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  • 2000-2004  (27)
  • 1990-1994  (12,615)
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  • transformation
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  • 1
    Electronic Resource
    Electronic Resource
    The Effects of Molybdenum on the High-Temperature Oxidation Resistance of Thin Foils of Fe–20Cr–5Al at Very High Temperatures (2000)
    Springer
    Oxidation of metals 53 (2000), S. 561-576 
    Details
    ISSN: 1573-4889
    Keywords: Fe–Cr–Al alloy ; oxidation ; molybdenum ; breakaway oxidation ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Thin foils of Fe–20Cr–5Al alloys are susceptible to breakawayoxidation once the aluminum content of the substrate has fallen below somecritical value. The combined addition of 0.1 wt.% lanthanum and 0, 1, or 2wt% molybdenum has a beneficial effect on the high-temperature oxidation ofsuch foils. Lanthanum has the well-known reactive-element effect on adhesionof the protective alumina scale, thereby increasing the time to onset ofbreakaway oxidation, while, for alloys containing molybdenum, breakawayoxide spreads relatively slowly over the specimen in comparison to alloysthat contain no molybdenum. In particular, molybdenum-containing alloys areable to develop a protective Cr2O3 layer at the breakawayoxide–substrate interface. Conversely, molybdenum-free alloys form aninternal-oxide zone in the substrate adjacent to this interface, rather thana Cr2O3 layer, so breakaway oxide spreads rapidly. A martensitic phase isobserved in the substrate adjacent to the breakaway oxide formed on Fe–20Cr–5Al–La specimens, which means that theα-phase has transferred to the γ -phase at the temperature ofthe oxidation test (1150°C). Conversely, α-phase is retained inthe molybdenum-containing alloy, even after breakaway takes place, sincemolybdenum, which is a strong ferrite former, is enriched in the alloyadjacent to areas of breakaway oxide. The diffusion rate of chromium isslower in the γ than in the α-phase so a continuouschromium-rich oxide layer, which is effective in inhibiting breakawayoxide from spreading, cannot be established at the breakawayoxide–substrate interface for the molybdenum-free alloys.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1004689211302
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  • 2
    Electronic Resource
    Electronic Resource
    Transformation of the tropane alkaloid-producing medicinal plant Hyoscyamus muticus by particle bombardment (2000)
    Springer
    Transgenic research 9 (2000), S. 163-168 
    Details
    ISSN: 1573-9368
    Keywords: Hyoscyamus muticus ; particle bombardment ; transformation ; tropane alkaloids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We report an efficient whole plant transformation system for Hyoscyamus muticus, an important medicinal plant of the Solanaceous family. We developed a system using a plasmid carrying the nptII and gusA genes, which was delivered into leaf explants by particle bombardment. Ten percent of bombarded leaf explants formed kanamycin-resistant callus, from which putative transgenic plants were recovered. The nptII gene conferring kanamycin resistance was found to be incorporated into the genome of all transgenic plants screened. Over 50% of the kanamycin resistant plants showed strong expression of the non-selected gusA gene. The majority of transgenic plants reached maturity, could be self pollinated, and produced fertile seed. A simple and efficient whole plant transformation system for this medicinal plant is an important step in furthering our understanding of tropane alkaloid production in plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008912330067
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  • 3
    Electronic Resource
    Electronic Resource
    Transgenic Trifolium repens with foliage accumulating the high sulphur protein, sunflower seed albumin (2000)
    Springer
    Transgenic research 9 (2000), S. 103-113 
    Details
    ISSN: 1573-9368
    Keywords: inheritance ; Rubisco small subunit promoters ; sonication ; sulphur nutrition ; sunflower albumin ; transformation ; white clover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract With the aim of increasing the rumen-protected level of the sulphur amino acids cysteine and methionine in Trifolium repens, we introduced the coding sequence of the sunflower seed albumin (SSA) into T. repens by Agrobacterium tumefaciens-mediated transformation. The SSA gene was modified such that the protein would be localised to the endoplasmic reticulum (ER). Four different T-DNA constructions all containing the SSA gene driven by either the promoter of a gene encoding the small subunit of ribulose bisphosphate carboxylase (Rubisco) from Arabidopsis thaliana (A ssu), the promoter of the gene encoding the small subunit of Rubisco of Medicago sativa (L ssu), or the Cauliflower Mosaic Virus 35S promoter (CaMV35S), were transferred to T. repens cv. Haifa. Transgenic T 0-plants and inter-transgenic hybrids were analysed for the level of SSA accumulation in the leaves by western blotting. The highest observed level of SSA accumulation was 0.1% of total extractable leaf protein. We observed that the promoter had a substantive effect on the level of SSA accumulation with A ssu〉CaMV35S〉L ssu. Results from the inter-transgenic hybrids showed that the capacity to synthesise SSA was inherited. However the level of SSA accumulation in the leaves generally appears not to be additive with extra transgenic loci. During this work, we attempted to improve the efficiency of A. tumefaciens-mediated transformation of T. repens using the SAAT-method (Sonication Assisted Agrobacterium-mediated Transformation) on cotyledons of T. repens. T-DNA transfer was in general not enhanced by sonication compared to traditional A. tumefaciens-mediated transformation. Furthermore, Southern blot analyses of plants regenerated from the same cotyledon after A. tumefaciens treatment and under selection, indicated that multiple shoots were usually derived from the same transformation event. We concluded from these results that only one plant from each A. tumefaciens-treated cotyledon should be taken to avoid transgenic clones.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008967409302
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  • 4
    Electronic Resource
    Electronic Resource
    Efficient Production of Transgenic Cassava Using Negative and Positive Selection (2000)
    Springer
    Transgenic research 9 (2000), S. 405-415 
    Details
    ISSN: 1573-9368
    Keywords: Manihot esculenta ; transformation ; Agrobacterium tumefaciens ; mannose ; hygromycin ; selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to improve the efficiency of cassava (Manihot esculenta Crantz) transformation, two different selection systems were assessed, a positive one based on the use of mannose as the selective agent, and a negative one based on hygromycin resistance encoded by an intron-containing hph gene. Transgenic plants selected on mannose or hygromycin were regenerated for the first time from embryogenic suspensions cocultivated with Agrobacterium. After the initial selection using mannose and hygromycin, 82.6% and 100% of the respective developing embryogenic callus lines were transgenic. A system allowing plant regeneration from only transgenic lines was designed by combining chemical selection with histochemical GUS assays. In total, 12 morphologically normal transgenic plant lines were produced, five using mannose and seven using hygromycin. The stable integration of the transgenes into the nuclear genome was verified using PCR and Southern analysis. RT-PCR and northern analyses confirmed the transgene expression in the regenerated plants. A rooting test on mannose containing medium was developed as an alternative to GUS assays in order to eliminate escapes from the positive selection system. Our results show that transgenic cassava plants can be obtained by using either antibiotic resistance genes that are not expressed in the micro-organisms or an antibiotic-free positive selection system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026509017142
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  • 5
    Electronic Resource
    Electronic Resource
    Floral Spray Transformation Can Efficiently Generate Arabidopsis (2000)
    Springer
    Transgenic research 9 (2000), S. 471-486 
    Details
    ISSN: 1573-9368
    Keywords: Arabidopsis thaliana ; Agrobacterium tumefaciens ; floral spray ; SOD ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this study, floral spray and floral dip were used to replace the vacuum step in the Agrobacterium-mediated transformation of a superoxide dismutase (SOD) gene into Arabidopsis. The transgene was constructed by using a CaMV 35S promoter to drive a rice cytosolic CuZnSOD coding sequence in Arabidopsis. The transgene construct was developed in binary vectors and mobilized into Agrobacterium. When Arabidopsis plants started to initiate flower buds, the primary inflorescence shoots were removed and then transformed by floral spray or floral dip. More than 300 transgenic plants were generated to assess the feasibility of floral spray used in the in planta transformation. The result indicates that the floral spray method of Agrobacterium can achieve rates of in planta transformation comparable to the vacuum-infiltration and floral dip methods. The floral spray method opens up the possibility of in planta transformation of plant species which are too large for dipping or vacuum infiltration.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026522104478
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  • 6
    Electronic Resource
    Electronic Resource
    Changes in lipid and protein constituents of rafts and caveolae in multidrug resistant cancer cells and their functional consequences (2000)
    Springer
    Glycoconjugate journal 17 (2000), S. 253-259 
    Details
    ISSN: 1573-4986
    Keywords: Cancer ; caveolae ; caveolin ; cholesterol ; glucosylceramide ; multidrug resistance ; rafts ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The carcinogenic process involves a complex series of genetic and biochemical changes that enables transformed cells to proliferate, migrate to secondary sites and, in some cases, acquire mechanisms that make cancer cells resistant to chemotherapy. This phenomenon in its most common form is known as multidrug resistance (MDR). It is usually mediated by overexpression of P-glycoprotein (P-gp) or other plasma membrane ATPases that export cytotoxic drugs used in chemotherapy, thereby reducing their efficacy. However, additional adaptive changes are likely to be required in order to confer a full MDR phenotype. Recent studies have shown that acquisition of MDR is accompanied by up-regulation of lipids and proteins that constitute lipid rafts and caveolar membranes, notably glucosylceramide and caveolin. These changes may be related to the fact that in MDR cells a significant fraction of cellular P-gp is associated with caveolin-rich membrane domains, they may be involved in drug transport and they could have an impact on drug-induced apoptosis and on the phenotypic transformation of MDR cancer cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026553626537
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  • 7
    Electronic Resource
    Electronic Resource
    Transformation of Brassica juncea (L.) Czern with bacterial codA gene enhances its tolerance to salt stress (2000)
    Springer
    Molecular breeding 6 (2000), S. 489-499 
    Details
    ISSN: 1572-9788
    Keywords: Choline oxidase ; glycinebetaine ; transformation ; Brassica juncea ; salt stress
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The codA gene for biosynthesis of glycinebetaine from Arthrobacter globiformis was used for transforming Brassica juncea cv. Pusa Jaikisan (which lack any means to synthesize glycinebetaine) through Agrobacterium mediated transformation. The stable insertion of the codA gene in the shoots obtained on medium with kanamycin and hygromycin was confirmed by PCR analysis of the nptII gene. Southern hybridization with a codA probe further demonstrated its successful integration. Immunoblot analysis revealed the presence of choline oxidase demonstrating that the bacterial codA gene had been successfully transcribed and translated. The seeds of transgenic lines showed enhanced capacity to germinate under salt stress as compared to that of the wild type. Further, the seedlings of transgenic plants that expressed codA gene showed significantly higher growth than that of the wild type under salt stress conditions. These results demonstrated that the introduction of a biosynthetic pathway for glycinebetaine into Brassica juncea significantly enhanced their salt tolerance. Hence, homozygous genotypes of selected transformed lines can be exploited for improving the salt tolerance of the desirable cultivars of Brassica juncea through breeding programmes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026542109965
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  • 8
    Electronic Resource
    Electronic Resource
    Field resistance to Tomato spotted wilt virus in transgenic peanut (Arachis hypogaea L.) expressing an antisense nucleocapsid gene sequence (2000)
    Springer
    Molecular breeding 6 (2000), S. 227-236 
    Details
    ISSN: 1572-9788
    Keywords: antisense DNA ; co-transformation ; nucleocapsid gene ; pathogen-derived resistance ; somatic embryogenesis ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Peanut (Arachis hypogaea L.) lines transgenic for the antisense nucleocapsid (N) gene of a Tomato spotted wilt virus (TSWV) strain isolated from peanut were generated by microprojectile-mediated transformation of repetitive somatic embryos of cultivars VC1 and AT120. The selectable marker (hygromycin resistance) and the N gene were on separate plasmids. A total of 207 VC1 and 120 AT120 hygromycin-resistant lines were produced. Of all the VC1 plants recovered 71% were cotransformed with the N gene (N+), but all plants were sterile. For AT120, 48 of the transgenic cell lines converted into plants. Polymerase chain reaction (PCR) screening showed 15 of the lines were transgenic for the N gene (N+), and two of these lines were fertile. A field test was conducted in 1998 at Ashburn, GA, using seeds from each fertile line, along with segregated and non-transgenic controls. Plants from four randomly selected field plots were examined for symptoms and analyzed by double-antibody sandwich enzyme-linked immunoabsorbent assay and PCR at 10 and 14 weeks after planting. At 14 weeks, 76% of the N+ plants were symptomless, while 2% were severely symptomatic or dead. In contrast, only 42% of the plants lacking the N gene were symptomless and 50% were severely symptomatic or dead. Northern blot analysis of selected field-resistant plants detected transgene RNA, and the transcript level appeared undiminished after viral exposure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009649408157
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  • 9
    Electronic Resource
    Electronic Resource
    Insect- and herbicide-resistant transgenic eucalypts* (2000)
    Springer
    Molecular breeding 6 (2000), S. 307-315 
    Details
    ISSN: 1572-9788
    Keywords: bar ; cry3A ; Eucalyptus ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Transgenic Eucalyptus camaldulensis containing both the insecticidal cry3A gene and the bar gene (conferring tolerance to the herbicide glufosinate ammonium) have been produced by Agrobacterium tumefaciens-mediated transformation of seedling explants. Transgenic plants from two lines tested were resistant to first instars of chrysomelid beetles that are important pests of commercial Australian eucalypt plantations. Both lines also exhibit tolerance to the broad-spectrum herbicide Liberty® at 6 l/ha (1.2 kg active ingredient per hectare), twice the field application rate. Transgenic insect- and herbicide-resistant eucalypts like these are likely to provide better insect and weed control options in plantations, particularly during the vulnerable establishment phase, provided that any adverse ecological impacts of releasing transgenic trees into the environment can be assessed and minimized.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009676214328
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  • 10
    Electronic Resource
    Electronic Resource
    Transformation of Japanese persimmon (Diospyros kaki Thunb.) with a bacterial gene for choline oxidase (2000)
    Springer
    Molecular breeding 6 (2000), S. 501-510 
    Details
    ISSN: 1572-9788
    Keywords: choline oxidase ; glycinebetaine ; Japanese persimmon ; salt tolerance ; transformation ; woody plant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This report describes the first successful genetic engineering of tolerance to salt in an agriculturally important species of woody plants by Agrobacterium-mediated transformation with the codA gene of Arthrobacter globiformis. This gene encodes choline oxidase, which catalyzes the oxidation of choline to glycinebetaine. The binary plasmid vector pGC95.091, containing a kanamycin-resistance gene (nptII), a gene for β-glucuronidase (gusA) and the codA gene in its T-DNA region, was used with a disarmed strain of Agrobacterium tumefaciens, EHA101, to transform Japanese persimmon (Diospyros kaki Thunb. `Jiro') by the leaf disk transformation method. The pRS95.101 plasmid that included only nptII and gusA in the T-DNA region was used as a control. We selected eight transgenic lines with one or two copies of the T-DNA after transformation with pGC95.091 (PC lines) and three lines after transformation with pRS95.101 (PR lines). The eight PC lines produced choline oxidase and glycinebetaine whereas neither was found in untransformed `Jiro' and in the control PR lines. Transgenic plants grew normally, resembling wild-type plants both in vitro and ex vitro. The activity of photosystem II in leaves of the transgenic Japanese persimmon plants under NaCl stress was determined in terms of the ratio of the variable (F v) to the maximum (F m) fluorescence of chlorophyll (F v/F m). The rate of decline in (F v/F m under NaCl stress was lower in the PC lines than in the control PR lines. These results demonstrated that genetic engineering of Japanese persimmon, which allowed it to accumulate glycinebetaine, enhanced the tolerance to salt stress of this plant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026513831290
