Fractionation of Kre1p reveals a cell wall-associated form and a less abundant membrane-associated species. Indirect immunoflurorescence demonstrates that Kre1p localizes to the cell surface, where it becomes concentrated at the surface of mother cells. Such a localization of Kre1p seems to parallel the CAL1/CSD2-dependent cell wall deposition of chitin found in S. cerevisiae, and is consistent with evidence from Schizophyllum commune that (1 → 6)-β-glucan accumulates during maturation of the subapical region of the wall distal to the hyphal tip.
    Type of Medium: Electronic Resource
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