Structural determination of an exocellular mannan from Rhodotorula mucilaginosa YR-2 using ab initio assignment of proton and carbon NMR spectra.

The structure of the title mannan was determined exclusively by NMR. Because of the short relaxation time of the native mannan (100 kDa), a partially hydrolyzed mannan (10 kDa) was used for proton assignments by COSY, to correlate proton and carbon signals by HMQC, and to determine linkage positions between residues by HMBC. A further hydrolyzed mannan (oligomers of approximately 1.5 kDa) was used to determine the anomeric configuration, using Wilker's quasi-3D method [Wilker, W.; Leibfritz, D. Magn. Reson. Chem. 1995, 33, 632-638]. The procedure presented here can be used to determine the structure of any polysaccharide.