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  • Springer  (109)
  • 2020-2022  (48)
  • 2000-2004  (42)
  • 1975-1979  (19)
  • 1955-1959
  • 1
    Electronic Resource
    Electronic Resource
    Studies on the synthesis of β-keto esters derived from dipeptides: search for a low-epimerizing method (2000)
    Springer
    International journal of peptide research and therapeutics 7 (2000), S. 143-149 
    Details
    ISSN: 1573-3904
    Keywords: dipeptide analogues ; epimerization ; imidazolide-derived dipeptides ; keto esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary β-Keto esters derived from dipeptides are prepared by application of common methodologies employed for the synthesis of amino acid-derived β-keto esters; however, epimerization of the C-terminal residue occurred to different extents depending on the method. In imidazolide activated dipeptides, this epimerization is due to the CDI activation step and to the configurational instability of the intermediate imidazolides in different reaction media. Regarding yield and diastereomeric purity, the method of choice proved to be the reaction of dipeptide-derived imidazolide with the potassium salt of malonic half esters in the presence of MgCl2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02443581
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  • 2
    Electronic Resource
    Electronic Resource
    Studies on the synthesis of β-keto esters derived from dipeptides: search for a low-epimerizing method (2000)
    Springer
    International journal of peptide research and therapeutics 7 (2000), S. 143-149 
    Details
    ISSN: 1573-3904
    Keywords: dipeptide analogues ; epimerization ; imidazolide-derived dipeptides ; keto esters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract β-Keto esters derived from dipeptides areprepared by application of common methodologiesemployed for the synthesis of amino acid-derivedβ-keto esters; however, epimerization of theC-terminal residue occurred to different extentsdepending on the method. In imidazolide activateddipeptides, this epimerization is due to the CDIactivation step and to the configurational instabilityof the intermediate imidazolides in different reactionmedia. Regarding yield and diastereomeric purity, themethod of choice proved to be the reaction ofdipeptide-derived imidazolide with the potassium saltof malonic half esters in the presence of MgCl2.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008996908844
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  • 3
    Electronic Resource
    Electronic Resource
    Thermodynamics of copper(II) dicarboxylate coordination in aqueous solution (1978)
    Springer
    Transition metal chemistry 3 (1978), S. 147-152 
    Details
    ISSN: 1572-901X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The association of H+ and Cu2+ with malonate, maleate, succinate and phthalate ions has been investigated both potentiometrically and calorimetrically at 25° and I = 0.1 mol dm−3 (NaClO4). The structures of the complexes existing in aqueous solution are proposed on the basis of thermodynamic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01393532
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  • 4
    Electronic Resource
    Electronic Resource
    Symbiotic efficiency and infectivity of an autochthonous arbuscular mycorrhizal Glomus sp. from saline soils and Glomus deserticola under salinity (2000)
    Springer
    Mycorrhiza 10 (2000), S. 137-143 
    Details
    ISSN: 1432-1890
    Keywords: Keywords Arbuscular-mycorrhiza ; Infectivity ; Fungal isolate ; Salt stress ; Symbiotic efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The purpose of this study was to compare the effect of salinity on the symbiotic efficiencies and mycelial infectivity of two arbuscular mycorrhizal fungi (AMF), one isolated from saline soils (Glomus sp.) and the other (Glomus deserticola) from nonsaline soils (belonging to the Estación Experimental del Zaidín collection). Lettuce plants inoculated with either of these two fungi or maintained as uninoculated controls were grown in soil with three salt concentrations (0.25, 0.50 or 0.75 g NaCl kg–1 dry soil). Both AMF protected host plants against salinity. However, when the results of shoot dry weight and nutrient contents were expressed relative to the total length of mycorrhiza formed, it was found that both AMF differed in their symbiotic efficiencies. These differences were more evident at the two highest salt levels. Glomus sp.-colonized plants grew less and accumulated less N and P, whereas they formed a higher amount of mycorrhiza. The mechanism by which Glomus sp. protected plants from the detrimental effects of salt was based on the stimulation of root development, while the effects of G. deserticola were based on improved plant nutrition. The increase in salinity of soil decreased the hyphal growth and/or viability of Glomus sp. to a higher extent than those of G. deserticola since the mycelial network generated by G. deserticola was more infective than that of Glomus sp.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720000075
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  • 5
    Electronic Resource
    Electronic Resource
    Orthophosphate determination: A simple spectrophotometric method for the measurement of the orthophosphate-triethylamine-molybdate complex (1979)
    Springer
    Microchimica acta 72 (1979), S. 181-185 
    Details
    ISSN: 1436-5073
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Triäthylamin ist ein selektives Fällungsreagens für Phosphormolybdänsäure, das die Trennung von Orthophosphat aus Mischungen von Phosphorsäureestern und Anhydriden erlaubt. Eine einfache Methode zur Bestimmung von Orthophosphat-Triäthylamin-Molybdat wurde beschrieben. Sie beruht auf der Messung der Ultraviolett-Absorption des Komplexes. Fünf bis 250 nMol gefälltes Orthophosphat werden in 3 ml Methanol gelöst und die Absorption dieser Lösung gegen Wasser bei 320 nm gemessen. Der molare Extinktionskoeffizient des Komplexes unter diesen Bedingungen ist 2,09·107 1·Mol−1·cm−1.
