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[摘要]：The hot water soluble green coffee arabinogalactans, representing nearly 7% of total coffee bean arabinogalactans, were characterized by H-1 and C-13 NMR and, after partial acid hydrolysis, by ESI-MS/MS. Data obtained showed that these are highly branched type II arabinogalactans covalently linked to proteins (AGP), with a protein moiety containing 10% of 4-hydroxyproline residues. They possess a beta-(1 --> 3)-Galp/beta-(1 --> 3,6)-Galp ratio of 0.80, with a sugars composition of Rha:Ara:Gal of 0.25:1.0:1.5, and containing 2 mol% of glucuronic acid residues. Beyond the occurrence of single alpha-L-Araf residues and [alpha-L-Araf-(1 --> 5)-alpha-L-Araf-(1-->] disaccharide residues as side chains, these AGPs contain unusual side chains at O-3 position of the beta-(1 --> 6)-linked galactopyranosyl residues composed by [alpha-L-Rhap-(1 --> 5)-alpha-L-Araf-(1 -->] and [alpha-L-Rhap-(1 --> 5)-alpha-L-Araf-(1 --> 5)-alpha-L-Araf-(1 --> ] oligosaccharides. Rhamnoarabinosyl and rhamnoarabinoarabinosyl side chains are reported for the first time as structural features of plant arabinogalactan-proteins. (C) 2008 Elsevier Ltd. All rights reserved. |
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