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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    European food research and technology 210 (2000), S. 268-272 
    ISSN: 1438-2385
    Keywords: Key words Apple varieties ; Flavanols ; Chlorogenic acid ; Polyphenol oxidase ; Enzymatic browning
    Source: Springer Online Journal Archives 1860-2000
    Topics: Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract  Ten apple varieties, harvested at commercial maturity, were analysed, paying special attention to the level of phenolic compounds and polyphenol oxidase (PPO) activity. The results pointed to great quantitative differences in the composition of the apple varieties, and particularly in their phenolic contents. Their total polyphenol content ranged from 2.3 to 3.6 g/kg. Chlorogenic acid was the main phenolic compound found in the varieties studied, and its concentrations varied from 30 to 430 mg/kg, and were 4–20 times higher than those of catechins. Only in Szampion and Elstar were the concentrations of catechins higher. Amongst the flavanol monomers, the main compound was (–)epicatechin, whose concentration varied from 18 to 89 mg/kg. The (+)catechin concentration ranged from 4 to 21 mg/kg. The dominant proanthocyanidins were oligomers up to trimers. In Warta apples, the concentrations of these oligomers were about 3 times higher than those of monomers. The level of PPO activity ranged from 270 units (U)/g in Szampion to 3120 U/g in Warta. No correlation was found between the concentrations of certain phenolic compounds, nor between PPO activity and phenolic or ascorbic acid concentrations. The results gave important information regarding the best use of the apple varieties investigated, i.e. for direct consumption due to their high nutritional value, or for processing.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-1017
    Keywords: Key words Neuropeptide ; Conformational dynamics ; Time-resolved fluorescence spectroscopy ; Binding studies
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Physics
    Notes: Abstract The structural dynamics of the flexible neuropeptide galanin in solution were studied by Förster resonance energy transfer measurements at different temperatures by time-resolved fluorescence spectroscopy to determine its conformational heterogeneity. Endogenous tryptophan at position 2 acted as the fluorescent donor and the non fluorescent acceptor dinitrophenyl or the fluorescent acceptor dansyl were selectively attached to lysine 25 in porcine galanin. The coexistence of different structures of the neuropeptide galanin in trifluoroethanol solution was revealed by the model independent analysis of the distribution of relaxation times from the time-resolved resonance energy transfer data. Multiple conformational states are reflected by distinct end-to-end distance populations. The conformations differ in mean donor-acceptor distance by about 15 Å, and are consistent with the extended and folded backbone conformations of two α-helical regions separated by a flexible hinge. The effect that the labelling of galanin has on binding to the receptor was also evaluated. DNP-galanin showed the same high affinity to galanin receptors as unlabelled galanin, whereas DNS-galanin had significantly reduced affinity.
    Type of Medium: Electronic Resource
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