The main structural features of the water-soluble arabinoxylan-protein complex isolated from rye bran were evaluated by means of methylation analysis and 13C NMR spectroscopy. A highly branched arabinoxylan with Ara f residues in mono- and di-substitution positions and side chains terminated with Xylp groups represents the main component associated with a serine- and glycine-rich cell-wall protein. More than 30% of the arabinose is linked in various positions probably as oligosaccharide side-chains and/or branched (1 → 5)-arabinan. The molecular parameters were estimated by HPGPC as well as by gel chromatography combined with viscometry and light-scattering. The high molecular weight fraction close to the exclusion volume (MW > 106), which is shifted after treatment with Pronase to the region 104 < MW < 106, is considered to consist of fragments of the native cell-wall matrix with arabinoxylan chains probably linked to a protein core.