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  • 11
    Electronic Resource
    Electronic Resource
    Study of the factors influencing Agrobacterium-mediated transformation of pea (Pisum sativum L.) (2000)
    Springer
    Molecular breeding 6 (2000), S. 185-194 
    Details
    ISSN: 1572-9788
    Keywords: Agrobacterium ; transformation ; pea ; Pisum sativum L. ; PCR analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Factors influencing the efficiency of Agrobacterium-mediated transformation of pea were tested using highly efficient, direct regeneration system. The virulence of three Agrobacterium strains (octopine LBA 4404, nopaline C58C1 and succinamopine, hypervirulent EHA 105) clearly varied giving 1 transgenic plant per 100 explants for LBA 4404, 2.2 for C58C1 and 8.2 for EHA 105. To test the efficacy of selection agents we used the hypervirulent EHA 105 strain carrying pGPTV binary vector with one of four different selection genes: nptII, hpt, dhfr or bar. The mean number of transgenic, kanamycin-resistant plants for two cultivars tested was 4.2 per 100 explants and was slightly higher than the number of phosphinothricin-resistant plants (3.6 plants per 100 explants). The proportion of transgenics among kanamycin-selected plants was also higher than among phosphinothricin-resistant plants (35% and 28% respectively). There was no regeneration on hygromycin or methotrexate media (transformation with hpt and dhfr genes). Acetosyringone had no apparent influence on efficiency of transformation with hypervirulent EHA 105 strain, however it did affect the rate of transformation when moderately virulent C58C1 was used. Recovery of transgenic plants was enhanced after application of 5-azacytidine. The presence of integrated T-DNA was checked by PCR and confirmed by Southern hybridization. T-DNA was stably transmitted to the next generation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009679908948
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  • 12
    Electronic Resource
    Electronic Resource
    Generation of transgenic wheat (Triticum aestivum L.) for constitutive accumulation of an Aspergillus phytase (2000)
    Springer
    Molecular breeding 6 (2000), S. 195-206 
    Details
    ISSN: 1572-9788
    Keywords: heterologous protein accumulation ; phytate phosphorus digestibility ; phytase ; phytic acid ; transformation ; Triticum aestivum L.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The Aspergillus niger phytase-encoding gene (phyA) has been constitutively expressed in wheat. Transgenic wheat lines were generated by microprojectile bombardment of immature embryos, using the bar-Bialaphos selection system. The bar and the phyA gene expression were controlled by the maize ubiquitin-1 promoter. To ensure secretion and glycosylation of the microbial phytase, an expression cassette was designed (Ubi-SP-Phy) where an α-amylase signal peptide sequence was inserted between the promoter and the phytase coding region. A similar cassette was constructed without the signal peptide sequence (Ubi-Phy). Five lines of fertile wheat transformed with the Ubi-SP-Phy were generated and two lines with the Ubi-Phy construct. The inheritance of the phyA gene was monitored through three generations. Western blotting of leaf and seed derived protein revealed the presence of an immunoreacting polypeptide of the size expected for the Aspergillus phytase. Up to 25 days after pollination, the heterologous phytase was exclusively present in the pericarp-seed coat-aleurone fraction. Thereafter, it accumulated in the endosperm in amounts exceeding that found in the seed coat and aleurone. The phyA mRNA and derived protein could at no stage be detected in the embryo. The Ubi-SP-Phy transgenic seeds exhibited up to 4-fold increase of phytase activity while up to 56% increase was found in Ubi-Phy plants. It is concluded that a functional Aspergillus phytase can be produced in significant amounts in wheat grains. This may be of relevance for improving the phytate-phosphorus digestibility when wheat grains are used for non-ruminant animal feed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009690730620
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  • 13
    Electronic Resource
    Electronic Resource
    Metamorphosis of a Non-Functioning Pituitary Adenoma to Cushing's Disease (2000)
    Springer
    Pituitary 3 (2000), S. 117-122 
    Details
    ISSN: 1573-7403
    Keywords: Cushing's disease ; silent ; pituitary ; tumour ; macroadenoma ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Silent pituitary adenomas occur in 25–40% of all clinically apparent pituitary tumours. However, the subsequent development of florid Cushing's disease in a patient with a previous non-functioning tumour is extremely rare. We describe a 47 year-old woman presenting initially with a large, invasive and recurrent, non-functioning pituitary tumour. Histopathologic study of the initial tissue did not stain for any hormones. Six years after the initial presentation, she manifested florid ACTH dependent Cushing's syndrome. A recurrent invasive pituitary macroadenoma necessitated a third transphenoidal surgery. The resected specimen, in this instance, revealed positive staining for ACTH, FSH, prolactin, and growth hormone on immunocytochemistry. An incomplete response to surgical, radiation and medical therapy necessitated a bilateral adrenalectomy to control the hypercortisolism, which resulted in remarkable clinical improvement. We also review five previous case reports from the revision literature of similar transformations from non-secreting pituitary adenomas to Cushing's disease. This subset of patients may represent yet another entity in the widening spectrum of Cushing's syndrome.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009961925780
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  • 14
    Electronic Resource
    Electronic Resource
    Transforming Self and Society: A "Critical Appreciation" Model (2000)
    Springer
    Systemic practice and action research 13 (2000), S. 475-501 
    Details
    ISSN: 1573-9295
    Keywords: reflection ; transformation ; self-society dynamics ; critical systems thinking ; systemic intervention ; critical self-reflection ; ideology-critique ; critical appreciation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Sociology
    Notes: Abstract This paper sets out to uncover some relationships between reflection, discourse and action. By challenging and synthesizing some polemical arguments concerning the creation, maintenance, and transformation of self and society, a model of self-society dynamics that operates through reflection, discourse, and action is developed. The model of self-society dynamics brings together aspects of self-reflection and ideology-critique (explored in the paper), which it is suggested are required for any intervention (transformative action) to be grounded in locally meaningful ways. By creating a dialog community in which self- and group assumptions can be subjected to validation through discourse, it is proposed that a dynamic balance between individual needs and broader societal aims may be achieved. If individuals can be open to such discourse (i.e., they can become critically self-reflective), then it is argued that possibilities for achieving sustainable change will be significantly enhanced.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009541430809
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  • 15
    Electronic Resource
    Electronic Resource
    Factors involved in Agrobacterium tumefaciens-mediated gene transfer into Pinus nigra Arn. ssp. salzmannii (Dunal) Franco (2000)
    Springer
    Euphytica 114 (2000), S. 195-203 
    Details
    ISSN: 1573-5060
    Keywords: conifers ; salgareño pine ; tissue culture ; transformation ; transient gene expression ; uidA expression ; vir gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Cotyledons from dissected sterile embryos of salgareño pine (Pinus nigra Arn. ssp. salzmannii (Dunal) Franco) were inoculated with different disarmed Agrobacterium tumefaciens strains harbouring the binary vector p35SGUSint. The transient expression of a β-glucuronidase gene (uidA) was studied, using a histochemical staining procedure. Nineteen days after inoculation, the activity of β-glucuronidase was detected in epidermal and subepidermal layers of cotyledonary explants. The EHA105 strain harbouring a disarmed agropine-type Ti-plasmid (pTiBO542) was the most effective for gene transfer of the uidA gene. The effects of exudates and extracts from 0-day-old embryos on induction of vir gene expression in A. tumefaciens were also examined. The results of this study showed that salgarño pine embryo exudates contain a substance(s) that induce vir gene expression, in similar way to that observed with 100 μM acetosyringone (AS).All these findings suggest that T-DNA processing and transfer might take place when Agrobacterium infects suitable tissues of salgareño pine.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003946131356
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  • 16
    Electronic Resource
    Electronic Resource
    Towards genetic transformation in the monocot Alstroemeria L. (2000)
    Springer
    Euphytica 115 (2000), S. 17-26 
    Details
    ISSN: 1573-5060
    Keywords: cell suspension ; monocotyledon ; selection ; somatic embryogenesis ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The successful application of plant biotechnology to Alstroemeria improvement will largely depend on the availability of an efficient regeneration/transformation system. Regeneration in Alstroemeria is accomplished from nodular embryogenic callus initiated from zygotic embryos. Histological studies of embryogenic callus initiation from 4-weeks old cultured ovules revealed that the outermost layers of the protoderm of the embryogenic nodules divided to form either a new nodule or aproembryo. Transient gene expression after particle bombardment of nodular embryogenic callus was optimized using DNA of pAHC25. The highest β-glucuronidase expression was found when the GUS gene was under control of the maize ubiquitin promoter, the target tissue was placed 5 cm below the microcarrier launch assembly and when the rupture disc-breakage point was between 650–900 psi. Kanamycin blocked regeneration of somatic embryos, however, did not block growth of nodular embryogenic callus. With phosphinothricin both callus growth and regeneration were blocked. Bombardment of nodular embryogenic callus with DNA of pAHC25 combined with selection on medium containing phosphinothricin resulted in putative transgenic chimeric. Friable calli were selected from nodular embryogenic callus and used to initiate suspensions. These cell suspensions were subjected to transformation by particle bombardment using DNA of pAHC25 and resulted in a stable transformed friable callus line after selection based on luciferase activity. Even after 2 years of maintenance this callus line was luciferase positive and the Polymerase Chain Reaction analysis demonstrated the presence of the introduced gene in this friable callus line.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003979423469
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  • 17
    Electronic Resource
    Electronic Resource
    Rapid transformation and regeneration of alfalfa (Medicago falcata L.) via direct somatic embryogenesis (2000)
    Springer
    Plant growth regulation 31 (2000), S. 155-166 
    Details
    ISSN: 1573-5087
    Keywords: alfalfa ; cell division cycle ; somatic embryogenesis ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Two simple, rapid and efficient protocols for theregeneration of transformed tetraploid lines ofalfalfa (Medicago falcata L.) have beendeveloped and compared. Leaf explants fromembryogenic lines 47/1-150 and 47/1-5 were inoculatedwith Agrobacterium tumefaciens containingconstructs carrying the nptII selectable markergene and promoter:gusA gene fusions under thecontrol of the CaMV 35S or Arabidopsis cdc2a,CycB1 and CycA2 promoters. In the firstregeneration system (the MSH system), inoculated leafexplants were incubated on MS medium supplemented with2,4-D and kinetin and then subcultured onto plantgrowth regulator-free MS medium in order to inducedirect somatic embryogenesis. In the secondregeneration system (the B5h system), the inoculatedexplants were incubated on B5h medium to induceindirect production of somatic embryos viaembryogenic callus. In both systems, an effectivekanamycin selection regime was employed and wasmaintained when the embryos were subcultured onto arecovery medium (Boi2Y) to promote further embryodevelopment. The use of Boi2Y medium was particularlyimportant for shortening the regeneration time andpromoting a higher frequency of healthy plantletproduction from the somatic embryos. The maturesomatic embryos were finally transferred to plantgrowth regulator-free MS medium for plantletformation. Transgenic plantlets were produced within10–14 weeks in the MSH system and 12–16 weeks in theB5h system. The MSH system appears to be the fastesttransformation system reported for leguminous speciesto date. Confirmation of transformation was obtainedusing a re-callusing assay on kanamycin and subsequentSouthern blot hybridisation and PCR analysis. Theability to induce expression of GUS activity in leafexplants containing the cell division cycle genepromoter:gusA constructs by 2,4-D treatment alsoproved to be a reliable indicator of transformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006306909722
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  • 18
    Electronic Resource
    Electronic Resource
    Agrobacterium-mediated sorghum transformation (2000)
    Springer
    Plant molecular biology 44 (2000), S. 789-798 
    Details
    ISSN: 1573-5028
    Keywords: Agrobacterium tumefaciens ; sorghum ; transformation ; transgenic plants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Agrobacterium tumefaciens was used to genetically transform sorghum. Immature embryos of a public (P898012) and a commercial line (PHI391) of sorghum were used as the target explants. The Agrobacterium strain used was LBA4404 carrying a `Super-binary' vector with a bar gene as a selectable marker for herbicide resistance in the plant cells. A series of parameter tests was used to establish a baseline for conditions to be used in stable transformation experiments. A number of different transformation conditions were tested and a total of 131 stably transformed events were produced from 6175 embryos in these two sorghum lines. Statistical analysis showed that the source of the embryos had a very significant impact on transformation efficiency, with field-grown embryos producing a higher transformation frequency than greenhouse-grown embryos. Southern blot analysis of DNA from leaf tissues of T0 plants confirmed the integration of the T-DNA into the sorghum genome. Mendelian segregation in the T1 generation was confirmed by herbicide resistance screening. This is the first report of successful use of Agrobacterium for production of stably transformed sorghum plants. The Agrobacterium method we used yields a higher frequency of stable transformation that other methods reported previously.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026507517182
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  • 19
    Electronic Resource
    Electronic Resource
    A computational procedure for joining separate map sheets (2000)
    Springer
    GeoJournal 52 (2000), S. 253-262 
    Details
    ISSN: 1572-9893
    Keywords: map sheets ; GIS ; seamless spatial database ; transformation ; computational procedure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract Map sheets have been often used as a basic spatial unit for managing spatial data produced from paper maps. This often results in incompatibility between adjacent map sheets, because spatial objects do not cross the boundaries smoothly and even the boundaries themselves do not match their neighbors exactly. To solve the problem this paper proposes a computational procedure for joining separate map sheets to obtain seamless spatial data. Line objects digitized separately in different map sheets are considered, which are frequently used to represent road networks, gas pipelines, and boundaries of polygon objects. The procedure consists of three steps: (1) extraction of end nodes, (2) detection of matching nodes, and (3) transformation of the map sheet. Each step goes interactively so that unexpected errors can be avoided by human observation. To test the validity of the procedure, map sheets are combined containing the road network data of Tokyo 23-ku area, Japan.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1014224325346
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  • 20
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    Electronic Resource
    The changing geography of morbidity and mortality in post-communist Poland (2000)
    Springer
    GeoJournal 50 (2000), S. 97-100 
    Details
    ISSN: 1572-9893
    Keywords: disease ; health ; morbidity ; mortality ; pollution ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract In general, the health of Poles improved markedly in the thirty years after the Second World War, but there was some deterioration after 1989 before improvement resumed. Only in the case of cancer is there an upward trend and so Poles are now healthier than they have been at any time in the past. However there are sharp regional variations well exemplified by the incidence of tuberculosis, where there appears to be some correlation with poorer housing and atmospheric pollution. High death rates in Lodz (consistently the highest in the country at the voivodship level between 1989 and 1996), may also be linked with environmental pollution as well as the ageing of the population. Variations between town and country are small, but Poland shows up in a poor light when compared with other European countries. These are important issues for the administration and financing of the welfare services.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007127431508
