Abstract: Aacidic heteropolysaccharide (F Ⅱ), which is composed of D-mannose, D-xylose, D-glucose and glucuronic acid, was isolated from the fruiting body of Auricularia auricula-judae, and separated into 8 fractions by reprecipitation.The weight average molecular weights M_w, number average molecular weights M_n and second viriai coefficients A₂ of fractions and unfrac-tioned samples in 0.5 mol/L NaCl/10%cadoxen (C) were measured by low angle laser light scattering and membrane osmometry.The values of M_w and M_n of the acidic heteropolysaccharide were obtained to be:5.88×10⁵ and 1.43 ×10⁵.Intrinsic viscosities [η] were investigated on fractioned samples in aqueous 0.5 mol/L NaCl (A), 0.2 mol/L Na₂SO₄/0.01 mol/Lphosphate buffer (B) and (C) at 30℃.The Mark-Houwink equations were established as [η] = 0.235 M_w^0.48 (A), [η] = 7.61×10^-2M_w^0.57 (B) and [η] = 6.44×10^-2M_w^0.59 (C).The unperturbed dimensions〈S²⁰ and K_θ are respectively 12.1 ×10^-18 cm²mol g^-1 and 0.175 cm³g^-1.We conclude that the acidic heteropolysaccharide behaves as a slightly stiffened random coil chain in aqueous solution.

Key words: Auricularia auricula-judae polysaccharide, Light scattering, Membrane osmometry, Unperturbed dimension, Solution property