303Downloaded by [University of Otago] at 07:05 18 July 2015 304 J. Wu et al.A polysaccharide was purified from brown alga Kjellmaniella crassifolia, and its precise structure was deduced on the basis of sequence analysis of oligosaccharide fragments obtained from mildly and strongly acidic hydrolysis of the polysaccharide. Electrospray ionization collision-induced dissociation tandem mass spectrometry (ESI-CID-MS/MS) was used to identify the structural features of the resultant oligosaccharides. The side chain oligosaccharides were composed of α-1,3-linked 4-O-sulfated fucose and α-1,3-linked 2,4-O-disulfated fucose, while the backbone oligosaccharides consisted of the disaccharide repeating unit of β-1,4-linked glucuronic acid and α-1,2-linked mannose. Thus, the fucoidan was determined to be a sulfated fuco-oligosaccharide branched glucuronomannan.