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  • 21
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    Electronic Resource
    Socioeconomic transformation in rural Romania through the eyes of experts: Demographic and social issues (2000)
    Springer
    GeoJournal 50 (2000), S. 151-155 
    Details
    ISSN: 1572-9893
    Keywords: demography ; experts ; rural ; Romania ; rural development ; social issues ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geography
    Notes: Abstract There is no standard model of transformation for post- socialist countries and each country encounters specific problems rooted in the geographical characteristics of the areas concerned. The human resources are of the greatest importance because it really matters how people (especially the decision-makers) perceive system change and continually reformulate their expectations and strategies; so investigations into the views of people caught up in the transformation can provide a deeper understanding of the background to structural change. Working the national, regional level and local levels in Romania, experts were asked to consider the advantages and disadvantages arising out of the transformation, the most important problems and constraints for future rural development and the policies needed. The paper examines the responses on demographic and social issues. It emerges the most detailed responses were supplied by local-level representatives while respondents at the regional level steered a middle course between the need to address local problems and the prime importance of stimulating the Romanian economy so as to generate resources for welfare programmes (with the latter issue the overriding concern of interviewees at national level). There was general agreement on the importance of foreign investment and European integration for economic development, with local actors taking only small steps in line with the existing opportunities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007120608735
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  • 22
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    Electronic Resource
    The effect of DNA/gold particle preparation technique, and particle bombardment device, on the transformation of barley (Hordeum vulgare) (2000)
    Springer
    Euphytica 111 (2000), S. 67-76 
    Details
    ISSN: 1573-5060
    Keywords: Barley ; Hordeum vulgare ; transformation ; particle bombardment ; particle gun
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Immature embryos of the spring barley variety GoldenPromise, were bombarded with three different particledelivery systems and both transient and stabletransformation examined. In addition, a range oftechniques for the preparation of the DNA coated goldparticles was examined. Fertile transgenic barleyplants were obtained using three particle preparationtechniques which differed in the amount of gold andDNA used for each bombardment. However, only one ofthe particle delivery systems, the PDS 1000/He device,appeared to be effective in yielding transformedbarley plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003700300235
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  • 23
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    Electronic Resource
    Enhanced forskolin production in genetically transformed cultures of Coleus forskohlii by casein hydrolysate and studies on growth and organisation (2000)
    Springer
    Biotechnology letters 22 (2000), S. 133-136 
    Details
    ISSN: 1573-6776
    Keywords: casein hydrolysate ; Coleus forskohlii ; forskolin ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Casein hydrolysate at 2.0 g l−1 significantly enhanced forskolin content (2.3 mg g−1 cell dry wt) in a rhizogenic tumourous line, GCO-RCH-2 of Coleus forskohlii. In rooty teratoma line, RC-ST-2/4, forskolin content enhanced to 1.7 mg g−1 cell dry wt in presence of 2.5 g l−1 casein hydrolysate. Unlike untransformed calli and rhizogenic/root cultures, all the forskolin yielding transformed cultures of C. forskohlii have been maintained for over 5 years.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005618307074
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  • 24
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    Electronic Resource
    Two types of new algorithms for finding explicit analytical solutions of nonlinear differential equations (2000)
    Springer
    Applied mathematics and mechanics 21 (2000), S. 1423-1431 
    Details
    ISSN: 1573-2754
    Keywords: nonlinear differential equations ; transformation ; algorithm ; analytical solution ; O175.29
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Mathematics , Physics
    Notes: Abstract The idea of AC=BD was applied to solve the nonlinear differential equations. Suppose that Au=0 is a given equation to be solved and Dv=0 is an equation to be easily solved. If the transformation u=Cv is obtained so that v satisfies Dv=0, then the solutions for Au=0 can be found. In order to illustrate this approach, several examples about the transformation C are given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02459221
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  • 25
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    Electronic Resource
    Metal resistance in Pseudomonas strains isolated from soil treated with industrial wastewater (2000)
    Springer
    World journal of microbiology and biotechnology 16 (2000), S. 177-182 
    Details
    ISSN: 1573-0972
    Keywords: Conjugation ; metal resistance ; plasmid DNA ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Heavy metal concentrations in soil treated with industrial wastewater of Aligarh City (U.P.), India were determined. The analysis of test samples revealed high levels of Fe, Zn, Ni and Cu. A total of 45 Pseudomonas spp. were isolated from soil and were characterized on the basis of morphological, cultural and biochemical characteristics. MICs of Hg2+, Cd2+, Cu2+, Cr3+, and Zn2+ for each isolate were determined. Eighty percent of the strains isolated from soil harboured resistance to copper, whereas 73.3% of the isolates exhibited resistance to cadmium, 71.1% to chromium and zinc and 48.8% to mercury. A maximum MIC of 200 μg/ml for mercury and 1600 μg/ml for other metals was observed. Metal resistance was found to be plasmid mediated as evidenced by transformation studies. Further, the transmissible nature of chromium resistance was confirmed by conjugation. Agarose gel electrophoresis using the miniprep method for plasmid isolation revealed that these isolates harboured plasmids of molecular weights (45 & 47 kb) using EcoRI and HindIII digests of λDNA and undigested λDNA as standard markers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008905902282
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  • 26
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    Electronic Resource
    Bringing “The Dead” to Life: Reading James Joyce (2000)
    Springer
    Journal of applied psychoanalytic studies 2 (2000), S. 109-115 
    Details
    ISSN: 1573-3459
    Keywords: James Joyce ; “The Dead” ; fiction ; reading ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Psychology
    Notes: Abstract The author offers a personal reading of James Joyce's “The Dead.” She focuses on how the sounds of the language are used to portray the main character's deadness and his beginning to come to life once the barriers to inner self and self-knowledge are broken.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010193724350
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  • 27
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    Electronic Resource
    Transformation of batridene (2000)
    Springer
    Chemistry of natural compounds 36 (2000), S. 137-139 
    Details
    ISSN: 1573-8388
    Keywords: 1,1′,6,6′,7,7′-hexahydroxy-3,3′-dimethyl-5,5′-diisopropyl-2,2′-dinaphthylidene-8,8′-dibarbituric acid ; transformation ; DMSO
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Transformations of 1,1′,6,6′,7,7′-hexahydroxy-3,3′-dimethyl-5,5′-diisopropyl-2,2′-dinaphthylidene-8,8′-dibarbituric acid (batridene) in DMSO are studied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02236415
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  • 28
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    Electronic Resource
    Plasmid mediated silver resistance in Acinetobacter baumannii (1994)
    Springer
    BioMetals 7 (1994), S. 49-56 
    Details
    ISSN: 1572-8773
    Keywords: Acinetobacter ; conjugation ; curing ; plasmid ; silver uptake ; silver resistance ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Acinetobacter baumannii BL88, an environmental isolate, was resistant to 13 metals and 10 antibiotics. Plumbagin cured resistance to silver, cadmium, antimony, streptomycin and ampicillin at varying frequencies. However, only silver resistance transferred (1 × 10−6 recepient−1) to Escherichia coli K12 during conjugation. Correspondingly there was transfer of a 54 kb plasmid (pUPI199) from A. baumannii BL88. The plasmid transformed E. coli DH5α cells at a frequency of 1 × 10−8 recepient−1. The growth rate of E. coli DH5; (pUPI199) was slower as compared with E. coli DH5α. Plasmid pUPI199 was 76 and 9.6% stable in the host A. baumannii BL88 in the presence and absence of selection pressure, respectively. A. baumannii BL88 was found to accumulate and retain silver whereas E. coli DH5α (pUPI199) effluxed 63% of the accumulated silver ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00205194
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  • 29
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    Electronic Resource
    Canonical correlation and reduction of multiple time series (1994)
    Springer
    Annals of the Institute of Statistical Mathematics 46 (1994), S. 625-631 
    Details
    ISSN: 1572-9052
    Keywords: Rank of multiple time series ; transformation ; spectrum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract It is shown that a degenerate rankd-variate stationary time series can be reduced to a full rank time series of lower dimension via an orthogonal transformationT provided that ρ, the canonical correlation between past and future of the time series is strictly less than one. Procedures for estimation of rank of the multiple time series,T and testing ρ=1 are outlined, the latter is related to testing the unit root hypothesis in ARMA models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00773471
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  • 30
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    Electronic Resource
    Genetic ecology: A new interdisciplinary science, fundamental for evolution, biodiversity and biosafety evaluations (1994)
    Springer
    Cellular and molecular life sciences 50 (1994), S. 429-437 
    Details
    ISSN: 1420-9071
    Keywords: Genetics ; ecology ; DNA-transfer ; conjugation ; transformation ; transduction ; transposons ; dormant cells ; epilithon ; microbial colonisation ; symbiosis ; virus resistance ; biosafety ; release of genes ; insults to humanity ; evolution ; biodiversity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Genetic ecology is the extension of our modern knowledge in molecular genetics to studies of viability, gene expression and gene movements in natural environments like soils, aquifers and digestive tracts. In such milieux, the horizontal transfer of plasmid-borne genes between phylogenetically distant species has already been found to be much more frequent than had been expected from laboratory experience. For the study of exchanges involving chromosomally-located genes, more has to be learned about the behaviour of transposons in such environments. The results expected from studies in genetic ecology are relevant for considerations of evolution, biodiversity and biosafety. The role of this new field of research in restoring popular confidence in science and in its biotechnological applications is stressed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01920741
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  • 31
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    Agrobacterium-mediated transformation of white mustard (Sinapis alba L.) and regeneration of transgenic plants (1994)
    Springer
    Plant cell reports 13 (1994), S. 130-134 
    Details
    ISSN: 1432-203X
    Keywords: Sinapis alba L. ; Agrobacterium tumefaciens ; transformation ; regeneration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A procedure for the regeneration of fertile transgenic white mustard (Sinapis alba L.) is presented. The protocol is based on infection of stem explants of 7–9 day old plants with an Agrobacterium tumefaciens strain harboring a disarmed binary vector with chimeric genes encoding neomycin phosphotransferase and β-glucuronidase. Shoots are regenerated from callus-forming explants within 3–4 weeks. Under selection, 10% of the explants with transgenic embryonic callus develop into fertile transgenic plants. Rooting shoots transferred to soil yield seeds within 14–16 weeks following transformation. Integration and expression of the T-DNA encoded marker genes was confirmed by histochemical β glucuronidase assays and Southern-DNA hybridization using primary transformants and S1-progeny. The analysis showed stable integration and Mendelian inheritance of trans-genes in transformed Sinapis lines.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239878
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  • 32
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    Electronic Resource
    Stable expression of the GUS reporter gene in chrysanthemum depends on binary plasmid T-DNA (1994)
    Springer
    Plant cell reports 14 (1994), S. 59-64 
    Details
    ISSN: 1432-203X
    Keywords: Agrobacterium ; transformation ; T-DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three chrysanthemum (Dendranthema grandiflora) cultivars were cocultivated with 2 Agrobacterium tumefaciens strains in combination with 4 pBIN19 derived binary plasmids, all carrying the Nosnptll selection gene and 35Sgus(intron) reporter gene. All binary plasmids transferred DNA to chrysanthemum explants but only pMOG410 gave good stable expression of GUS. This plasmid differs from the other plasmids in 2 aspects: 1) It carries a restored nptll gene and 2) the selection gene is positioned at the left border side of the reporter gene. Cocultivation with AGLO(pMOG410) yielded up to 13 GUS positive shoots per 100 explants. The presence of the gus and nptll gene in recovered shoots was confirmed by PCR and Southern blot analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233300
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  • 33
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    Electronic Resource
    Isolation and transformation of rice aleurone protoplasts (1994)
    Springer
    Plant cell reports 13 (1994), S. 394-396 
    Details
    ISSN: 1432-203X
    Keywords: Rice ; α-amylase ; protoplasts ; aleurone ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Protoplasts isolated from the aleurone have been used extensively in molecular studies focusing on hormone-mediated regulation of gene expression in barley seed. To extend the use of aleurone protoplasts to other species, we have determined the conditions necessary for the isolation of protoplasts from rice aleurone layers of germinated seed. Many of the common cell wall degrading enzymes used in making protoplasts were tested for their ability to release protoplasts from rice aleurone layers. Cellulysin was found to be the most effective. Transformation of these aleurone protoplasts was accomplished using polyethylene glycol and DNA constructs containing the firefly luciferase reporter gene under the control of two different promoters were tested. Luciferase expression was 24-fold greater when the reporter gene was under the control of the CaMV 35S promoter than when the promoter from the alcohol dehydrogenase 1 gene was used. With the isolation and transformation of aleurone protoplasts from rice, it is now possible to investigate molecular events occurring in this tissue during germination.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00234145
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  • 34
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    Electronic Resource
    Molecular improvement of cereals (1994)
    Springer
    Plant molecular biology 25 (1994), S. 925-937 
    Details
    ISSN: 1573-5028
    Keywords: cereals ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00014667
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  • 35
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    Electronic Resource
    Identification of conserved domains in the Δ12 desaturases of cyanobacteria (1994)
    Springer
    Plant molecular biology 24 (1994), S. 643-650 
    Details
    ISSN: 1573-5028
    Keywords: Anabaena variabilis ; fatty-acid desaturation ; Synechococcus PCC7002 ; Synechococcus PCC7942 ; Synechocystis PCC6714 ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cyanobacterial genes for enzymes that desaturate fatty acids at the Δ12 position, designated desA, were isolated from Synechocystis PCC6714, Synechococcus PCC7002 and Anabaena variabilis by crosshybridization with a DNA probe derived from the desA gene of Synechocystis PCC6803. The genes of Synechocystis PCC6714, Synechococcus PCC7002 and A. variabilis encode proteins of 349, 347 and 350 amino acid residues, respectively. The transformation of Synechococcus PCC7942 with the desA genes from Synechocystis PCC6714, Synechococcus PCC7002 and A. variabilis was associated with the ability to introduce a second double bond at the Δ12 position of fatty acids. The amino acid sequence of the products of the desA genes revealed the presence of four conserved domains. Since one of the conserved domains was also found in the amino acid sequences of ω3 desaturases of Brassica napus and mung bean, this domain may play an essential role in the introduction of a double bond into fatty acids bound to membrane lipids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00023560
