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  • 1
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Journal of the American Chemical Society 86 (1964), S. 694-696 
    ISSN: 1520-5126
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 2
    Digitale Medien
    Digitale Medien
    s.l. : American Chemical Society
    Journal of medicinal chemistry 18 (1975), S. 1159-1161 
    ISSN: 1520-4804
    Quelle: ACS Legacy Archives
    Thema: Chemie und Pharmazie
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 91 (2002), S. 6007-6014 
    ISSN: 1089-7550
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: This article describes the admittance-frequency feature of a class of SnO2⋅CoO-based polycrystalline ceramics with high nonlinear current–voltage characteristics (nonlinear coefficients above 50). Broad relaxation peaks caused by the presence of deep trap states were characterized based on the admittance response of different systems doped with La2O3, Pr2O3, and CeO2. The calculation of the energy of this deep trap level revealed not only that all the compositions share the same value but also that this value could be attributed to an oxygen vacancy or to CoSn[partial lengthening] like defects. The values of barrier height and density of states obtained from a capacitance–voltage analysis are in good agreement with the nonlinear coefficients. The highest nonlinear coefficients are found in compositions with greater barrier height values and higher density of deep trap states at the grain boundary interface. © 2002 American Institute of Physics.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 79 (2001), S. 48-50 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: A model is proposed here to explain how the chemical features of metal oxide varistors can alter their nonohmic physical behavior, based on nonohmic similarities in the electrical properties of ZnO- and SnO2-based varistors. The proposed model explains the electrical properties of ZnO- and SnO2-based varistors before and after thermal treatments in oxygen- and nitrogen-rich atmospheres, which cause similar changes in the nonohmic feature of these polycrystalline ceramics with greatly differing chemical compositions and microstructures. The model is based on the key role that oxygen plays in varistor grain boundaries, independently of the type of ceramic system (ZnO-, SnO2- or even SrTiO3-based varistors) involved. © 2001 American Institute of Physics.
    Materialart: Digitale Medien
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Molecular genetics and genomics 263 (2000), S. 925-933 
    ISSN: 1617-4623
    Schlagwort(e): Key words S-like RNase ; Phosphate starvation ; Senescence ; RFLP ; Almond
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract A cDNA for an S-like RNase (RNase PD2) has been isolated from a pistil cDNA library of Prunus dulcis cv. Ferragnés. The cDNA encodes an acidic protein of 226 amino acid residues with a molecular weight of 25 kDa. A potential N-glycosylation site is present at the N-terminus in RNase PD2. A signal peptide of 23 amino acid residues and a transmembrane domain are predicted. The two active-site histidines present in enzymes of the T2/S RNase superfamily were detected in RNase PD2. Its amino acid sequence shows 71.2% similarity to RNS1 of Arabidopsis and RNase T2 of chickpea, respectively. Northern blotting and RT-PCR analyses indicate that PD2 is expressed predominantly in petals, pistils of open flowers and leaves of the almond tree. Analyses of shoots cultured in vitro suggested that the expression of RNase PD2 is associated with phosphate starvation. Southern analysis detected two sequences related to RNase PD2 in the P. dulcis genome. RFLP analysis showed that S-like RNase genes are polymorphic in different almond cultivars. The PD2 gene sequence was amplified by PCR and two introns were shown to interrupt the coding region. Based on sequence analysis, we have defined three classes of S-like RNase genes, with the PD2 RNase gene representing a distinct class. The significance of the structural divergence of S-like RNase genes is further discussed.
    Materialart: Digitale Medien
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Plant cell reports 19 (2000), S. 1108-1114 
    ISSN: 1432-203X
    Schlagwort(e): Key words Almond ; cDNA cloning ; Prunus dulcis Sequence comparison ; S-like RNase
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract  Many flowering plants contain stylar S-RNases that are involved in self-incompatibility and S-like RNases of which the biological function is uncertain. This paper reports the deduced amino acid sequence of an S-like RNase gene (PD1) from the self-incompatible plant Prunus dulcis (almond). The amino acid sequence of PD1, which was derived from cDNA and genomic DNA clones, showed 34–86% identity to acidic plant S-like RNases reported so far, with the highest degree of similarity being to an S-like RNase from Japanese pear (Pyrus pyrifolia). Based on RNA hybridisation experiments it appears that, like for many other S-like RNases, the expression of PD1 is not pistil-specific. Analysis of the genomic structure revealed the presence of three introns, of which one is similar in location to that of the related S-RNase gene from Solanaceae and Rosaceae. At least four bands hybridising to PD1 were found upon Southern hybridisation, suggesting the presence of a multigene family of S-like RNase genes in almond. The putative biological function of PD1 is discussed.
