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Keywords:

  • carrageenan;
  • nuclear magnetic resonance;
  • oligosaccharide;
  • sequence;
  • structure

κ-Carrageenan was hydrolyzed with mild hydrochloric acid and separated into a series of oligosaccharides, the sequences and structures of which were investigated by double-quantum filtered correlation spectroscopy (DQF-COSY), total correlation spectroscopy (TOCSY), heteronuclear multiple-quantum coherence (HMQC), and heteronuclear multiple-bond correlation (HMBC) techniques, respectively. The chemical structures and conformations of the individual sugar residues were identified, as well as the sequential connectivity of the oligosaccharides. The interresidue nuclear Overhauser effects (NOEs)/rotating frame Overhauser effects (ROEs) revealed an ordered helical structure of the carrageenan oligosaccharide chains. Therefore, a general two-dimensional (2-D) NMR methodology for the unambiguous sequence and structure analysis of κ-carrageenan-derived oligosaccharides was established in this study.