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  • 36
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    Electronic Resource
    Directed disruption of the Chlamydomonas chloroplast psbK gene destabilizes the photosystem II reaction center complex (1994)
    Springer
    Plant molecular biology 24 (1994), S. 779-788 
    Details
    ISSN: 1573-5028
    Keywords: Chlamydomonas reinhardtii ; chloroplast ; transformation ; photosystem II ; psbK
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using particle gun-mediated chloroplast transformation we have disrupted the psbK gene of Chlamydomonas reihardtii with an aadA expression cassette that confers resistance to spectinomycin. The transformants are unable to grow photoautotrophically, but they grow normally in acetate-containing medium. They are deficient in photosystem II activity as measured by fluorescence transients and O2 evolution and they accumulate less than 10% of wild-type levels of photosystem II as measured by immunochemical means. Pulse-labeling experiments indicate that the photosystem II complex is synthesized normally in the transformants. These results differ from those obtained previously with similar cyanobacterial psbK mutants that were still capable of photoautotrophic growth (Ikeuchi et al., J. Biol. Chem. 266 (1991) 1111–1115). In C. reinhardtii the psbK product is required for the stable assembly and/or stability of the photosystem II complex and essential for photoautotrophic growth. The data also suggest that the stability requirements of the photosynthetic complexes differ considerably between C. reinhardtii and cyanobacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00029859
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  • 37
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    Stable transformation and long-term expression of the gusA reporter gene in callus lines of perennial ryegrass (Lolium perenne L.) (1994)
    Springer
    Plant molecular biology 24 (1994), S. 401-405 
    Details
    ISSN: 1573-5028
    Keywords: Lolium perenne L. ; transformation ; rice gene GOS2 ; long-term GUS expression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Stable transformation of perennial ryegrass (Lolium perenne L.) was achieved by biolistic bombardment of a non embryogenic cell suspension culture, using the hpt and gusA gene. The transformation yielded on the average 5 callus lines per bombardment (1.4×106 cells). Stable integration of the genes into the plant genome was demonstrated by Southern analysis of DNA, isolated from hygromycin-resistant callus lines. The gusA reporter gene, which was regulated by the constitutive promoter of the rice gene GOS2, was expressed in both transient and stable transformation assays, indicating that this promoter is suitable for expression of a transferred gene in perennial ryegrass. Long-term GUS expression was observed in ca. 40% of the callus lines, whereas the other callus lines showed instability after 6 months and 1 year of culture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00020178
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  • 38
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    Structure and function of selectable and non-selectable transgenes in maize after introduction by particle bombardment (1994)
    Springer
    Plant molecular biology 25 (1994), S. 951-961 
    Details
    ISSN: 1573-5028
    Keywords: Cell biology ; epigenetics ; maize ; transformation ; transgenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Zea mays transformants produced by particle bombardment of embryogenic suspension culture cells of the genotype A188 × B73 and selected on kanamycin or bialaphos were characterized with respect to transgene integration, expression, and inheritance. Selection on bialaphos, mediated by thebar orpat genes, was more efficient than selection on kanamycin, mediated by thenptII gene. Most transformants contained multicopy, single locus, transgene insertion events. A transgene expression cassette was more likely to be rearranged if expression of that gene was not selected for during callus growth. Not all plants regenerated from calli representing single transformation events expressed the transgenes, and a non-selectable gene (uidA) was expressed in fewer plants than was the selectable transgene. Mendelian inheritance of transgenes consistent with transgene insertion at a single locus was observed for approximately two thirds of the transformants assessed. Transgene expression was typically, but not always, predictable in progeny plants-transgene silencing, as well as poor transgene transmission to progeny, was observed in some plant lines in which the parent plants had expressed the transgene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00014669
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  • 39
    Electronic Resource
    Electronic Resource
    Cloning of ω3 desaturase from cyanobacteria and its use in altering the degree of membrane-lipid unsaturation (1994)
    Springer
    Plant molecular biology 26 (1994), S. 249-263 
    Details
    ISSN: 1573-5028
    Keywords: desB gene ; desaturase ; fatty acid ; Synechococcus sp. PCC 7942 ; Synechocystis sp. PCC 6803 ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cyanobacteria respond to a decrease in temperature by desaturating fatty acids of membrane lipids to compensate for the decrease in membrane fluidity. Among various desaturation reactions in cyanobacteria, the desaturation of the ω3 position of fatty acids is the most sensitive to the change in temperature. In the present study, we isolated a gene, designated desB, for the ω3 desaturase from the cyanobacterium, Synechocystis sp. PCC 6803. The desB gene encodes a protein a 359 amino-acid residues with molecular mass of 41.9 kDa. The desB gene is transcribed as a monocistronic operon that produced a single transcript of 1.4 kb. The level of the desB transcript in cells grown at 22°C was 10 times higher than that in cells grown at 34°C. In order to manipulate the fatty-acid unsaturation of membrane lipids, the desB gene in Synechocystis sp. PCC 6803 was mutated by insertion of a kanamycin-resistance gene cartridge. The resultant mutant was unable to desaturate fatty acids at the ω3 position. The desA gene, which encodes the Δ12 desaturase of Synechocystis sp. PCC 6803, and the desB gene were introduced into Synechococcus sp. PCC 7942. Whilst the parent cyanobacterium can only desaturate membrane lipids at the Δ9 position of fatty acids, the resultant transformant was able to desaturate fatty acids of membrane lipids at the Δ9, Δ12 and ω3 positions. These results confirm the function of the desB gene and demonstrate that it is possible to genetically manipulate the fatty-acid unsaturation of membrane lipids in cyanobacteria.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00039536
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  • 40
    Electronic Resource
    Electronic Resource
    Cotton (Gossypium hirsutum L.) pollen-specific polygalacturonase mRNA: tissue and temporal specificity of its promoter in transgenic tobacco (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1989-1993 
    Details
    ISSN: 1573-5028
    Keywords: polygalacturonase ; pollen-specific promoter ; cotton ; transgenics ; transformation ; β-glucuronidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A gene (G9) expressed during late microsporogenesis in cotton (Gossypium hirsutum L.) was isolated. Sequence analysis of the cDNA (1.3 kb) as well as the gene (2.6 kb) revealed an open reading frame of 1233 bases encoding a protein of 43.9 kDa. The coding region of the gene is interrupted by three introns. Northern analysis of the RNA from developing anthers showed that the transcripts appear 12 days before anthesis and that the maximal concentration of RNA occurs in pollen on the day of anthesis. This pattern of gene expression suggests functions in post-anthesis events. Sequence comparisons with other known plant genes indicated that G9 is homologous to polygalacturonases. The G9 promoter conferred tissue and temporal specificity of β-glucuronidase (GUS) expression in transgenic tobacco plants. Thus, the G9 promoter can be used to drive gene expression in homologous as well as heterologous plants in a tissue-specific manner.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00019509
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  • 41
    Electronic Resource
    Electronic Resource
    Production of fertile transgenic maize by electroporation of suspension culture cells (1994)
    Springer
    Plant molecular biology 24 (1994), S. 51-61 
    Details
    ISSN: 1573-5028
    Keywords: Zea mays L. ; transformation ; electroporation ; bar ; phosphinothricin acetyltransferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Fertile, transgenic maize plants were generated by electroporation of suspension culture cells that were treated with a pectin-degrading enzyme. Electroporation of cells from two different suspension cultures, one derived from A188 X B73 and one derived from a B73-related inbred, with a plasmid containing the bar gene, resulted in high-frequency recovery of stably transformed callus lines. Plants were regenerated from thirteen transformed callus lines and transmission of bar to progeny was demonstrated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00040573
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  • 42
    Electronic Resource
    Electronic Resource
    Hairy roots of Brassica napus: II. Glutamine synthetase overexpression alters ammonia assimilation and the response to phosphinothricin (1994)
    Springer
    Plant cell reports 14 (1994), S. 41-46 
    Details
    ISSN: 1432-203X
    Keywords: Agrobacterium rhizogenes ; Brassica napus ; glutamine synthetase ; phosphinothricin ; rape ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Hairy roots of Brassica napus (rape cv. Giant) have been produced that contain the cytosolic glutamine synthetase (GS) gene from Glycine max (soybean). Leaf explants were cocultivated with Agrobacterium rhizogenes strain A4T harbouring the binary vector pLN16. This vector was constructed by inserting a soybean cytosolic GS cDNA into the multiple cloning site of pGA643, placing it under the control of the CaMV promoter. In addition, the T-DNA region of pLN16 contained a NPTII gene for selection of transformed cells. Transgenic hairy roots grew prolifically on hormone-free media containing a selective level of kanamycin. Southern and northern analyses confirmed the presence of soybean GS DNA and transcripts, respectively. These transformed hairy roots also have a greater abundance of the GS polypeptide, approximately 3–6 fold greater GS activity and lower levels of endogenous ammonia. Hairy roots provide a useful system for studying responses to phosphinothricin (PPT). Hairy roots grown in media containing PPT had lower GS activity, greater ammonia accumulation and slower growth than controls. The presence of the soybean GS gene in the hairy roots reduced these PPT-induced effects and resulted in higher GS activity, lower ammonia levels and faster growth than in PPT-treated controls. Greater tolerance of PPT was also seen in shoots regenerated from the hairy roots displaying elevated levels of GS activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233296
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  • 43
    Electronic Resource
    Electronic Resource
    T-DNA-insert-independent mutations induced in transformed plant cells duringAgrobacterium co-cultivation (1994)
    Springer
    Transgenic research 3 (1994), S. 317-325 
    Details
    ISSN: 1573-9368
    Keywords: Agrobacterium ; mutagenesis ; Nicotiana plumbaginifolia ; nitrate reductase ; ploidy ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transformation frequencies were determined for 1n, 2n, and 4n Nicotiana plumbaginifolia protoplast cultures inAgrobacterium-mediated gene transfer experiments. An unexpected large drop (50%) in plating efficiencies was observed in the non-selected (control) 1n populations after transformation treatment with virulent strains. This effect was not observed in the 2n or 4n cultures or in the 1n cultures when treated with avirulent bacteria. The mortality was disproportionally high and could not be explained by the low (0.1–0.5%) transformation efficiency in the 1n population, indicating mutagenesis of the cell populations independently from the T-DNA insertions. Mutagenesis was also indicated in gene tagging experiments where nitrate reductase-deficient (NR−) mutants were selected from haploidNicotiana plumbaginifolia protoplasts, as well as from leaf disc cultures or protoplasts of diploid plants that were heterozygotic for a mutation either in the NR apoenzyme gene (nia/wt) or one of the molybdenum-containing cofactor genes (cnxA/wt), afterAgrobacterium co-cultivation. The chlorate-resistant isolates were tested for the T-DNA-specific kanamycin resistance trait only after NR-deficiency had been established. Thirty-nine independent NR-deficient mutants were analysed further by Southern blot hybridization. There was no indication of integrated T-DNA sequences in the mutated NR genes, despite the fact that NR-deficient cells were found more frequently in cell populations which became transformed during the treatment than in the populations which did not. These observations suggest that transformation-competent cells undergo mutagenesis during theAgrobacterium gene transfer process not only as a result of stable integration events, but also through accompanying events that do not result in major changes in the mutated loci. The nature of these changes at the molecular level remains to be elucidated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01973592
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  • 44
    Electronic Resource
    Electronic Resource
    An assessment of gene transfer by pollen from field-grown transgenic potatoes to non-transgenic potatoes and related species (1994)
    Springer
    Transgenic research 3 (1994), S. 216-225 
    Details
    ISSN: 1573-9368
    Keywords: Solanum tuberosum ; genetic modification ; transformation ; gene transfer ; genetic isolation ; risk assessment
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Information on the extent of transgene dispersal by pollen to adjacent potato plots and to related weed species is an important requisite for risk assessment; a procedure followed before novel transgenic plants are evaluated under field conditions. The purpose of the investigation was to determine the frequency of cross-pollination between potato (Solanum tuberosum) plants at different distances, using a kanamycin resistnace transgene (nptII) as a selectable marker. All potato plants were from the variety Désirée. Non-transgenic potato plants, used as potential recipients of transgene-containing pollen, were planted in 12 sub-plots, at distances of 0–20 m from the nearest transgenic potato plants. Seeds harvested from the non-transgenic plants were screened for resistance to kanamycin, and molecular methods were used to confirm that resistant progeny contained thenptII gene. Where transgenic and non-transgenic potato plants were in alternate rows (leaves touching), 24% of seedlings from the non-transgenic parent plants were kanamycin-resistant. Comparable seedlings from plants at up to 3 m distance had a resistance frequency of 2%, at 10 m the frequency was 0.017% and at 20 m no resistant progeny were observed. Plants of the weed speciesS. dulcamara andS. nigrum were also planted close to the transgenic potatoes to test for evidence of hybridization, and no kanamycin-resistant seedlings were observed among progeny fromS. dulcamara andS. nigrum. This investigation provided evidence that the extent of gene dispersal from transgenic potatoes to non-transgenic potatoes falls markedly with increasing distance, and is negligible at 10 m. There was, also, no evidence of transgene movement from potato toS. dulcamara andS. nigrum under field conditions. These data will be valuable in defining genetic isolation procedures for the early field evaluation and the use of novel transgenic potato genotypes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02336774
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  • 45
    Electronic Resource
    Electronic Resource
    Recombinant viruses as transformation vectors of marine macroalgae (1994)
    Springer
    Journal of applied phycology 6 (1994), S. 247-253 
    Details
    ISSN: 1573-5176
    Keywords: algae ; genes ; recombinant ; transformation ; vectors ; viruses
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The large dsDNA viruses that are known to infect eukaryotic algae show promise as genetic vectors for algal biotechnology. The large size (150–330 kbp) of these viral genomes may permit insertion of large sequences of foreign DNA. The viruses infecting filamentous marine brown algae appear to be integrated into the genomes of their hosts, and may provide integration mechanisms that can be used for directing insertion of foreign genes into algal chromosomes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02186078
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  • 46
    Electronic Resource
    Electronic Resource
    Maintenance and expression of heterologous genes in chloroplast ofChlamydomonas reinhardtii (1994)
    Springer
    Journal of applied phycology 6 (1994), S. 239-245 
    Details
    ISSN: 1573-5176
