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  • 1
    Electronic Resource
    Electronic Resource
    Plant competition for light analyzed with a multispecies canopy model (1990)
    Springer
    Oecologia 82 (1990), S. 374-380 
    Details
    ISSN: 1432-1939
    Keywords: Triticum aestirum ; Avena fatua ; Canopy photosynthesis ; Canopy model ; Light competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The importance of photosynthetic characteristics such as quantum efficiency or carboxylation efficiency for carbon gain of plants competing for light in dense stands is dependent on several environmental factors and structural features of the canopy. A quantitative analysis of photosynthesis of competing plants in mixed stands of wheat and wild oat (Avena fatua L.), a common weed of wheat, involved measuring photosynthetic parameters of individual leaves at different heights in the canopy throughout the growing season. This information combined with detailed assessments of canopy structure was used with a multispecies canopy model to evaluate the importance of different photosynthetic characteristics for carbon gain in this canopy environment. Independent photosynthesis data sets were used to validate predictions of the model. Carboxylation efficiency (CE) and CO2-and light-saturated photosynthetic capacity (AML) were highly correlated and decreased with depth in the canopy for both species. Quantum efficiency (α) did not tend to decrease with depth in the canopy. Sensitivity analyses with the model for whole-plant carbon gain of each species over entire day periods were conducted. These showed that changes in CE and AML had an influence similar to that of changes in α on carbon gain for both species. This was not necessarily expected from single-leaf photosynthetic behavior in response to changes in CE, AML and α. The influence of α is more pronounced in the lower, more shaded portions of the canopy than are changes in CE and AML. Appreciable differences between the species were apparent for carbon gain under different weather conditions. The differences between the species in carbon gain when in competition for light were associated more with structural features rather than with photosynthetic characteristics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00317486
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  • 2
    Electronic Resource
    Electronic Resource
    Plant competition for light analyzed with a multispecies canopy model (1990)
    Springer
    Oecologia 82 (1990), S. 560-566 
    Details
    ISSN: 1432-1939
    Keywords: Canopy structure ; Competition for light ; Leaf area index-LAI ; Leaf inclination ; Canopy photosynthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A multispecies canopy photosynthesis simulation model was used to examine the importance of canopy structure in influencing light interception and carbon gain in mixed and pure stands of wheat (Triticum aestivum L.) and wild oat (Avena fatua L.), a common weedy competitor of wheat. In the mixtures, the fraction of the simulated canopy photosynthesis contributed by wheat was found to decline during the growing season and this decline was closely related to reductions in the amount of leaf area in upper canopy layers. For both species in mixture and in monoculture, simulated photosynthesis was greatest in the middle or upper-middle canopy layers and sensitivity analyses revealed that canopy photosynthesis was most sensitive to changes in leaf area and leaf inclination in these layers. Changes in LAI and leaf inclination affected canopy carbon gain differently for mixtures and monocultures, but the responses were not the same for the two species. Results from simulations where the structural characteristics of the two species were substituted indicated that species differences in leaf inclination, sheath area and the fraction of leaf area alive were of minor consequence compared with the differences in total leaf area in influencing relative canopy carbon gain in mixtures. Competition for light in these species mixtures appears to be influenced most by differences in the positioning of leaf area in upper canopy layers which determines, to a great extent, the amount of light intercepted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00319801
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  • 3
    Electronic Resource
    Electronic Resource
    Formation of glycine conjugate and (-)-(R)-enantiomer from (+)-(S)-2-phenylpropionic acid suggesting the formation of the coa thioester intermediate of (+)-(S)-enantiomer in dogs (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 342-348 
    Details
    ISSN: 0899-0042
