Structure and Conformation Behavior of a Glucan from Spores of Ganoderma lucidum (Fr.) Karst.

ABSTRACT

A novel polysaccharide designated as beta-D-glucan LB-NB, [alpha](D)(21) -24.52(0)(c =0.81, H(2)O)and Mr 4.7x10(4), was isolated and purified from a 0.5 mol/L sodium hydroxide extract of the sporoderm-broken spores of Ganoderma lucidum. The results of NMR experiments, total hydrolysis, methylation analysis and Smith degradation of LB-NB showed that it possesses a backbone consisting of(1right curved arrow 3)- beta-D-glucosyl residues, about two out of nine glucosyl residues being substituted at O-6 by single glucosyl groups. The conformational behavior of LB-NB was studied. Measurements by specific rotations and viscometry showed that the glucan LB-NB takes an ordered structure in water or lower concentration(<0.05 mol/L)alkaline solution and dissolves as random coil in higher concentration(>0.1 mol/L)alkaline solution or in dimethyl sulfoxide(Me(2)SO). The ordered conformation melts into flexible chains with the increase of the concentration of alkali or the V(DMSO)(v/v)of H(2)O-Me(2)SO mixture. The former dissociation is reversible and the later is irreversible. The complex-formation with Congo red indicated that the LB-NB takes neither triple-stranded helical nor randomly coiled conformation in neutral or slightly alkaline solution, and most probably, it should contain single helical structure in aqueous solution. According to immunological test, the LB-NB showed remarkable activity of stimulating the proliferation of T-Cells in vitro, giving a good example for Kulicke's statement.