    Keywords: Chlamydomonas reinhardtii ; transformation ; chloroplast ; aminoglycoside adenine transferase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The chloroplast genome ofChlamydomonas reinhardtii has been transformed with a chimeric gene consisting of the chloroplastatpA promoter and the bacterial gene for aminoglycoside adenine transferase (aadA). TheatpA-aadA cassette has been placed within the chloroplast DNAEcoRI restriction enzyme fragment 14, or within the chloroplastBamH1 fragment 10. The chimeric constructs were introduced into the chloroplast by particle bombardment. Integration of the cassette into chloroplast DNA then occurred via homologous recombination of sequences flanking the cassette with their corresponding chloroplast sequences. We demonstrate that the chloroplastatpA promoter inatpA-aadA routinely recombines with its endogenous counterpart, resulting in heteroplasmic chloroplast DNA populations that may persist for many generations. The heterologous gene does not require a 3′ inverted repeat sequence for its expression. TheatpA-aadA gene copy number, which is dictated here by its position in the chloroplast genome, is proportional to the steady state level ofatpA-aadA mRNA. However, neither genomic position, gene copy number, or mRNA level have a significant effect on cellular resistance to spectinomycin, nor activity of theaadA gene productin vitro. These results suggest that, in the case ofaadA, the limiting step for expression of this gene is at the translational or post-translational level. TheatpA-aadA cassette should prove a useful model for future studies on the maintenance and expression of heterologous genes inC. reinhardtii chloroplasts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02186077
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  • 47
    Electronic Resource
    Electronic Resource
    A simple technique for producing 13C or 14C-labelled fronds of Lemna gibba and their use in soil incubation investigations (1994)
    Springer
    Plant and soil 160 (1994), S. 185-191 
    Details
    ISSN: 1573-5036
    Keywords: carbon-labelling ; carbon dioxide production ; decomposition ; 14C-glucose ; Lemna ; soil organic matter ; sugars ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The duckweed Lemna gibba required light and a suitable energy source such as sucrose, glucose or fructose, for maximum growth in culture. The requirement for light was relatively unimportant and the plants grew well in a photon flux density of only 52 μmol m-2s-1 PAR. The uptake and incorporation of uniformly labelled 14C-glucose into fronds was related only to the concentration of the sugar. When incubated with soil, labelled L. gibba behaved in a manner similar to that of labelled ryegrass roots which had been produced by a more elaborate technique using a 14CO2 labelled atmosphere. During incubation with soil for 224 days the L. gibba material (specific activity 6133 Bq mg-1 d. wt) lost 64% of its radioactivity as 14CO2 and ryegrass (specific activity 6634 Bq mg-1 d. wt) lost 49%. Alkaline extracted humic and fulvic acids from soil had specific activities for the L. gibba incubation of 3409 and 407 Bq mg-1 solid and for ryegrass roots of 4609 and 546 Bq mg-1 solid respectively. The production of 13C or 14C-labelled L. gibba can be undertaken using only simple equipment producing material the specific radioactivity of which can be controlled by adjusting the activity of the sugar energy source.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010144
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  • 48
    Electronic Resource
    Electronic Resource
    A robust protocol for site-directed mutagenesis of the D1 protein inChlamydomonas reinhardtii: A PCR-splicedpsbA gene in a plasmid conferring spectinomycin resistance was introduced into apsbA deletion strain (1994)
    Springer
    Photosynthesis research 42 (1994), S. 121-131 
    Details
    ISSN: 1573-5079
    Keywords: chloroplast ; Photosystem II ; psbA ; site-directed mutagenesis ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this paper, we describe a protocol to obtain a site-directed mutants in thepsbA gene ofChlamydomonas reinhardtii, which overcomes several drawbacks of previous protocols, and makes it possible to generate a mutant within a month. Since the large size of the gene, and the presence of four large introns has made molecular genetics of thepsbA gene rather unwieldy, we have spliced all of the exons of thepsbA gene by PCR to facilitate genetic manipulation and sequencing of the gene. The resultant construct (plasmid pBA153, with several unique restriction sites introduced at exon boundaries) carried 1.2 and 1.8 kb intact sequences from the 5′- and 3′-flanking regions, respectively. The plasmid was used to transform a D1-deletion mutant and was found to complement the deletion and restore photosynthetic activity. In addition, a bacterialaadA gene conferring spectinomycin resistance (spe r) was inserted downstream of the intron-freepsbA gene, to give construct pBA155. This allowed selection of mutant strains deficient in photosynthesis by using spectinomycin resistance, and eliminated the possibility of selection for revertant strains which is a consequence of having to use photosynthetic activity as a selection pressure. Finally, pBA155 was used to construct pBA157, in which additional restriction sites were inserted to facilitate cassette mutagenesis for generation of mutations in spans thought to be involved in donor-side interactions. AllpsbA deletion strains transformed with intron-freepsbA-aadA constructs encoding the wild-type D1 sequence, and screened on spectinomycin plates for thespe r phenotype, were able to grow photosynthetically, and all showed identical kinetics for electron transfer from primary (QA) to secondary quinone (QB) in Photosystem II, as assayed by the decay of the high fluorescence yield on oxidation of the reduced primary acceptor (QA −).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02187123
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  • 49
    Electronic Resource
    Electronic Resource
    Some features about transposition of the maize elementDissociation inNicotiana plumbaginifolia (1994)
    Springer
    Genetica 93 (1994), S. 41-48 
    Details
    ISSN: 1573-6857
    Keywords: Ac/Ds ; transformation ; transgenic plants ; transposon tagging
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have recently shown that a plasmid-borneDissociation (Ds) element can excise from extrachromosomal plasmid DNA and integrate into a plant genome in the presence of theActivator (Ac) transposase.Ds andAc-carrying plasmids were used to co-transformNicotiana plumbaginifolia protoplasts. Transgenic plants were regenerated and analyzed. Here we describe further characterization of the system and discuss its efficiency in terms of DNA transformation and transposon tagging.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01435238
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  • 50
    Electronic Resource
    Electronic Resource
    Transmission of injected DNA sequences to multiple eggs of Metaseiulus occidentalis and Amblyseius finlandicus (Acari: Phytoseiidae) following maternal microinjection (1994)
    Springer
    Experimental and applied acarology 18 (1994), S. 319-330 
    Details
    ISSN: 1572-9702
    Keywords: Maternal microinjection ; transformation ; genetic improvement
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The persistence of DNA injected into two species of adult female phytoseiids and its transmission to serial eggs deposited by them was assessed by the polymerase chain reaction (PCR). The effect of DNA concentration on persistence and transmission was examined in Metaseiulus occidentalis. M. occidentalis females were microinjected with plasmid DNA at three different concentrations (250, 500, 750 ng μL−1) and allowed to deposit one to five eggs before the females and their last eggs were analyzed. Plasmid DNA was found in 82% of the females assayed and in 70% of all the eggs analyzed (including the fifth eggs produced after microinjection). Transmission of DNA to multiple eggs was also examined in Amblyseius finlandicus. Females of this species are less traumatized by microinjection allowing analysis of transmission over a more extended number of eggs. Females were microinjected and allowed to deposit eggs until their death. DNA from every fifth egg was analyzed by the PCR. PCR products were amplified from 51% of the eggs and from all egg classes except the 30th egg. The persistence and presence of plasmid DNA in both eggs and females suggests that (1) maternal microinjection is a more efficient method for DNA delivery than traditional egg microinjection, (2) it may be possible to isolate transformants from fewer maternally-microinjected females than originally expected, and (3) maternal microinjection could be useful as a DNA delivery system in other phytoseiids.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00116313
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  • 51
    Electronic Resource
    Electronic Resource
    Genetics and gibberellin production inGibberella fujikuroi (1994)
    Springer
    Antonie van Leeuwenhoek 65 (1994), S. 217-225 
    Details
    ISSN: 1572-9699
    Keywords: Gibberella fujikuroi ; gibberellins ; mutants ; regulation by nitrogen ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gibberella fujikuroi (Fusarium moniliforme) is a complex group of plant pathogens. Some strains produce gibberellic acid and other gibberellins that promote growth and regulate various stages in plant development. The paper describes the research effort directed to development of genetic tools for this species. Furthermore the main features of the gibberellin biosynthetic pathway as established in Gibberella are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00871950
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  • 52
    Electronic Resource
    Electronic Resource
    Stably transformed cell lines from protoplasts of maize endosperm suspension cultures (1994)
    Springer
    Plant cell, tissue and organ culture 37 (1994), S. 39-46 
    Details
    ISSN: 1573-5044
    Keywords: endosperm cell culture ; maize ; protoplast ; transformation ; zeins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Protoplasts were isolated from Zea mays (L.) A69Y endosperm suspension cultures and transformed by polyethylene glycol mediated DNA uptake with chimaeric gene constructs containing β-glucuronidase (GUS) or neomycin phosphotransferase II (NPTII); GUS-expressing and Kanamycin-resistant cultures were recovered. The transformed cells showed integration of the introduced foreign genes into genomic DNA and maintained their ability to synthesize endosperm-specific reserve proteins (zeins). No deletion or rearrangement of zein genes were observed in transformed cultures. Stable transformation of cultured maize endosperm cells may therefore represent a new methodological approach for the study of the transcriptional regulation of endosperm-expressed genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00048115
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  • 53
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    Electronic Resource
    Efficient plant regeneration through somatic embryogenesis from callus induced on mature rice embryos (Oryza sativa L.) (1994)
    Springer
    Plant cell, tissue and organ culture 36 (1994), S. 259-264 
    Details
    ISSN: 1573-5044
    Keywords: monocotyledons ; Oryza sativa L. ; plant regeneration ; rice ; somatic embryogenesis ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To obtain a reproducible efficient procedure for regeneration of rice plants through somatic embryogenesis from callus four published methods of callus induction and regeneration were compared. Callus was initiated from mature embryos of the Japonica cultivar Taipei 309 of rice (Oryza sativa L.). The number, mass and morphology of the callus formed on the scutellum were dependent on the medium used. A limited humidity and an optimal aeration of the culture vessels enhanced the frequency of embryogenesis and plant regeneration. A method described by Poonsapaya et al. (1989) was found to be the most efficient and was slightly modified. As a result 98% of the T309 embryos formed callus, of which 63% regenerated into plants. Each callus yielded an average of 6 plants. Plant morphology, fertility and seed set of the regenerants were found to be normal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00037729
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  • 54
    Electronic Resource
    Electronic Resource
    Factors that effect leaf regeneration efficiency in apple, and effect of antibiotics in morphogenesis (1994)
    Springer
    Plant cell, tissue and organ culture 37 (1994), S. 257-269 
    Details
    ISSN: 1573-5044
    Keywords: adventitious shoots ; Malus x domestica Borkh. ; tissue culture ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several factors that affect the frequency of organogenesis in apple leaf explants were examined for the scion cultivars ‘Empire’, ‘Freedom’, ‘Golden Delicious’, ‘Liberty’, ‘McIntosh’, and ‘Mutsu’ and for the rootstocks Malling 7A and Malling 26. The main factors affecting morphogenesis were BA concentration, basal medium, leaf explant origin and maturity, explant orientation, and photosynthetic photon flux. Depending on the genotype, optimal regeneration was obtained using either 22.2 or 31.1 μM BA and the N6 basal medium, with the exception of ‘Golden Delicious’ which regenerated better on MS medium. After 6 weeks, the average number of shoots per segment varied from 5 to 16, and the percentage of regeneration between 70 and 100%, depending on the genotype tested and the maturity of the explant. Regeneration capacity increased dramatically from the tip towards the base of the leaf, and was higher from the middle to the proximal end. Cefotaxime and carbenicillin, two antibiotics commonly used during transformation studies to eliminate Agrobacterium tumefaciens from plant tissue, were tested to determine their effect on morphogenesis. Cefotaxime at a dose of 250 mg 1-1 enhanced regeneration and shoot development, whereas carbenicillin at a dose of 500 mg l-1 induced abundant callus formation and inhibited regeneration. Kanamycin, a widely used selection agent for plant transformation, strongly inhibited regeneration even at very low doses. Schemes for selection and recovery of transgenic apple plants when kanamycin is used as the selection agent are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00042339
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  • 55
    Electronic Resource
    Electronic Resource
    Micropropagation of thirteen Malus cultivars and rootstocks, and effect of antibiotics on proliferation (1994)
    Springer
    Plant growth regulation 15 (1994), S. 55-67 
    Details
    ISSN: 1573-5087
    Keywords: apple (Malus × domestica Borkh.) ; selection ; tissue culture ; transformation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Several factors that affect in vitro establishment, proliferation, and rooting of thirteen Malus cultivars and rootstocks were studied. Apple shoot tips (1.5±0.5 cm in length) were established using ascorbic and citric acids as antioxidants. Four proliferation media containing 1.0 mg 1−1 BA and different concentrations of IBA and GA3 were tested. Proliferation rates varied depending on the genotype and medium used. The highest proliferation rate was obtained for a rootstock that produced 11.6±2.5 shoots (1.5±0.8 cm in length) per tube per month. Rooting was induced with IBA for all the genotypes tested. The optimal IBA concentration was cultivar dependent (between 0.1 and 1.0 mg 1−1 IBA), and lower concentrations were necessary to induce rooting in liquid rather than in solid medium. The effects on shoot-tip proliferation of cefotaxime, carbenicillin and kanamycin, three antibiotics commonly used for transformation studies, were also evaluated. Cefotaxime at 200 mg 1−1 stimulated shoot growth and development, but at 500 mg 1−1 caused abnormal shoot morphology. Carbenicillin at 500 mg 1−1, alone or in combination with cefotaxime at 200 mg 1−1, inhibited proliferation and caused excessive enlargement of the basal leaves, inducing callus formation and release of phenolic compounds in the medium. Kanamycin at 50 mg 1−1 was phytotoxic and caused shoot chlorosis and necrosis. Consideration of the toxicity of these antibiotics is critical when designing transformation schemes for selection and recovery of transgenic apple plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024677
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  • 56
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    Electronic Resource
    Nitrostyrene Derivatives of Adenosine 5′-Glutarates Modified with an Alkyl Spacer and their inhibitory activity on epidermal growth factor receptor protein tyrosine kinase (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 59-69 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: β-Nitrostyrene derivatives of adenosine 5′-glutarates are potent and selective bisubstrate-type inhibitors of the epidermal growth factor receptor protein tyrosine kinase (EGF-R PTK). In an attempt to improve the inhibitory activity, this type of compounds was modified with alkyl spacers of varying length between the nitrostyrene and the glutaryl units. The spacers consisted of 1, 3, 4, and 5 atoms to give compounds of the benzyl, oxyethyl, oxypropyl, and oxybutyl series, respectively (Schemes 1 and 2). Adenosine 5′-esters were prepared in the benzyl and oxypropyl series only. Compared to the compounds in the parent series without spacer (IC50 = 0.7-12 μM), most of the modified compounds inhibited the EGF-R PTK only marginally or were inactive (IC50 ≥ 100 μM). The only exceptions were the free acids 19 and 20 with IC50 values of ca. 5 μM. It is noteworthy that esterification of these two hydrogen glutarates with either MeOH or adenosine yielded inactive compounds, which is in contrast to the corresponding substances without spacers.