    Keywords: arylpropionic acid ; 2-phenylpropionic acid ; glycine conjugation ; stereoselectivity ; chiral inversion ; reverse chiral inversion ; glycine N-acyl transferase ; dog hepatocytes ; chiral HPLC ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It has been proposed that the chiral inversion of the 2-arylpropionic acids is due to the stereospecific formation of the (-)-R-profenyl-CoA thioesters which are putative intermediates in the inversion. Accordingly, amino acid conjugation, for which the CoA thioesters are obligate intermediates, should be restricted to those optical forms which give rise to the (-)-R-profenyl-CoA, i.e., the racemates and the (-)-(R)-isomers. We have examined this problem in dogs with respect to 2-phenylpropionic acid(2-PPA). Regardless of the optical configuration of 2-phenylpropionic acid administered, the glycine conjugate was the major urinary metabolite and this was shown to be exclusively the (+)-(S)-enantiomer by chiral HPLC. Both (-)-(R)- and (+)-(S)-2-phenylpropionic acid were present in plasma after the administration of either antipode, and further evidence of the chiral inversion of both enantiomers was provided by the presence of some 25% of the opposite enantiomer in the free 2-phenylpropionic acid and its glucuronide excreted in urine after administration of (-)-(R)- and (+)-(S)-2-phenylpropionic acid. The (+)-(S)-enantiomer underwent chiral inversion to the (-)-(R)-antipode when incubated with dog hepatocytes. These data suggests that both enantiomers of 2-phenylpropionic acid are substrates for canine hepatic acyl CoA ligase(s) and thus undergo chiral inversion, but that the CoA thioester of only (+)-(S)-2-phenylpropionic acid is a substrate for the glycine N-acyl transferase. These studies are presently being extended to the structure and species specificity of the reverse inversion and amino acid conjugation of profen NSAIDs. © 1992 Wiley-Liss, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040603
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  • 4
    Electronic Resource
    Electronic Resource
    Stereoselectivity of the aliphatic hydroxylation of 6-n-propylchromone-2-carboxylic acid in rat and guinea pig (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. 191-198 
    Details
    ISSN: 0899-0042
    Keywords: stereoselectivity ; regioselectivity ; aliphatic hydroxylation ; rat ; guinea pig ; 6-n-propylchromone-2-carboxylic acid ; Mosher's esters ; 1H-NMR configurational assignment ; 19F-NMR configurational assignment ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Following administration of 6-n-propylchromone-2-carboxylic acid (6-n-PCCA) (500 μmol/kg) to male rats, three metabolic products were detected and isolated from the 0-24 h urine. All were identified as resulting from oxidation exclusively along the 6-n-propyl moiety. Some 66% of the dose was excreted in the 0-24 h urine, 55% of which was 6-PCCA, with 15% as (6-1′-hydroxypropyl)chromone-2-carboxylic acid (6-1′-HPCCA), 22% as 6-(2′-hydroxypropyl)chromone-2-carboxylic acid (6-2′-HPCCA), and 4% as (6-3′-carboxypropyl)chromone-2-carboxylic acid (6-3′-CPCCA). Derivatization of the methyl esters of the hydroxylated metabolities with S-α-methoxy-α-(trifuloromethyl)-phenylacetyl chloride (Mosher's reagent) allowed the evaluation of urinary enantiomeric composition by HPLC and assignment of their absolute configurations by NMR. This was found to be 90:10 (R/S) for 6-2′-HPCCA, and 7:93 (R/S) for 6-1′-HPCCA. When rats were dosed with the racemic 1′- and 2-hydroxy metabolites; no stereoselective metabolism or excretion was observed. Administration of 6-n-PCCA to male guinea pigs revealed that this species was unable to metabolise this compound. © 1993 Wiley-Liss, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530050316
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  • 5
    Electronic Resource
    Electronic Resource
    Editorial: Note from the European editor (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 5 (1993), S. iv 
    Details
    ISSN: 0899-0042
    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/chir.530050502
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  • 6
    Electronic Resource
    Electronic Resource
    Lack of stereoselectivity of the peroxisome proliferation induced by 2-phenylpropionic acid: Evidence against a role for lipid disturbance in peroxisome proliferation (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 6 (1994), S. 365-371 
    Details
    ISSN: 0899-0042
    Keywords: 2-phenylpropionic acid ; peroxisome proliferation ; rat liver ; acyl CoA ; stereoselectivity ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The significance of disturbances of lipid metabolism caused by xenobiotic acyl-CoAs as possible causes of peroxisomal proliferation has been studied with the enantiomers of 2-phenylpropionic acid (2-PPA), the (R)-enantiomer of which is converted to the acyl-CoA in rats while its (S)-antipode is not. rac-2-PPA (250 mg/kg/day ip × 3) was shown to be an hepatic peroxisomal proliferator in male Sprague-Dawley rats on the basis of increases in microsomal cytochrome P-450 content and lauric acid hydroxylation and hepatic CN--insensitive palmitoyl-CoA oxidation, a peroxisomal marker activity, while electron microscopy revealed a rise in the peroxisome/mitochondria ratio in hepatocytes. Further studies established the dose-response relationships for these biochemical changes. The (R)- and (S)-enantiomers were administered at a dose of 50 mg/kg/day ip × 3 and both were peroxisome proliferators of very similar potency. The effects of 100 mg/kg/day ip × 3 of the racemate, a dose giving ca. 75% of maximal response, were essentially additive of those of 50 mg/kg/day ip × 3 of its two component isomers. The stereoselectivity of acyl-CoA formation from the enantiomers of 2-PPA was confirmed by their differential inhibition of microsomal palmitoyl-CoA synthesis. Taken together, these data indicate that it is very unlikely that the acyl-CoA of 2-PPA plays any role in the peroxisomal proliferation which this compound causes in the rat. © 1994 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530060502
