title: Chain conformation of water-insoluble hyperbranched polysaccharide from fungus.
abstract: Water-insoluble polysaccharide (TM3a), extracted from sclerotia of Pleurotus tuber-regium, was identified as a hyperbranched beta-d-glucan from the results of one- and two-dimensional NMR and GC-MS analysis. The degree of branching of TM3a is 65.5%. TM3a was fractionated by using a non-solvent addition method into 14 fractions, and its solution properties in 0.25 M LiCl/dimethylsulfoxide (DMSO) solution were studied systematically by using static laser light scattering, dynamic light scattering, and viscometry at 25 degrees C. The dependences among the values of intrinsic viscosity ([eta]), radius of gyration (<S2>z 1/2), and hydradynamic radius (Rh) on weight-average molecular weight (Mw) were found as the following: [eta] = 0.46Mw0.30+/-0.01, <S2>z 1/2 = 4.79 x 10-2Mw0.43+/-0.04, and Rh = 5.01 x 10-2Mw0.41+/-0.02 in the Mw range from 1.94 x 105 to 2.06 x 107 for TM3a in a 0.25 M LiCl/DMSO solution at 25 degrees C. The current theory of polymer solution was applied to explain the relationship among the fractal dimension, ratio of geometric to hydrodynamic radius (rho = <S2>z 1/2/Rh), and MwA2/[eta] of TM3a. The results indicated that TM3a existed as a compact chain conformation with a sphere-like structure in LiCl/DMSO solution. Furthermore, by using transmission electron microscopy, we observed directly the spherical molecules with an average diameter of 23.0 +/- 1.8 nm.
authors.affiliation: Department of Chemistry, Wuhan University, Wuhan, China.
authors.forename: Yongzhen
authors.initials: Y
authors.lastname: Tao
authors.forename: Lina
authors.initials: L
authors.lastname: Zhang
authors.forename: Fan
authors.initials: F
authors.lastname: Yan
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Wu
mesh_terms: D017709:Fractals; D046529:Microscopy, Electron, Transmission; D020076:Pleurotus / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry*; D012995:Solubility; D017550:Spectroscopy, Fourier Transform Infrared; D014867:Water / Q000737:chemistry*
chemical_list: D011134:Polysaccharides; D014867:Water