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    Synthese und Eigenschaften der Furo- und Thieno-Analogen von PQQ-TriesterTeil einer Präsentation am ‘2nd International Symposium on PQQ and Quinoproteins’, 19.-22. Nov. 1991, Yamaguchi, Japan. (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 100-110 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Characterization of the Furo and Thieno Analogues of the Triester of PQQWe report here the synthesis and properties of the furo and thieno analogues of 4,5-dihydro-4,5-dioxo-1H-pyrrolo[2,3-f]quinoline-2,7,9- tricarboxylic acid ( = PQQ), i.e. the furo- and thieno[2,3-f]quinoline-4,5-quinone (FQQ and TQQ, resp.) derivatives B and C, obtained as triesters. The triester of PQQ derivative A is much more stable than the triesters of B or C, and only the triester of A shows strong activity in nonenzymatic catalytic oxidations.
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    URL: http://dx.doi.org/10.1002/hlca.19940770113
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    Computational Approach to the Receptor-Bound Conformation of Cyclosporin A (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 171-181 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conversion of the conformation of cyclosporin A (CsA) observed in CHCl3 to the receptor-bound state is investigated by two molecular-mechanics methods, template forcing and dynamic forcing. The conformations of CsA in CHCl3 and complexed with LiCl in THF as determined by NMR are used as starting structures. The transition starting from the CsA/CHCl3-derived conformation is hindered by steric interactions of two side chains (MeBmt1 and Val5). While starting with the CsA/LiCl-derived conformation, the conversion is facile. It is illustrated that these calculations, which are of artificial character, using only the starting and final structures of the observed conformational transition during the receptor-binding event, allow an insight into the interactions between the substrates and receptor in terms of an induced fit.
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    URL: http://dx.doi.org/10.1002/hlca.19940770120
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  • 59
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    Electrochemical Study of Phase-Transfer Catalysis Reactions: The Williamson ether synthesis (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 231-242 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The transfer properties of the ionic species involved in the Williamson ether synthesis by phase-transfer catalysis were investigated using electrochemical techniques developed for the study of polarised liquid/liquid interfaces. This approach allows the measurement of the apparent partition coefficients of the transferring species. From these data, it is proposed that the role of the phase-transfer catalyst salt in the reaction mechanism is to establish a Galvani distribution potential difference between the two phases which in turn acts as the driving force for transferring the reactive aqueous ions to the organic phase.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19940770125
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  • 60
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    Synthesis of (R)- and (S)-5-(Hydroxymethyl)-3-isopropyloxazolidin-2-one, intermediates in the preparation of optically active β-blockers (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 252-256 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The (R)- and (S)-5-(hydroxymethyl)-3-isopropyloxazolidin-2-ones, ((R)- and (S)-2, resp.), pivotal intermediates in the preparation of optically active β-blockers, were synthesized using (R,E)-2-hydroxypent-3-enenitrile (1) as the chiral starting material. In the synthesis of (R)-2, a known cyclization/inversion step was applied.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770127
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  • 61
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    Calorimetric Measurements of the Complexation of Cyclosporin A, Ascomycin, Fujimycin, and Rapamycin with Lithium Chloride and with an Immunophilin (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 291-305 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Solutions (2 ml) of small linear and cyclic peptides (4-11), of a peptolide containing nine amino acids and a lactate moiety (12), of the cyclic undecapeptide cyclosporin A (CS, 1), and of the macrolides ascomycin, fujimycin, and rapamycin (13-15) in THF were added to excess LiCl, LiBr, or LiClO4 (up to 3000 equiv. in 40 ml THF) in a calorimeter (calorimetric titration). The enthalpies of interaction measured are in the range of ΔH = -8 to -37 kcal/mol. A similar experiment was carried out with one of the binding proteins of cyclosporin, the human cyclophilin A, to give the thermodynamic parameters for the complexation ΔH = -16, ΔG° = -10 kcal/mol, and ΔS° = -20 cal/mol·deg. at 25° which corresponds to an equilibrium constant K = 2·107 l/mol, in good agreement with the result of independent measurements using different methods. NMR Measurements of the macrolides in (D8)THF containing LiCl show strong down-field shifts of signals of the H-atoms next to C=O and C-OH groups in these molecules.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19940770129
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  • 62
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    NMR of Terminal Oxygen. Part 13Part 12: [1].. 17O-NMR spectra of C-nitroso compounds, thionitrites and NO+ Ion: Resonance effects in O=N - X compounds and correlation with CD spectra (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 306-316 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 17O-NMR signals of four true C-nitroso compounds 1-4 appear at particularly low field (1550-1265 ppm), whereas the dimers (azodioxy type) resonate at ca. 400 ppm and the ‘isonitroso compounds’ ( = quinone-oximes; 5 and 6) at ca. 250 ppm. S-Nitroso compounds ( = thionitrites; 8 and 9) show shift values of ca. 1300 ppm, not far from C - NO; the NO+ ion is much stronger shielded (474 ppm). The results, together with those for higher-shielded nitroso compounds X - NO (X = RO, R2N, Cl, O-) are discussed in terms of (a) resonance stabilization through n-donation from X(π-bond order, approximated by the known barriers of rotation around the X - N bond) and of (b) electronic excitation energies ΔE. The latter are approximated by long-wave (symmetry-forbidden) UV/VIS absorptions and confirmed, where available, by the maxima of the curves of circular dichroism (CD); the CD curve of thionitrite 9 has been measured. It is found that the δ(17O) values of X - NO depend both on bond order and on ΔE, which could not be separated. The higher shielding of NO+ compared with X - N=O is explained on the basis of anisotropy effects, which differ between sp and sp2 systems.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19940770130
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770101
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    Enantioselective synthesis of (-)-conduramine C1 and aminobromocyclitol derivatives‘Naked Sugars’ as Synthetic Intermediates, Part XXV. Part XXIV, see [1a]; Part XXIII, see [1b]. (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1-9 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (1S,2R,6R,7R)-4-Phenyl-3,10-dioxa-5-azatricyclo[5.2.1.02,6]dec-4-en-9-one ((+)-5) obtained in 6 steps from the Diels-Alder adduct of furan to 1-cyanovinyl (1S)-camphanate ((+)-3) was reduced to the corresponding endo-alcohol (-)-6 the treatment of which with HBr/AcOH provided (-)-(3aS,4S,6R,7S,7aR)-4β-bromo-3aβ,4,5,6,7,7aβ-hexahydro-2-phenyl-1,3-benzoxazole-6β,7α-diyl diacetate ((-)-17). Elimination of HBr with 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) and acidic hydrolysis furnished (-)-(1R,2S,3R,4R)-4-aminocyclohex-5-ene-1,2,3-triol ( = (-)-conduramine C1;(-)-1).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770103
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    Nucleotides Part XLPart XXXIX: [1].. Synthesis and Characterization of Modified 2′-5′ Adenylate Trimers-Potential Antiviral Agents (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 10-22 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 2′-5′ Adenylate trimers 41-44 carrying the (tert-butyl)dimethylsilyl (tbds) group at the 3′-OH position of various sugar moieties were synthesized via the phosphoramidite method. The use of the (tert-butyloxy)carbonyl (boc) and 2-(4-nitrophenyl)ethylsulfonyl (npes) groups for 2′-OH protection in neighbourhood to the 3′-O-tbds residue was compared during the synthesis of the target trimers. For other functional positions, the use of the 2-(4-nitrophenyl)ethyl (npe) and 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) blocking groups were favoured.
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    URL: http://dx.doi.org/10.1002/hlca.19940770104
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    Metal complexes of macrocyclic ligands. Part XXXVIIPart XXXVI: [1].. Synthesis of Heteroditopic Bis-macrocycles and Their Potential for Preparing Heterobinuclear Metal Complexes (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 23-35 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new and generally applicable synthetic path for the preparation of heteroditopic bis-macrocycles using tri-N-protected tetraazacycloalkanes as building blocks and bromoacetyl bromide as bridging reagent is described. In the first step, bromoacetyl bromide is used as acylating agent for one of the macrocycles, whereas in the second step it is used as alkylating agent for the second macrocycle, thus giving protected bis-macrocyclic amides (e.g. 6). After reduction of the amide moiety and deprotection, bis-azamacrocycles with an ethylene bridge are obtained (e.g. 8). The corresponding homoditopic bis-macrocycles 16 and 17 are also prepared for comparison purpose. Spectrophotometric studies indicate that bis-macrocycle 8, which consists of a 12- and a 14-membered ring, binds two metal ions with equal affinity, whereas compound 13, in which an unsubstituted (cyclam) and a trimethyl-substituted tetraazacyclotetradecane unit (Me3cyclam) are bridged, shows selective metal-ion binding. The first metal ion is always incorporated into the cyclam unit, whereas the second one binds to the Me3cyclam macrocycle. Thus, by sequential addition of two different metal ions, heterobinuclear complexes can easily be prepared. The electrochemistry of the binuclear Ni2+ complexes, studied by CV and DPV, as well as the EPR spectra of the binuclear Cu2+ complexes clearly indicate metal-metal interactions.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19940770105
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    Thermoconversion of Caryophyllene- to Farnesene-Type Sesquiterpenes. Short access to the enantiomers of (6RS,7RS)- and (6RS,7SR)-6,7-epoxy-6,7-dihydro-β-farnesenes (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 36-40 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Flash-vacuum thermolysis of the four diastereoisomeric 5,6-epoxy-5,6-dihydro-caryophyllenes 1-4 at 500-550°/0.1-0.7 Torr leads to the hitherto unreported enantiomers of (6RS,7RS)- and (6RS,7SR)-6,7-epoxy-6,7-dihydro-β-farnesenes ((±)-5 and (±)-6, resp.). In particular, (+)-5 is formed in 45% yield (ca. 90% ee) and is, thus, an attractive chiral building block for natural-product synthesis.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19940770106
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  • 68
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    Oceanapins A-F, Unique Branched Ceramides Isolated from the Haplosclerid Sponge Oceanapia cf. tenuis of the Coral SeaDedicated to the memory of Margherita Ratti (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 51-58 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of ceramides, called oceanapins A-F (2-7), which are unique for branching at both the sphingosine and fatty-acid chains, have been isolated as pure compounds from the haplosclerid sponge Oceanapia cf. tenuis of the Coral Sea. Following acid hydrolysis, both the fatty-acid and the sphingosine portions were obtained separately, which allowed their unequivocal structural definition. The absolute configuration was secured via protection of C(1′)-OH and Mosher's esterification at C(3′)-OH of the oceanapins.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19940770108
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    Single-Crystal Structure of the Solvent-Separated Radical Ion Pair [9,10-diphenylanthracene.⊖][Na⊕(THF)6] and its implication for cation solvationDedicated to Peter Weyerstahl on the occasion of his 60th birthdayPart 26 of ‘Structures of Charge-Perturbed or Sterically Overcrowded Molecules’; Part 25: [1]. (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 41-50 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The one-electron transfer to large π-delocalized hydrocarbons provides an interesting possibility to crystallize solvent-separated ion-pair salts containing optimally solvated cations. Accordingly, the reduction of 9,10-diphenylanthracene in aprotic THF solution at a sodium metal mirror allows to grow dark-blue prismatic crystals of its radical anion and sixfold THF-solvated sodium cation. The structure of the radical anion is very similar to that recently published for the neutral molecule. According to AM1 hypersurface calculations based on the structural data, the phenyl twist angles obviously must be determined by lattice packing, and the negative charge is delocalized predominantly within the anthracene π system. The counter cation [Na⊕(THF)6], reported ordered for the first time, shows nearly octahedral coordination within a rather densily packed solvent shell. Due to the strong repulsions between the solvent molecules, its isodesmically calculated solvation enthalpy is smaller than that of the analogous dimethoxyethane complex [Na⊕(DME)3].
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19940770107
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    Radical Cations of Tetrazinodi(heteroarenes): An ESR and ENDOR Study (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 86-91 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 14N- and 1H-Coupling constants, determined by ESR, ENDOR, and general-TRIPLE-resonance spectroscopy, are reported for the radical cations of tetrazinodi(heteroarenes) 1-8. The results comply with the expectation that donor properties of these compounds are mainly due to the electron-rich dihydrotetrazine ring.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19940770111
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    Antiparallel β-Sheet Conformation in Cyclopeptides Containing a Pseudo-amino Acid with a biphenyl moiety (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 70-85 
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    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The biphenyl-containing pseudo-amino acids 2′-(aminomethyl)biphenyl-2-carboxylic acid (Abc; 1) and 2′-(aminomethyl)biphenyl-2-acetic acid (Aba; 2) are used as rigid spacers in the backbone of the cyclic peptides cyclo (-Abc-Ala-Phe-Gly-)2 (5), cyclo(-Abc-Ala-Val-Gly-)2 (6), cyclo(-Aba-Gly-Phe-Ala-)2 (7), and cyclo(-Aba-Ala-Phe-Gly-)2(8). Three different interconverting diastereoisomers are found in solutions of each of these cyclopeptides due to the atropisomerism of the biphenyl units. NMR Techniques and molecular-dynamics calculations allow to conclude that the major diastereoisomer of 5 (and 6) in (D6)DMSO adopts a β-sheet conformation. It is proposed that the pseudo-amino acid 1 of (R)-chirality forms, with attached L-amino acids, a H-bonding pattern comparable to a β-turn (see D in Fig. 4 and F).
