Critical concentrations of α-(1→3)-D-glucan L-FV-Ⅱ from Lentinus edodes were studied by viscometry andfluorescence probe techniques. The dependence of the reduced viscosity on concentration of the glucan in 0.5 mol/L NaOHaqueous solutions with or without urea showed two turning points corresponding to the dynamic contact concentration cs andthe overlap concentration c* of the polymer. The values of cs and c* were found to be 1×10-3 g cm-3 and 1.1×10-2 g cm-3

respectively

for L-FV-II in 0.5 mol/L NaOH aqueous solutions.The two critical concentrations of L-FV-II in 0.5 mol/L NaOH aqueous solutions were also found to be 1.2×10-3g cm-3 for cs and 9.2×10-3g cm-3 for c8 from the concentration dependence of phenanthrene fluorescence intensities.The overlap concentration c* of L-FV-II in 0.5 mol/L NaOH aqueous solutions was lower than that of polystyrene with same molecular weight in benzene

owing to the fact that polysaccharide rends to undergo aggregation caused by intermolecular hydrogen bonding.A normal viscosity behavior of L-FV-II in 0.5mol/L urea/0.5 mol/L NaOH aqueous solutions can still be observed in an extremelt low concentration range at 25℃.