Lentinan samples,(1→3)-β-D-glucans containing 4.6-15.2 wt% proteins,coded as L-I_1 L-I_2 L-I_3 and L-I_4(L-I)were isolated from four kinds of Lentinus edodes.These glucans were treated with acetone to remove the protein in orderto obtain free protein glucans coded as LNP-I_1,LNP-I_2.LNP-I_3 and LNP-I_4(LNP-I).The free-protein polysaccharideswere sulfated to give derivatives(S-LNP-I)with degree of substitution(DS)from 0.4-0.8.The structural features andweight-average molecular weight(M_w)of the samples were investigated by using infrared spectroscopy,elemental analysis,~(13)C-NMR,size exclusion chromatography combined with laser light scattering(SEC-LLS)and viscometry.The effects ofstructure and conformation of the polysaccharides on antitumor activities were assayed in vivo(Sarcoma 180 solid tumors)and in vitro(Sarcoma 180,HL-60,MCF-7 and Vero tumors).The results indicated that the predominant species of thesamples L-I and LNP-I in 0.2 mol/L NaCl aqueous solution existed as triple-helical chains with high rigidity and in dimethylsulfoxide(DMSO)as single-flexible chains.Interestingly,the antitumor activities of LNP-I are lower than those of the nativeglucans(L-I),whereas their sulfated derivatives have higher inhibition ratio against Sarcoma 180 than LNP-I.The resultsreveal that the binding of protein,sulfated modification and the triple helix conformation are important factors in theenhancement of the antitumor activities of polysaccharides on the whole. Lentinan samples, (1 → 3) -β-D-glucans containing 4.6-15.2 wt% proteins, coded as L-I_1 L-I_2 L-I_3 and L-I_4 (LI) were isolated from four kinds of Lentinus edodes. glucans were treated with acetone to remove the protein in orderto obtain free protein glucans coded as LNP-I_1, LNP-I_2.LNP-I_3 and LNP-I_4 (LNP-I). The free-protein polysaccharideswere sulfated to give derivatives (S- LNP-I) with degree of substitution (DS) from 0.4-0.8. The structural features and weight-average molecular weight (M_w) of the samples were investigated by using infrared spectroscopy, elemental analysis, ~ (13) chromatography combined with laser light scattering (SEC-LLS) and viscometry. The effects of structure and conformation of the polysaccharides on antitumor activities were assayed in vivo (Sarcoma 180 solid tumors) and in vitro (Sarcoma 180, HL-60, MCF-7 and Vero tumors). The results indicated that the predominant species of the samples LI and LNP-I in 0.2 mol / L NaCl aqueous solution existed as triple-h elical chains with high rigidity and in dimethylsulfoxide (DMSO) as single-flexible chains. transiently, the antitumor activities of LNP-I are lower than those of the native glucans (LI), whereas their sulfated derivatives have a higher inhibition ratio than Sarcoma 180 than LNP -I.The resultsreveal that the binding of protein, sulfated modification and the triple helix conformation are important factors in theenhancement of the antitumor activities of polysaccharides on the whole.