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  • 7
    Electronic Resource
    Electronic Resource
    Stereoselective aliphatic hydroxylation of 6-n-propylchromone-2-carboxylic acid by female Dutch rabbits (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 4 (1992), S. 1-7 
    Details
    ISSN: 0899-0042
    Keywords: product enantioselectivity ; aliphatic hydroxylation ; 6-n-propylchromone carboxylic acid ; chiral HPLC ; chiral shift 1H-NMR ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 6-n-Alkylchromone-2-carboxylic acids are metabolized solely by aliphatic oxidation. In the rabbit, the 6-n-propyl congener (PCCA) undergoes ω-1 hydroxylation exclusively. Following administration of PCCA to female Dutch rabbits (500 μmol/kg), some 77% of the dose was excreted in the urine, 41% as PCCA and 36% as 6-(2'-hydroxy-n-propyl)chromone-2-carboxylic acid. Since this metabolite is chiral, we have examined the stereochemistry of the excreted material. Diastereoisomeric (as camphanate and α-methoxy-α-(trifluoromethyl)phenylacetate esters) and direct chiral HPLC and chiral lanthanide shift NMR have each shown the S:R ratio of the excreted metabolite to be 76:24. When rabbits were dosed with the racemic metabolite, excretion of the compound was not stereoselective. The regio- and stereo-selectivity of the aliphatic hydroxylation of PCCA are thus reflections of the selectivities of the enzyme systems responsible for its formation and suggest PCCA to be an appropriate probe compound for the study of prochiral-chiral hydroxylations.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530040103
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  • 8
    Electronic Resource
    Electronic Resource
    Regulatory aspects of the development of chiral drugs in Japan: A status report (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 3 (1991), S. 91-93 
    Details
    ISSN: 0899-0042
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/chir.530030202
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  • 9
    Electronic Resource
    Electronic Resource
    Direct determination of cotinine-N-glucuronide in urine using thermospray liquid chromatography/mass spectrometry (1994)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 23 (1994), S. 103-107 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A thermospray liquid chromatographic/mass spectrometric method has been developed for direct determination of cotinine-N-glucurinode in the urine of smokers. Quantification was performed using methyl-d3-cotinine-N-glucuronide as internal standard and monitoring the protonated aglycons. Using a simple preparation, urine samples from four smokers were analyzed and the results compared favorably with those from a previously reported method that quantifies aglycon release following β-glucuronidase treatment. Amounts of cotinine-N-glucuronide found in urine from smokers ranged from less than 0.7 to 21 nmol ml-1, indicating wide inter-individual variability in the metabolic production of this metabolite. Cotinine-N-glucuronide was found to be the second most abundant urinary nicotine metabolite. A similar method was developed for trans-3′-hydroxycotinine-N-glucuronide but this compound was not detected in smokers' urine.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200230210
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of water-soluble polyamidoamines for biomedical applications. II. Polymers possessing intrachain-type secondary amino groups suitable for side-chain attachment (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 50 (1993), S. 393-401 
    Details
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: As part of a program to synthesize water-soluble polymeric carriers suitable for drug binding, the polyaddition reaction of methylenebisacrylamide with comonomers containing two pri-mary amino groups is investigated. The copolymerization of the bisacrylamide with equi-molar quantities of primary diamines under properly controlled experimental conditions is found to proceed in a linear propagation, giving rise to the formation of polyamides comprising two or more secondary amino groups in the recurring unit. Selected diamine monomers include ethylenediamine, diethylenetriamine, triethylenetetramine, 1,2-bis (3-aminopropylamino) ethane, and three 0,0´-bis-(2-aminopropyl) derivatives of poly(ethylene glycol) of different chain length, the last three monomers being chosen because of their outstanding hydrosolubilizing properties. Use of two different diamines in the proper stoi-chiometry leads to corresponding copolymers. The reactions are conducted in aqueous phase over periods of 1-3 days at 65°C, and the polymeric products, possessing the linear polyamidoamine structures 1 and 2, are fractionated by dialysis in membrane tubing with 12000-14000 molecular-mass cutoff and are isolated by freeze-drying as solid or resinous materials possessing complete solubility in water. Inherent viscosities are in the range of 8- 40mLg-1. Microanalytical and spectroscopic data confirm the proposed structures. The suitability of the intrachain secondary amine functions for side chain attachment and drug coupling is demonstrated in model reactions involving N-substitution. © 1993 John Wiley & Sons, Inc.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1993.070500303
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