| Lentinus edodes as the special local product is an abundant natural food resource in China. It has long been used in traditional herb except for its nutritional values. It is well established that the polysaccharide fractions of lentinan has many functions such as antitumor and immunological enhancement. It has been found in recent years that the antitumor activities of polysaccharides are correlated to their chain conformations in solution (stiff or coil, single-, double- or triple helix, aggregate), which are mainly characterized by polymer solution theory and modern method in polymer science. In this work, lentinan, a kind of water-soluble polysaccharide, was extracted from Lentinus edodes by biotechnics. The chemical structure, chain conformation in solution, and antitumor activity of polysaccharide were studied, and the correlation between structure and bioactivities were discussed. Therefore the research is in a cross field of polymer physics and biochemistry.The creative points of this work are as follows. (1) The dependences of intrinsic viscosity [] and radius of gyration 1/2 on Mw for Lentinan in 0.9% NaCl aqueous solution and in DMSO were established based on the theory of polymer solution and advanced instruments. (2) It is confirmed that the helix-coil transition for the B-D-glucan in the mixture of water / DMSO occurred from 0.82 to 0.85 of the volume fraction of the DMSO. (3) The anti-tumor activity of Lentinan with different molecular weights was evaluated, showing that the triple helix Lentinan with Mw of 5.71 x105 exhibited higher antitumor activity in vivo and vitro without any damage to the normal cell.The main contents and conclusions in this thesis are divided into the following parts.B-(1-3)-D-glucan was isolated from Lentinus edodes by extracting with 0.8% NaOH / 0.02% NaBH4 and 5% NaOH / 0.05% NaBH4 respectively to obtain glucans L-FV-IA and L-FV-IB. The chemical structure of the sample L-FV-IB was determined by infrared (IR) and 13C NMR to be a B-(1-3)-D-glucan with (1-6) branching , namely two branched residues for every five D-gluopyranosyl residues. The glucan L-FV-IB was degraded into seven fractions of different molecular weights by ultrasonic irradiation, and further fractionated, each into three parts, by precipitation from water to acetone at the room temperature. Weight-average molecular weight (Mw), radius of gyration (1/2), and intrinsic viscosity ([]) of the B-D-glucan and its fractions in 0.9% NaCl aqueous solution and dimethylsulfoxide (DMSO) were measured by multi-angle laser light scattering (LLS), size exclusionchromatography combined with multi-angel laser light scattering (SEC-LLS), and viscometry. Mw dependence of [] and radius of gyration 1/2 for the glucan in 0.9% NaCl aqueous solution at 25 C were established to be [17] = 2.94 x 10-7Mw1.58 (cm3 g-1) (Mw < 6.0 x 105), [] = 2.30x10-5Mw125(cm3 g-1) (Mw>6.0x 105) and 1/2= (4.35+0.3) x 10-3Mw0.75+0.02(nm), respectively. However, the dependences of intrinsic viscosity [] on Mw for the glucan in DMSO was established to be [] = 0.112 Mwa54 (cm3 g-1). Based on YFY theory for wormlike chain model, the conformational parameters of the glucan L-FV-IB were obtained to be 2240 + 100 nm-1, 100 + 10 nm and 0.30 + 0.1nm for molar mass per unit contour length (ML), persistence length (q), and contour length per main-chain glucose residue (h), respectively, which agree closely with theory data of triple-helical chains and reported parameters for triple-helix schizophyllan in 0.01M NaOH aqueous solution. However, the parameters of the B-D-glucan agree with theory data of single-flexible chains. The results indicated that the glucan in 0.9% NaCl aqueous solution exist as triple-helical chains with high rigidity, and in DMSO as single-flexible chains.The values of Mw, 1/2, [] and the special optical rotations at 589nm [a]D of lentinan in 0.2M NaCl aqueous solution, dimethylsulfoxide (DMSO) and water / DMSO mixtures were measured by LLS, SEC-LLS, viscometry, and polarimeter. The results indicated that the...
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