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19940770110
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    Vitamin-B12-katalysierte C,C-Bindungsverknüpfung: Synthese von Jasmonaten via sequentielle Radikal-Reaktion (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 92-99 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vitamin-B12-Catalyzed C, C-Bond Formation: Synthesis of Jasmonates via Sequential Radical ReactionThe Cbl-catalyzed electroreduction of 3-(2′-bromo-1′-ethoxyethoxy)cyclopenten (1a) in presence of 1-cyanovinyl-acetate (8) gave, in a sequential radical reaction (5-exo-trig-cyclization of 1a followed by addition to 8), 1-cyano-2-(2′-ethoxy-hexahydro-2′H-cyclopenta[b] furan-4′-yl)ethyl acetate (10a). This intermediate was transformed to methyl jasmonate (7; four steps) and epituberolide (9; three steps) in 20 and 31% yield, respectively, from cyclopent-2-en-l-ol.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770112
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    Die Synthese von Azaisomeren des Triesters von PQQ: 3H-Pyrrolo[3,2-f]-, 1H-Pyrrolo[3,2-h]- und 7H-Pyrrolo[2,3-h]chinolinchinon-Derivate (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 111-120 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The Synthesis of Azaisomers of the Triester of PQQ: 3H-Pyrrolo[3,2-f]-, 1H-Pyrrolo[3,2-h]-, and 7H-Pyrrolo[2,3-h]quinolinequinone DerivativesWe describe here the synthesis of the title compounds 3-5, starting from highly substituted aminoindoles. The annelated pyridine rings were built up in each case with dimethyl 4-oxoglutaconate according to Corey's procedure. All three o-quinone derivatives 3-5 are stable compounds, comparable to PQQ-triester. The azaisomers vary in biological activity from practically inactive to strong inhibition of the α-amidating enzyme or the ornithin decarboxylase.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19940770114
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    A Novel Approach to 2,2-Disubstituted 1,2-Dihydro-4-phenylquinolines (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 608-614 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of 2-(1-phenylvinyl)aniline and 4-chloro-2-(1-phenylvinyl)aniline with acetophenone derivatives, 1-(naphthalen-1-yl)ethanone and 1-(furan-2-yl)ethanone in toluene at 110-115° with toluene-4-sulfonic acid as a catalyst leads in good-to-excellent yields to the 2,2-disubstituted 1,2-dihydro-4-phenyl-quinolines 1-18 (Scheme 1, Table). The structure of the new racemic 1,2-dihydroquinolines 1-18 is determined by NMR spectroscopy. A reaction mechanism proceeding via a 6π-electrocyclic rearrangement of 2-(1-phenylvinyl)anils 19 as the key step is proposed for the formation of these compounds (Scheme 1). The scope and limitations of the novel methods are discussed (Scheme 2).
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19940770303
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    Facile Synthesis of 2′-Deoxyisoguanosine and Related 2′,3′-Dideoxyribonucleosides (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 622-630 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 2′-deoxyisoguanosine (1) was synthesized by a two-step procedure from 2′-deoxyguanosine (5). Amination of silylated 2′-deoxyguanosine yielded 2-amino-2′-deoxyadenosine (6) which was subjected to selective deamination of the 2-NH2 group resulting in compound 1. Also 2′,3′-dideoxyisoguanosine (2) was prepared employing the photo-substitution of the 2-substituent of 2-chloro-2′,3′-dideoxyadenosine (4). The latter was synthesized by Barton deoxygenation from 2-chloro-2′-deoxyadenosine (3) or via glycosylation of 2,6-dichloropurine (12) with the lactol 13. Compound 1 was less stable at the N-glycosylic bond than 2′-deoxyguanosine (5). The dideoxynucleoside 2 was deaminated by adenosine deaminase affording 2′,3′-dideoxyxanthosine (17).
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    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770305
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  • 76
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    Derivatives of (2R)-N-Glyoxylbornane-10,2-sultam and Their Use as auxiliaries in the diastereoselective spirocyclization of 2-substituted tryptamines7th Communication on ‘Indoles, Indolenines, and Indolines’; 6th communication: [1]. (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 615-621 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A crude hydrate 6 and a crystalline hemiacetal 7 of glyoxylamide 4 were prepared from crotonamide 5 (Scheme 2). Particularly hemiacetal 7, but also 6 and the ‘dimer’ 8 (obtained from 7) may serve as homochiral auxiliaries. The structure of 8 was determined by X-ray analysis. By arenesulfonyl halides, tryptimines 12-14 of 4 were diastereoselectively transformed into spirotricycles 15-17 and 19.
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    URL: http://dx.doi.org/10.1002/hlca.19940770304
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  • 77
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    Synthesis and Conformational Analysis of 2′-Deoxy-2′-(3-methoxybenzamido)adenosine, a rational-designed inhibitor of trypanosomal glyceraldehyde phosphate dehydrogenase (GAPDH) (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 631-644 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A series of 2′-benzamido-2′-deoxyadenosine analogues were synthesized in an effort to find new lead structures for the treatment of sleeping sickness. The 2′-deoxy-2′-(3-methoxybenzamido)adenosine (1h) was proved to be a selective inhibitor of the parasite glyceraldehyde 3-phosphate dehydrogenase which confirms the modeling studies. The solution-state conformation of 2′-(thiophene-2-carboxamido) analogue 1d demonstrates a 2′-endo conformation, an orientation of the thiophene ring under the ribose moiety, and the base part occupying a ‘syn’/‘anti’ equilibrium.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19940770306
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  • 78
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    Enantioselective Formation of Bicyclic Lactones by Rhodium-Catalyzed Intramolecular CH-insertion reactions (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 645-654 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The decomposition of cyclohexyl diazoacetate (5a) in the presence of the chiral [Rh2{(2S)-mepy}4] catalyst leads to a 3:1 cis/trans mixture of bicyclic lactone 6a with an enantiomeric excess of 95-97% (cis) and 90% (trans). The conformationally rigid tert-butyl derivatives 5b and 5c afford, in the presence of the same catalyst, 6b and 6c, respectively, via insertion into the equatorial C—H bonds exclusively, with ee's of ca. 95%. A remarkable degree of induction (92-95%) results in the lactone 6g upon decomposition of 1-isopropyl-2-methylpropyl diazoacetate (5g). The diazoacetates derived from 1-methylcyclohexanol, cyclopentanol and 1-methylcyclopentanol (5d-f) afford under similar conditions insertion products with higher diastereoselectivity, but significantly lower enantioselectivity. Other dirhodium catalysts are less efficient.
    Additional Material: 2 Tab.
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  • 79
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    A Concise Synthesis of (E)- and (Z)-Neomanoalides (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 661-667 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The first synthesis of (Z)-neomanoalide (4) and an improved synthesis of its (E)-isomer 3 was accomplished in a concise, regiocontrolled manner by exploiting 2-[(tert-butyl)dimethylsiloxy]-4{[(tert-butyl)dimethylsiloxy]-methyl}furan (6) as the key reagent. Lithiation of 6 and subsequent reaction with the (2Z)- or (2E)-isomer of (6E)-3-{[(tert-butyl)dimethylsiloxy]methyl}-7-methyl-9-(2′,6′,6′-trimethylcyclohex-1′-enyl)nona-2,6-dienyl bromide (5), followed by hydrolysis, afforded the corresponding neomanoalide.
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    URL: http://dx.doi.org/10.1002/hlca.19940770309
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  • 80
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    Stable Quinone Methides: Regioselective para-Oxidation of a 2,4-bis[(alkylthio)methyl]phenol and addition reactions to quinonemethides (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 655-660 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The 2,4-bis-functionalized phenol 1 is dehydrogenated regioselectivity with potassium ferricyanide, affording the corresponding p-quinonemethide 2. Hydrolysis of 2 affords a mixture of dithioacetal 5a and benzaldehyde 6; 1,6-addition of thiols to 2 gives the dithioacetals 5 of benzaldehyde 6; reaction of 2 with 2,2′-azobis(isobutyronitrile) (= 2,2′-dimethyl-2,2′-azobis(propanenitrile)) leads to 9a, 9b, and 10, addition products of the 1-cyano-1-methylethyl radical. The structures of all products are confirmed mainly by 1H- and 13C-NMR spectroscopy, and the mode of their formation is discussed.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19940770308
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  • 81
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    Oligosaccharides Related to Tumor-Associate Antigens. Part 2Part 1: [1].. Conformational analysis of the trisaccharide α-L-Fucp-(1→2)-β-D-Galp-(1→3)-β-D-GalpNAc, epitope structure recognized by the MBr1 antibody (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 668-678 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational space of the trisaccharide α-L-Fuc-(1→2)-β- D-Gal-(1→3)-β -D-GalNAc-1-OPr (2) and of its component disaccharide moieties α -L-Fuc-(1→2)-β -D-Gal-1-OMe (3) and β -D-Gal-(1→3)-β- D-GalNAc-1-OPr (4) was investigated with the aid of molecular-mechanics energy minimizations and molecular-dynamics simulations. These calculations suggested the occurrence of two conformations for each compound characterized by different φ and Ψ glycosidic angles. However, 1H-NMR investigation of D2O solutions of 2-4 indicated a sure preference for one of the two conformers with a contribution of the other one ranging from negligible to low.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19940770310
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  • 82
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    Synthesis of a New Bivalent Hirudin Analog (hirufos), which includes a stable 4′-phosphono-L-phenylalanine mimic of (L-tyrosine O4-sulfate)-63 (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 679-684 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis on solid phase of a new derivative of the anticoagulant protein hirudin is described (see Scheme and Fig.1, I). The henicosapeptide is a bivalent conjugate of the C-terminus of hirudin and of the active-site-binding tetrapeptide D-Phe-Pro-Arg-Pro linked via a tetraglycine spacer. The peptide, for which the name hirufos was coined, incorporates a stable phosphono derivative of L-phenylalanine which, combined with the other structural modifications, leads to a potent anticoagulant agent. Synthesis was readily achieved by the (9H-fluoren-9-yl)-methoxycarbonyl (Fmoc) strategy followed by acidolytic cleavage from the resin and deprotection, including the liberation of the crucial phosphonic group on L-phenylalanine.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19940770311
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  • 83
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    Organic Reactions in the Solid State: The reactivity of guest molecules in tri-o-thymotide clathrates (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 691-708 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tri-o-thymotide (TOT) clathrates are enantiomorphous and enantioselective (chiral cages). It was shown that an external molecular reactant can diffuse into the TOT host crystal lattice and reacts with the included molecule (guest) in characteristic ways, differing from those occurring in liquid solutions. Several aspects of the action of hydrogen halides (HCl, HBr) on the chemical behavior of included oxiranes were investigated for solid-gas and solid-liquid (aqueous) systems. Under well established experimental conditions, these reactions gave regiospecifically one target product and were asymmetric. The included substrate underwent first an acid-catalyzed allylic isomerization that is cage-specific and mostly quantitative. In sheer contrast, strong basic conditions were required to promote, in reduced yield, the analogous transformation in solution. The regiospecificity and enantioselectivity of several intra-crystalline conversions allowed the accurate determination of the absolute configuration of several guest molecules. Kinetic measurements were achieved that disclosed some striking features of this new type of heterogeneous reactions. Tentative models for the cage stereoselective mechanisms are briefly discussed.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19940770313
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  • 84
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    1:1 Metal Complexes of Bivalent Cobalt, Nickel, Copper, Zink, and Cadmium with the Tripodal Ligand tris[2-(dimethylamino)ethyl]amine: Their stabilities and the X-ray crystal structure of its copper(II) complex sulfate (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 685-690 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The complex formation by Co2+, Ni2+, Cu2+, Zn2+, and Cd2+ with tris[2-(dimethylamino)ethyl]amine (N(CH2CH2NMe2)3, Me6tren) was investigated at 25° and at an ionic strength of 1, using VIS spectroscopy and potentiometric measurements. The stability constants of these complexes are compared with those of tris(2-aminoethyl)amine (N(CH2CH2NH2)3, tren), obtained under the same conditions. The values of the constants for Me6tren are much lower than those for tren, due to the bulky Me substituents. The values of the constants can be correlated with the ability of the individual metal ions to adopt coordination number 5. This appears to be easier for Cu2+ and Co2+ than for Cd2+ and Zn2+ and is very difficult for Ni2+. The 1:1 complexes [ML(H2O)]2+ are monoprotonic acids whose pKs values are similar or lower than those of the corresponding aquametal ions. The X-ray crystal structure of the copper(II) complex [Cu(SO4)(Me6tren)] · 8H2O reveals pentacoordination at the central ion. The UV/VIS spectra of the aqueous solutions of the Co2+, Ni2+, and Cu2+ 1:1 complexes confirm that the same coordination number is present also in these complexes.
    Additional Material: 5 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19940770312
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  • 85
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    The Revised Structure of the Norditerpenoid Alkaloid Peregrine (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1768-1772 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structure of peregrine (1), a norditerpenoid alkaloid isolated from Delphinium peregrinum var. elongatum BOISS., was revised on the basis of the 1H-COSY, HMQC, HMBC, and ROESY NMR spectra and of the X-ray analysis of its parent alcohol 2. Some of the 13C-NMR resonances of 1 and the related alkaloids peregrine alcohol (2), 14-O-acetylperegrine (3), bicoloridine (4), bicoloridine alcohol (5), 6-O-acetylbicolorine (6), bicolorine (7), and 14-O-acetylbicolorine (8), were also reassigned.
    Additional Material: 4 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19940770708
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  • 86
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    Nucleotides. Part XLIVPart XLIII: [1].. Synthesis, characterization, and biological activity of monomeric and trimeric cordycepin-cholesterol conjugates and inhibition of HIV-1 replication (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1757-1767 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The antivirally active 3′-deoxyadenylyl-(2′-5′)-3′-deoxyadenylyl-(2′-5′)-3′-deoxyadenosine (cordycepin trimer core) was modified at the 2′- or 5′-terminus, by attachment of cholesterol via a carbonate bond (→ 15) or a succinate linker (→ 16 and 27) to improve cell permeability. The corresponding monomeric conjugates 4, 7, and 21 of cordycepin were prepared as model substances to study the applicability of the anticipated protecting groups - the monomethoxytrityl (MeOTr), the (tert-butyl)dimethylsilyl (tbds), and the β -eliminating 2-(4-nitrophenyl)ethyl (npe) and 2-(4-nitrophenyl)ethoxycarbonyl (npeoc) groups - for the final deblocking steps without harming the ester bonds of the conjugate trimers. The syntheses were performed in solution using phosphoramidite chemistry. The fully protected trimer conjugates 13, 14, and 26 as well as all intermediates were characterized by elemental analyses, UV and 1H-NMR spectra. The deblocked conjugates 15, 16, and 27 were pure according to HPLC and showed the correct compositions by mass spectra. Comparative biological studies indicated that cordycepincholesterol conjugate trimers 16 and 27 were 333- and 1000-fold, respectively, more potent inhibitors of HIV-1-induced syncytia formation than cordycepin trimer core.
    Additional Material: 1 Tab.
