13C-nmr spectroscopic investigation of two yeast cell wall β-D-glucans

By means of alkaline extraction of the cell walsl of the yeasts Saccharomyces cerevisiae and Canadida albicans, water-insoluble glucans were obtained. Methylation analysis and ¹³C-nmr investigation in dimethyl sulfoxide solution revealed the similar chemical structure of these glucans, being composed of β(1 → 3) glycosidically linked D -glucopyranosyl units with a small amount of β(1 → 6) linkages. More detailed study in dilute alkaline solutions and in the gel state at neutral pH, however, showed that an ordered helical conformation of the glucan chain is less stable in the case of the S. cerevisiae glucan in comparison with that of C. albicans. Measurements of the shift of the absorption maximum of the glucan complexes with Congo Red also demonstrated such difference. The S. cerevisiae glucan was also inable to form a gel at neutral pH. The difference in stability of helical conformation of the glucans is explained on the basis of the methylation analysis, so that the S. cerevisiae glucan possesses longer side chains, which hinder its adoption of a stable helical conformation.