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  • 1
    Electronic Resource
    Electronic Resource
    Kinetic and thermodynamic control of flavylium hydration in the pelargonidin-cinnamic acid complexation. Origin of the extraordinary flower color diversity of Pharbitis nil (1993)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 115 (1993), S. 3125-3132 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00061a011
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Role of transported particulate organic matter in the macroinvertebrate colonization of litter bags in streams (2001)
    Oxford UK : Blackwell Science Ltd
    Freshwater biology 46 (2001), S. 0 
    Details
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. The exposure of mesh litter bags has been widely used to investigate the role of benthic macroinvertebrates in leaf processing in freshwaters. In this sense, several studies have related litter bag breakdown rates to the presence of colonizing invertebrates. A possible confounding factor in such experiments is that the litter bags trap suspended particulate organic matter that can itself attract invertebrate colonists, irrespective of the intended experimental treatment.2. We attempted to quantify the accumulation of particulate organic matter (POM) within litter bags and to investigate its possible impact on macroinvertebrate density and richness. In seven headwater forested streams we exposed mesh bags filled either with beech leaves (Fagus sylvatica) or with plastic strips of an equal surface area.3. Principal component analysis (PCA) showed that bag type and stream were the main explanatory variables for invertebrate colonization and POM accumulation within the bags. In contrast, there was little variation among sampling dates (6.4% of the total inertia).4. The accumulated POM within the bags was substantial (up to 8.83 g ash-free dry mass (AFDM)) but highly variable among sites (mean from 0.32 to 4.58 g AFDM). At each of the seven sites, both richness and abundance of invertebrates were positively correlated with the mass of accumulated POM in bags. Macroinvertebrate colonization (notably taxon richness) was directly linked with the quantity of POM accumulated.5. Our findings provide evidence of a potential pitfall in linking invertebrates to litter processing in mesh bags, particularly when large amounts of POM, entrained in stream flow, accumulate within the bags. An evaluation of the POM mass trapped in litter bags could account for the erratic patterns sometimes observed in their colonization by invertebrates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2427.2001.00693.x
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  • 3
    Electronic Resource
    Electronic Resource
    Structural and functional responses of benthic macroinvertebrates to acid precipitation in two forested headwater streams (Vosges Mountains, northeastern France) (2000)
    Springer
    Hydrobiologia 418 (2000), S. 25-31 
    Details
    ISSN: 1573-5117
    Keywords: acidification ; benthic invertebrates ; community structure ; leaf decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract From December 1996 to August 1997, beech litter breakdown and stream benthic macroinvertebrate communities were investigated to assess the effects of acidic precipitation on community structure and function in two second-order headwater streams of the Vosges Mountains (NE France). Because of microscale changes in bedrock mineral composition, one of the streams was acidified (mean pH=4.53, mean total Al=421 μg.l-1) and the other circum-neutral (mean pH=7.23, mean total Al=36 μg.l-1). Results showed that both litter breakdown rate and macroinvertebrate community structure were drastically affected under acidic conditions. The rate of leaf litter breakdown decreased by nine times in the acidic stream. Benthic sampling showed that scrapers were totally eradicated and both gathering and filtering collectors were drastically reduced. Such drastic effects appear to be the consequences of the toxicity of acid water including both proton and aluminum toxicity. A decrease in shredder abundance and a shift from the efficient acid-sensitive Amphipoda Gammarus fossarum to acid-tolerant Nemouroidea (mainly Leuctra sp.) was observed in the acidic stream. Our results indicate that freshwater acidification significantly alters the action of shredders processing leaf litter in the acidic stream. Consequently, interactions between structural and functional responses to acidification probably have profound consequences on the efficiency of acidified stream ecosystems, which in return may alter downstream functioning.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1003805902634
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  • 4
    Electronic Resource
    Electronic Resource
    Synthesis of 3-Methoxy- and 3-(β-D-Glucopyranosyloxy)flavylium Ions. Influence of the flavylium substitution pattern on the reactivity of anthocyanins in aqueous solution (1994)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 77 (1994), S. 1595-1610 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of 3-glycosyloxylated flavylium ions (anthocyanins), in particular of callistephin (4), a natural anthocyanin, is described. The structural transformations in aqueous solution and molecular complexation with chlorogenic acid (7) and caffeine (8) of the synthesized pigments 3 and 4 are investigated and compared to those of the corresponding 3-methoxyflavylium ions 1 and 2 and to those of oenin (5) and malvin (6), two very common natural anthocyanins. The results are discussed in terms of the role played by the glycosyloxy residues in the chemical properties of anthocyanins. Anthocyanin molecular complexation (copigmentaion) is quantitatively investigated by UV/VIS spectroscopy and 1H-NMR. In particular, the UV/VIS spectroscopic data are interpreted using a general theoretical treatment, which, e.g., allows to demonstrate the formation of molecular complexes between the colourless forms of an anthocyanin and 8.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19940770616
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  • 5
    Electronic Resource
    Electronic Resource
    3′-(β-D-Glycopyranosyloxy)flavylium Ions: Synthesis and investigation of their properties in aqueous solution. Hydrogen bonding as a mean of colour variation (1997)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 80 (1997), S. 398-413 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This work describes a straightforward synthesis of two 3′-(β-D-glycopyranosyloxy)flavylium ions thought to be good models of natural anthocyanins (pigments). For both pigments and for the non-glycosylated flavylium ion taken as a reference, H2O addition and proton-transfer reactions as well as formation of molecular complexes with chlorogenic acid and caffeine (copigmentation) are quantitatively investigated in mildly acidic aqueous solution. A remarkable affinity of caffeine for the trans-chalcone form of the pigments is demonstrated. Moreover, the differences in the flavylium pKa values are interpreted in terms of possible intramolecular H-bonding between the glycosyl residue and the chromophore. The discussion is then extended to a series of malonylated anthocyanins recently reported for their unusual pigmentation properties. A possible role for the malonyl group (frequently encountered in the structure of naturally occurring anthocyanins) in plant colour expression is outlined for the first time.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19970800206
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