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  • 87
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    Metal-Ion-Coordinating Properties of a Viral Inhibitor, a pyrophosphate analogue, and a herbicide metabolite, a glycinate analogue: The solution properties of the potentially five-membered chelates derived from phosphonoformic acid and (aminomethyl)phosphonic acid (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1738-1756 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrophosphoric-acid-analogue phosphonoformic acid (pfa) and the amino-acid-analogue (aminomethyl)phosphonic acid (ampa) both form, in the deprotonated state, i.e., as -OOC-PO32- and H2N—CH2—PO32-, respectively, five-membered chelate rings with metal ions. pfa inhibits both phosphate transport and virus replication, while ampa is a metabolic product of the common herbicide glyphosate ( = N-(phosphonomethyl)glycine). The acidity constants of H2pfa- and H2ampa± as well as the stability constants of the [M(Hpfa)], [M(pfa)]-, [M(Hampa)]+, and [M(ampa)] complexes, where M2+ = Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Cu(2,2′-bipyridyl)2+, Cu(1,10-phenanthroline)2+, Zn2+, or Cd2+, have been determined by potentiometric pH titrations in aqueous solution at 25° and I = 0.1M (NaNO3). The structures of isomeric complexes and the connected intramolecular equilibria are deduced and evaluated based on the equilibrium constants measured and those calculated via the pKa values of the above mentioned ligands and previously established log K vs. pKa straight-line plots (H. Sigel et al., Helv. Chim. Acta 1992, 75, 2634) for a simple phosphonate-M2+ coordination. pfa forms stronger complexes than ampa with all the above mentioned metal ions, with the single exception of [Cu(ampa)] which is slightly more stable than [Cu(pfa)]-. In neutral solutions, more precisely at pH of ca. 6, pfa complexes of alkaline-earth-metal ions retain one phosphonate-bound proton, [M(Hpfa)], while those of the transition-metal ions chelate with the trianionic ligand, pfa3-. In accord with increasing ligand-basicity, the stability-constant order for all metal-ion complexes is oxalate 〉 pfa 〉 pyrophosphate but, owing to proton competition in pyrophosphate, in neutral solutions metal-ion complexation of pfa3- competes with P2O74-. With ampa alkaline-earth-metal ions interact only with the phosphonate group of even the dianionic ligand (though Mg2+ appears to form a low fraction of a [Mg(ampa)] chelate) while transition-metal ions form chelates which are comparable in stability to those of glycinate.
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  • 88
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    X-Ray Crystal Structure of the 2-Phenyladamant-2-yl Cation (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1773-1780 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The crystal structure of the Sb2F11 salt of the 2-phenyladamant-2-yl cation, 1 · Sb2F11, was determined at 183 K (P21/c, R1 = 0.0652, σ(C—C) = 0.02 Å), because earlier published results indicated a charge delocalization from the cationic C(2) into the σ framework (C—C hyperconjugation) and a bending of the C(2) bridge. In the structure of 1, a displacement of the C(2) bridge by 7.8(12)° from the symmetrical position and C—C bond-length deviations from expectation values were found which are in agreement with preferential C—C hyperconjugation on one face of C(2). The interactions of 1 with two Sb2F11 counterions nearest to C(2) also indicate different behaviour of the two faces of C(2). The benzylic resonance in 1 is confirmed.
    Additional Material: 5 Ill.
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  • 89
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    Facile Preparation of (±)-12-Epiprostaglandins from 7-Oxabicyclo[2.2.1]hept-5-en-2-one via an all-cis-formyllactone related to Corey lactoneA preliminary communication of one part of this work was published [1]. (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1781-1790 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bicyclic monoselenoacetal 7, easily obtained from (±)-7-oxabicyclo[2.2.1]hept-5-en-2-one (6) via a radical addition-acyl migration sequence, was converted to racemic 12-epiprostaglandins 3 and 4. The key intermediate was the all-cis-formyllactone 2b related to Corey lactone (see 12; Scheme 1). The presence of a (tert-butyl)-dimethylsilyl protective group for the 11-OH substituent (prostaglandin numbering) was found to be crucial in avoidingβ -elimination and epimerization during the Wittig-Horner reaction (Scheme 2). Epimerization at C(12) at the formyllactone stage (see 2b) was also possible and gave the known precursor 1b of naturally occurring prostaglandins and analogs.
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  • 90
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    Stability of Charge-Transfer Complexes of CS2 with PH3 and its derivatives: Ab initio MRSDCI/CASSCF StudyDedicated to Prof. Jan Linderberg, an excellent theoretician and marvelous friend, on the occasion of his 60th birthday (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1810-1816 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: While trialkylamines and dialkyl(phenyl)amines do not react with CS2 in the sense of an addition reaction, the analogous phosphines react smoothly. Attempts to interpret the reaction course on the basis of semiempirical, HF, MP2, and MP4 calculations of energy changes failed completely. To understand why Me3P or Me2PhP react so vigorously (liquid phase, 300 K) with CS2, CASSCF and MRSDCI calculations must be carried out.
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    URL: http://dx.doi.org/10.1002/hlca.19940770712
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  • 91
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    Synthesis and Complexation Properties of a New Class of Receptors based on a cone-configurated tetra-p-(tert-butyl)calix[4]arene and bipyridyl subunits (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1817-1825 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 0The bipyridyl-armed tetra-p-(tert-butyl)calix[4]arenes 1-5 were synthesized from tetra-p-(tert-butyl)-calix[4]arene A and 6-(bromomethyl)-6′-methyl-2,2′-bipyridine (B) by direct base-strength-driven regioselective O-alkylation or by stepwise procedures. Preliminary complexation studies of the ligands 1-3 with CuI affording the complexes 6-8 are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770713
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    A Kinetic Analysis of the Reaction Catalysed by (Hydroxymethyl)bilane SynthaseAbbreviations used: FPLC, fast-protein liquid chromatography; HMBS, (hydroxymethyl)bilane synthase; MAD, multiwavelength anomalous diffraction: PBG, porphobilinogen: SeMet, selenomethionine. (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1791-1809 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (Hydroxymethyl)bilane synthase (HMBS) catalyses the conversion of porphobilinogen (2) into the (hydroxymethyl)bilane derivative 3, a linear tetrapyrrolic intermediate in the biosynthesis of haem, chlorophyll, and related pigments. The conversion involves the sequential formation of four intermediate covalent enzyme-substrate complexes, before the product is released. We analysed the pre-steady-state kinetics of the formation of the complexes, taking advantage of their remarkable chemical stability allowing chromatographic separation. The experimental approach involved the generation of the complexes while HMBS was immobilised on an anion-exchange column. A solution being 0.2 Km in substrate was pumped through the column during a time interval which was varied to sample the pre-steady-state period. Then, the enzyme and enzyme-substrate complexes were eluted and their proportions evaluated. A computer simulation of the pre-steady-state time course, in combination with a χ2 fitting to the experimental data, allowed the specificity constants kcat/Km for the individual steps of the process to be derived. By repeating the analysis with variants of HMBS in which specific amino acids were replaced by others, we demonstrated that it is possible to trace the consequences of amino-acid replacements down to the individual steps of the reaction sequence. Since the positions of the amino acids concerned in the three-dimensional structure were known, detailed structure-function relationships become evident in this way.
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    URL: http://dx.doi.org/10.1002/hlca.19940770711
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  • 93
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    Preparation and Structure of Oligolides from (R)-3-Hydroxypentanoic Acid and comparison with the hydroxybutanoic-acid derivatives: A small change with large consequencesPart of the projected Ph.D. theses of T.H., F.N.M.K., and U.D.L., ETH-Zürich. (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 2007-2034 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cyclic oligomers of (R)-3-hydroxyvaleric acid (3-HV) are prepared from the monomer by three different methods, giving various ratios of the oligomers. The macrocycles containing three to twelve 3-HV units (12- to 48-membered rings) are isolated in pure form by chromatography. The triolide 3 can be separated by distillation and isolated on large scale. Biopol, the copolymer of (R)-3-hydroxybutanoic acid (3-HB) and (R)-3-hydroxyvaleric acid (3-HV), is degraded to mixtures of Me- and Et-substituted triolides (‘mixolides’) with high crystallization tendency. The X-ray crystal structures of the tetrolide 4, pentolide 5, hexolide 6, heptolide 7, and of two ‘mixolides’ (with inclusions of solvent) have been determined (Figs. 3-7, 10, and 11) and are compared with those of the corresponding 3-HB derivatives reported previously. From the structural data, a 31 and a 21 helix of 3-HV can be modelled, and the latter one compared with helix structures of P9(3-HB) and P(3-HV) derived from stretch-fibre X-ray scattering. Crystals of a water-containing NaSCN complex of the triethyl triolide 3 were obtained in good quality for X-ray analysis. The structure (Figs. 12, 13, and Table 6) contains an interesting array of C=O and H2O O-atoms around the Na+ ions along a channel-type tube (a-axis of the crystal) which may be relevant to the role of P(3-HB) and P(3-HV) as components of cellular ion channels.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770727
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  • 94
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    Synthesis of Tri-, Penta-, and Heptapeptides Containing and (R)-2-alkyl-2-amino-3-(methylamino)-propionic acid residue in the central positionThis project was supported by the Swiss National Science Foundation, project No. 20-30770.91 (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 2035-2050 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: By conventional peptide-coupling methods (C to N direction; mixed anhydride, bis(2)-oxooxazolidin-3-yl)phosphinoyl chloride (Bop-Cl), or dicyclohexylcarbodiimide (DCC), 2-amino-2-methyl-3-(methylamino)-propionic acid and 2-amino-2-ethyl-3-(methylamino)propionic acid ( = 2-amino-2-[(methylamino)methyl]butanoic acid) are incorporated in the central position of tri-, penta-, and heptapeptides (see 3-7, 21, and 22). The fragment coupling of the β -amino group of the diamino-acid moiety in a tetrapeptide led to partial epimerization, and thus, two epimeric heptapeptide derivatives were actually obtained (7 and epi-7). The final deprotection to the free heptapeptide (involving a Me3SiI cleavage of BocNH and MeOCONH, a saponification with NaOH, and HPLC purification) gave both the desired product (isopeptide 21), with the β -amino group inside the peptide backbone, and a product (peptide 22) of transpeptidation, with the α-amino group of the diamino acid incorporated and a (methylamino)methyl group as the side chain. Peptide 22 is completely converted to the isopeptide 21 by prolonged treatment with base. The heptapeptide 21 was analyzed by elaborate 2QF-COSY and NOESY NMR measurements in H2O/CD3OD at -5° (Table, Fig.); there is no indication for β -sheet or helical structures, a fact which was also confirmed by CD measurements.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19940770728
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  • 95
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    Masthead (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770801
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  • 96
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    Mitteilungen - Communications (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 2070-2070 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770731
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  • 97
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    Preparation and Transmetallation of a Triphenylstannyl β-D-Glucopyranoside: A highly stereoselective route to β-D-C-glycosides via glycosyl dianions (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 2060-2069 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The triphenylstannyl β-D-glucopyranoside 4 was synthesized in one step from the 1,2-anhydro-α-D-glucopyranose 3 with (triphenylstannyl)lithium (Scheme 1). Transmetallation of 4 with excess BuLi, followed by quenching the dianion 7 with CD3OD gave (1S)-1,5-anhydro-3,4,6-tri-O-benzyl-[1-2H]-D- glucitol (8) in 81% yield (Scheme 2). Trapping of 7 with benzaldehyde, isobutyraldehyde, or acroleine gave the expected β-D-configurated products 11, 12, and 13 in good yields. Preparation of C-acyl glycosides from acid chlorides, such as acetyl or benzoyl chloride was not practicable, but addition of benzonitrile to 7 yielded 84% of the benzoylated product 14. Treatment of 7 with MeI led to 15 (30%) along with 40% of 18, C-alkylation being accompanied by halogen-metal exchange. Prior addition of lithium 2-thienylcyanocuprate increased the yield of 15 to 50% and using dimethyl sulfate instead of MeI led to 77% of 15. No α-D-anomers could be detected, except with allyl bromide as the electrophile, which yielded in a 1:1 mixture of the anomers 16 and 17.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770730
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  • 98
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    C2-Symmetric Bicyclic Diols as Chiral Ligands in the titanate-catalyzed enantioselective addition of alkylzinc reagents to aldehydes (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 2111-2116 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Enantiomerically pure C2-symmetric 1,4-diols embodying bicyclic C-frameworks were synthesized by means of asymmetric carbo-Diels-Alder reactions as key steps (Scheme 1). They were investigated as chiral ligands in the enantioselective addition of ZnEt2 to aromatic aldehydes. In the presence of 20-40 mol-% of the titanates formed from these diols and [Ti(i-PrO)4] at -78°, the respective 1-arylpropanols were obtained with enantiomer ratios up to 93:7 (Scheme 2, Table).
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770803
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  • 99
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    Synthesis of Aristotelia-Type Alkaloids. Part XIIIPart XIII, see [1].. Total syntheses of (+)-makonine, (+)-aristotelinone, and (+)-11,12-didehydroaristoteline (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 2125-2132 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The oxidative transformation of synthetic (+)-aristoteline ((+)-6) into other metabolites which had been isolated from Aristotelia species was investigated. Thus, treatment of (+)-6 with I2 as the single oxidant furnished the naturally occurring indole alkaloids (+)-makonine ((+)-9),(+)-aristotelinone ((+)-11), or (+)-11, 12-didehydroaristoteline ((+)-7) in good yields, the selectivity of the oxidation process depending on the chosen reaction conditions.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770805
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  • 100
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    Preparation and Structural Analysis of Several New α,α,α′,α′-Tetraaryl-1,3-dioxolane-4,5-dimethanols (TADDOL's) and TADDOL analogs, their evaluation as titanium ligands in the enantioselective addition of methyltitanium and diethylzinc reagents to benzaldehyde, and refinement of the mechanistic hypothesis (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 2071-2110 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Preparation and screening of twenty new ligands, all analogs of α,α,α′,α′-tetraaryl-1,3-dioxolane-4,5-dimethanol (TADDOL), for the Ti-catalyzed asymmetric addition of methyltri(isopropoxy)titanium and diethylzinc to benzaldehyde are described. These ligands have the dioxolane ring of the TADDOL's replaced by cyclobutane, cyclopentane, cyclohexene, cyclohexane, bicyclo[2.2.1]heptene and -heptane and bicyclo[2.2.2]octene and -octane moieties; several have H-atoms or alkyl groups in place of the aryl groups, and nine of them have C2 symmetry. X-Ray crystallography and molecular mechanics are used to analyze the structure of the ligands, and two structural features appear to correlate with selectivity: (i) the torsion angle for the chelating O-atom and the ortho-C-atom of the axial Ph group (a small, ca. 19°, angle is optimum, Fig.8) and (ii) the “degree of perpendicularity” of the axial Ph group (Fig. 9). Competition experiments indicate that TADDOL 1a catalyzes both the methyltitanium and diethylzinc additions ≥ 50 times faster than the related dioxolane analogs 12a, 12c, and 12e (Scheme 7), indicating that both axial and equatorial aryl groups (see Footnote 6) are necessary for ligand-accelerated catalysis of these reactions. A refined mechanistic hypothesis is presented (Fig. 10) to explain the selectivities observed for these new ligands. Our analysis suggests that a combination of structural features appear necessary for good catalytic efficiency and high selectivity. These features, especially the rather subtle conformational effects, appear to be optimized (among the ligands tested) in the TADDOL's.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19940770802
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