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  • 1
    Electronic Resource
    Electronic Resource
    Influence of the nuclear and extranuclear substitution on the singlet molecular oxygen [O 2(1Δg)]-mediated photooxidation of tyrosine derivatives: A kinetic study (1995)
    Springer
    Amino acids 8 (1995), S. 367-377 
    Details
    ISSN: 1438-2199
    Keywords: Amino acids ; Tyrosine ; Tyrosine derivatives ; Singlet oxygen ; Photooxidation ; Kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The effect of the substitution pattern on the kinetics of the Type II (O2(1Δg)-mediated) dye-sensitized photooxidation of a series of nine tyrosine derivatives was investigated. Overall (kt) and reactive (kr) rate constants for the interaction of the excited oxygen species with the amino acid derivatives were determined. A parallel study on solvent and pH effects was carried out. The presence of different substituents in nuclear positions or in the amino acid side chain greatly affect the photooxidation rates. An upper limit for photooxidation quantum yield, calculated from the kinetic data, varies from 0.03 to 0.25, being the higher for halogenated tyrosines and the lower for esterified tyrosines and for the nitro-derivative. The variation of solvent polarity and pH of the reaction medium confirm that the presence of the ionized phenolate group in tyrosine, clearly dominates the quenching process. As already postulated for generic phenolic derivatives, it proceeds through a polar intermediate complex which posses some component of charge-transfer character. Esterification of the carboxilic acid of tyrosine selectively decreases the contribution of the reactive step to the overall process of O2(1Δg) quenching. An amide group in the same position does not produce noticiable changes in this sense. The presence of a highly deactivating nitro group in nuclear positions greatly diminishes the magnitude of both overall and reactive interactions. For all three, o-, m- and p-tyrosine the values of photooxidation quantum yields show an excellent parallelism with the rates of consumption of the — NH2 group of the amino acid chain, upon sensitized irradiation. It could react, in the cases of 0- and m-tyrosine in a secondary, non photochemical, step.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00806554
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  • 2
    Electronic Resource
    Electronic Resource
    Considerations on main factors which take part in nitrate contamination of ground water in Spain with relationship to other EU countries (1995)
    Springer
    Nutrient cycling in agroecosystems 43 (1995), S. 203-207 
    Details
    ISSN: 1573-0867
    Keywords: fertilization rates ; manure ; fertirrigation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Analysis of different factors affecting nitrate pollution of waters in Spain and other E.U. countries is presented. Average pluviometry in Spain is ca. 560 l/m2, whereas in the agricultural countries is over 750 l/m2. Fertirrigation in Spain, in drip irrigation, is over 200 M ha. Average rates of mineral fertilization are 36-19-15, in kg/ha N-P2O5-K2O, whereas in the E.U. they are 69-28-30. Animal liquid sludges contribution is in relation to the livestock population and, in Spain, density of bovine and swine heads per ha is 0.8, whereas in the E.U. it is 1.3. Presently situation of underground water pollution in Spain is lower than in the E.U. Northern countries but efforts must be enhanced to improve water quality.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00747703
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    In vitro activity of nonsteroidal antiinflammatory agents, phenotiazines, and antidepressants againstBrucella species (1996)
    Springer
    European journal of clinical microbiology & infectious diseases 15 (1996), S. 418-420 
    Details
    ISSN: 1435-4373
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The in vitro antimicrobial activity of streptomycin, rifampicin, tetracycline, seven nonsteroidal antiinflammatory agents (acetyl-salicylic acid, piroxicam, indomethacin, ibuprofen, ketoprofen, sulindac, and diclofenac), and eight phenotiazine derivatives and antidepressant agents (clorpromazine, fluphenazine, amitryptiline, clomipramine, imipramine, maprotiline, sertraline, and diazepam) against 62 strains ofBrucella spp. was tested. Diclofenac was the most active of the anti-inflammatory agents (MIC90 = 16 μg/ml). The activity of the phenotiazines and antidepressants was heterogeneous, with MIC90S ranging from 16 μg/ml for sertraline and 32 μg/ml for fluphenazine and clomipramine to 〉 512 μg/ml for diazepam. When the six most active anti-inflammatory agents and the six most active psychiatric drugs were tested at pH 5 and pH 4, the MICs remained unchanged except for those of fluphenazine; the MIC50 and MIC90 of this agent increased by one dilution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01690103
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    Paper (German National Licenses)
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