    Materialart: Digitale Medien
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Plant cell reports 18 (1999), S. 387-393 
    ISSN: 1432-203X
    Schlagwort(e): Key words Almond ; Prunus ; Transformation ; Agrobacterium ; Adventitious regeneration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Almond (Prunus dulcis Mill.) leaves were transformed with the marker genes gusA (β-glucuronidase) and nptII (neomycin phosphotransferase II) via Agrobacterium-mediated transformation. Bacterial strains and preculture of explants affected efficiency of gene transfer evaluated by transient expression assays. Following transformation, shoots were induced from primary explants on medium without kanamycin and exposed to selection 20 days after cocultivation. From 1419 original leaves, four shoots (A, B, C and D) were obtained that showed amplification of the predicted DNA fragments by polymerase chain reaction (PCR). After micropropagation of these shoots, only those cloned from shoot D gave consistently positive results in histochemical GUS detection and PCR amplification. Southern blot hybridisation confirmed stable transgene integration in clone D, which was also negative in PCR amplification of an Agrobacterium gene. Additional molecular analysis suggested that the remaining three shoots (A, B and C) were chimeric.
    Materialart: Digitale Medien
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  • 8
    ISSN: 1432-2242
    Schlagwort(e): Electric field-induced microfusion ; Microculture ; Nicotiana ; Somatic hybridization ; Cytoplasmic male sterility
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Somatic hybrid/cybrid plants were obtained by microfusion of defined protoplast pairs from malefertile, streptomycin-resistant Nicotiana tabacum and cytoplasmic male-sterile (cms), streptomycin-sensitive N. tabacum cms (N. bigelovii) after microculture of recovered fusants. Genetic and molecular characterization of the organelle composition of 30 somatic hybrid/cybrid plants was performed. The fate of chloroplasts was assessed by an in vivo assay for streptomycin resistance/ sensitivity using leaf explants (R0 generation and R1 seedlings). For the analysis of the mitochondrial (mt) DNA, species-specific patterns were generated by Southern hybridization of restriction endonuclease digests of total DNA and mtDNA, with three DNA probes of N. sylvestris mitochondrial origin. In addition, detailed histological and scanning electron microscopy studies on flower ontogeny were performed for representative somatic hybrids/cybrids showing interesting flower morphology. The present study demonstrates that electrofusion of individually selected pairs of protoplasts (microfusion) can be used for the controlled somatic hybridization of higher plants.
    Materialart: Digitale Medien
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  • 9
    ISSN: 1432-2145
    Schlagwort(e): Nicotiana ; Cytoplasmic male sterility ; Flower morphogenesis ; mtDNA organization ; In organello protein synthesis ; Mitochondrial transcripts
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary A detailed description of in planta floral ontogeny based on scanning electron microscopy, developmental histology and morphology is presented for three different alloplasmic gene-cytoplasmic male-sterile (CMS)Nicotiana tabacum isonuclear lines with cytoplasms ofN. bigelovii, N. debneyi and N. suaveolens and compared to the corresponding nuclear donorN. tabacum genotype. This allowed the precise determination of the developmental stages affected in the mutant forms as well as a thorough phenotypic characterization of them. The organization of the mitochondrial genome and expression of mitochondrial DNA (mtDNA) was investigated in the three different alloplasmic CMS tobacco analogs and compared to the corresponding malefertile parentalNicotiana species. Southern hybridizations of total cellular DNA and mtDNA from the different sets of lines with probes specific for mitochondrial genes coding for cytochrome oxidase subunits I, II and III, apocytochrome b, ATPase subunits α and 9 as well as 18S-5S ribosomal RNA indicated that: (a) mtDNA organization is different between mitochondrial genomes of fertile and sterile lines but identical in two different fertile tobacco lines; however genetic similarity among different mitochondrial genome types can be revealed by restriction fragment patterns; (b) although several differences were detected between the male-sterile and male-fertile plants, most of these were related to the origin of the mitochondria (cytoplasm donorNicotiana species); (c) identical mtDNA rearrangements — distinct to the cytoplasm donor — occur in cytoplasmic malesterile tobacco analogs bearing cytoplasm fromN. bigelovii in two differentN. tabacum nuclear backgrounds, indicating that mitochondrial genome structure inNicotiana is altered by substitution of the nuclear back-ground, since (d) inter- and intraspecific mitochondrial genome diversity among differentNicotiana species and the corresponding alloplasmic CMS tobacco analogs can be determined by hybridization with mtDNA specific probes. Analysis of in organello translation products in the three CMS-systems described confirmed the presence of variant proteins synthesized by mitochondria from CMS and male-fertileNicotiana isonuclear lines. In addition, differences due to the origin of both the nucleus and the cytoplasm, which involve changes in the presence or size of particular polypeptides, are apparent. A common feature of all three systems — including two different nuclear backgrounds — is the enhanced synthesis of a 31-kDa polypeptide in the strictly isonuclear CMS lines compared to the male-fertile tobacco. In addition, organellar gene expression was studied by Northern blot analysis of transcripts homologous to mitochondrial gene probes, revealing variant mtRNA species associated with some CMS lines.
    Materialart: Digitale Medien
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