Reserch On Isolation,Purification,Structure Characteristics And Solution Properties Of The Polysaccharide From Tremella Fuciformis

A water-soluble polysaccharide was extracted from Tremella fuciformis Berk. Crude Tremella fuciformis polysaccharide was gained by boiling in hot-water, precipitating using ethanol, removing proteins using papain-Sevage method. Then the crude polysaccharide was applied to DEAE-52 cellulose colume and further purified through Sephacryl S-400 column, followed by dialysis, lyopilization. The resulting sample was named as TFP1. Total sugar and uronic acid contents of TFP1 were determined by phenol-sulfuric acid method and m-hydroxydiphenyl combined with sulfuric acid method using glucose and glucuronic acid as standard respectively. UV spectrum showed that no protein or nucleic acid presented in TFP1. The results of the PMP precolumn derivatization HPLC analysis, FT-IR spectroscopy and NMR spectrum showed that TFP1 was an acidic heteropolysaccharide containing mannose, glucuronic acid, xylose and fucose with the molar ratio of 5.78:0.7:1.1:1(containing a small amount of glucose), and the spectrums indicated that anomeric carbon of TFP 1 was a-configuration. The Mw, polydispersity index and root-mean square radius of polymer calculated from Zimm plot was 5.832×106Da,1.005,193.1 nm in NaCl solution respectively, which indicated that TFP1 was a homogeneous and rigid chain macromolecule. The intrinsic viscosity([η]) was used to determined by both of the Huggins and Kraemer functions was 1508.3 mL/g which indicated that the polymer molecules was considered to occupy a relatively large hydrodynamic volume in NaCl solution. I2-KI assay also suggested that many branched chains attached to the backbone chain which was composed of mannose residues. After Congo red dye was added to sample at various concentration of alkali, the variation curves of maximum absorption wavelength of mixture decreased gradually with increasing of NaOH concentration and no triple helical structure was detected in TFP1. Atomic force microscopy was used to characterize surface topology and visualize the orientation and spatical distribution of molecules absorbed to mica surface. TFP1 was observed (?)mpact chains conformation unexpectedly, and it was probable that the structure characteristics of GlcUA residue, abundant hydrogen bonds and hyperbranch tend to make macromolecule form spherical conformation.In brief, TFP1 was an acidic and homogeneous heteropolysaccharide mainly composed of four monosaccharide residues and the anomeric carbons were a-configuration. Solution properties research proved that the hyperbranched polysaccharide existed in the solution as an extended rigid chain but without triple helical conformation.