Structure and Conformation Behavior of a Glucan from

Structure and
Conformation Behavior of a Glucan from Spores of Ganoderma
lucidum (Fr.) Karst
BAO
Xing-Feng, DONG Qun, FANG Ji-Nian^*
(Shanghai Institute of Meteria Medica, the Chinese Academy of Science, Shanghai
200031, China)

Abstract    A novel
polysaccharide designated as β-D-glucan LB-NB,[α]_D²¹
-24.52⁰(c =0.81, H₂O)and Mr 4.7×10⁴,
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(1→3)-β-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(Me₂SO). The ordered
conformation melts into flexible chains with the increase of the concentration
of alkali or the V_DMSO(v/v)of H₂O-Me₂SO
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^[1].
Key words    glucan；structure；conformation；immunological activity

^*Corresponding author： Tel, 021-64311833-601； e-mail, [email protected]