    Notes: Summary Triethylamine is a selective precipitant for phosphomolybdic acid which allows separation of orthophosphate from phosphoric acid esters and anhydrides. In this paper a simple method for the estimation of the orthophosphate-triethylamine-rnolybdate complex, based on its ultraviolet absorption spectrum, is described. The precipitate, corresponding to a range of 5–250 nmole of orthophosphate, is dissolved in 3 ml of methanol and the absorbance of the solution measured at 320 nm against water. The molar absorptivity of the complex at this wavelength is 2.09 × 1071·mole−1·cm−1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01197370
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  • 6
    Electronic Resource
    Electronic Resource
    Protoplast-like structures formation from two species of enterobacteriaceae by fosfomycin treatment (1978)
    Springer
    Archives of microbiology 118 (1978), S. 219-221 
    Details
    ISSN: 1432-072X
    Keywords: Protoplasts ; Fosfomycin ; Escherichia coli ; Serratia marcescens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A procedure for protoplasts formation from Escherichia coli and Serratia marcescens by treatment with fosfomycin alone is described. This method gives high and low yields of stable protoplasts from E. coli and S. marcescens respectively. In the last case numerous spheroplasts were obtained. Electron micrographs of intact cells, protoplasts and spheroplasts are shown.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00415732
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  • 7
    Electronic Resource
    Electronic Resource
    Thermodynamics of 2,2′,2′'-terpyridinecopper(II) complexes in aqueous solution (1979)
    Springer
    Transition metal chemistry 4 (1979), S. 328-332 
    Details
    ISSN: 1572-901X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary The thermodynamic quantities relative to the protonation and the complexation of 2,2′,2′'-terpyridine with copper(II) ion have been determined at 25° and I=0.1 mol dm−3 (NaNO3). The ΔG∘ data was obtained by potentiometric measurements; a copper selective electrode was employed for the study of the complexation equilibria. The ΔH∘ values have been determined by direct calorimetry. The hydrolytic species, existing at pH〉6 and their relative ΔG∘ and ΔH∘ values have also been obtained. From the thermodynamic data the importance of enthalpy and entropy terms in stabilizing the complexes is assessed. Moreover some considerations on the chelating effect are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00618328
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  • 8
    Electronic Resource
    Electronic Resource
    Determination of intermediary metabolites in yeast. Critical examination of the effect of sampling conditions and recommendations for obtaining true levels (1976)
    Springer
    Molecular and cellular biochemistry 13 (1976), S. 73-78 
    Details
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary The effect of sampling conditions on the levels of adenine nucleotides, pyridine nucleotides, glycolytic intermediates and related metabolites in yeast has been studied. A systematic examination of the conditions for harvesting has shown that it can be best accomplished by rapid filtration. Delays in the handling for removal of the medium, as is usual in the process of obtaining a number of data reported in the literature, lead to important changes in some of the metabolites examined. It is also shown that when a washing is imperative it can be carried out with a methanol-water mixture (50/50, v/v) cooled at −40° without loss of intracellular concentrations of non-readily diffusible metabolites. On the basis of this experience the outline of a generally applicable procedure is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01837056
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  • 9
    Electronic Resource
    Electronic Resource
    Effectors of glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase of rat liver. (1977)
    Springer
    Molecular and cellular biochemistry 17 (1977), S. 147-149 
    Details
    ISSN: 1573-4919
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Summary The lower Vmax of 6PGDH with respect to G6PDH and its higher sensitivity to inhibition by NADPH, suggest the existence of an imbalance between the two dehydrogenases of the pentose phosphate pathway in rat liver. Possible modulators of these activities, particularly in relation with the inhibition by NADPH in physiological conditions, have been investigated. The results suggest that in both cases the inhibition by NADPH is strictly isosteric and that the relative affinities for the reduced and oxidized forms of the pyridine nucleotide are unaffected by glutathion, the intermediates of the pentose phosphate shunt or some divalent ions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01730834
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  • 10
    Electronic Resource
    Electronic Resource
    Three maize root-specific genes are not correctly expressed in regenerated caps in the absence of the quiescent center (2000)
    Springer
    Planta 211 (2000), S. 23-33 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Development (root cap) – Quiescent center – Root cap initials –Zea (root development)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. The quiescent center is viewed as an architectural template in the root apical meristem of all angiosperm and gymnosperm root tips. In roots of Arabidopsis thaliana (L.) Heynh., the quiescent center inhibits differentiation of contacting initial cells and maintains the surrounding initial cells as stem cells. Here, the role of the quiescent center in the development of the maize (Zea mays L.) root cap has been further explored. Three maize root-specific genes were identified. Two of these were exclusively expressed in the root cap and one of them encoded a GDP-mannose-4,6-dehydratase. Most likely these two genes are structural, tissue-specific markers of the cap. The third gene, a putative glycine-rich cell wall protein, was expressed in the cap and in the root epidermis and, conceivably is a positional marker of the cap. Microsurgical and molecular data indicate that the quiescent center and cap initials may regulate the positional and structural expression of these genes in the cap and thereby control root cap development.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004250000276
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