title: Small-angle X-ray and light scattering analysis of multi-layered Curdlan gels prepared by a diffusion method.
abstract: Curdlan, a microbial polysaccharide, forms a multi-layered gel consisting of four layers with different turbidity when its alkaline solution is dialyzed against aqueous solutions containing Ca2+(diffusion-set gel). The present study clarified the microstructure of each layer of the diffusion-set Curdlan gel by small-angle X-ray scattering (SAXS) and small-angle light scattering (SALS). The SAXS data showed that Curdlan chains assume a helical ordered conformation in the gel and that the gel consists of the fibrils formed by the association of Curdlan chains and the aggregates of fibrils. The SAXS results also indicated that the gelation is induced by the formation of a network of Ca2+-cross-linked fibrils in the outer region of the gel, whereas by the network formation of the aggregation of fibrils in the neutralization process in the inner region of the gel. A structural anisotropy of the gel was investigated by analysis of two-dimensional SAXS images, showing that the fibril is oriented circumferentially in the outer region of the cylindrical gel, whereas it is oriented randomly in the inner region of the gel. The SALS data showed that a characteristic length of an inhomogeneous structure in the turbid layers is of the order of micrometers. The observed spatial variation of the microscopic structure is caused by the difference in the paths of pH and [Ca2+] traced in the gelation process.
authors.affiliation: Division of Molecular Science, Graduate School of Science and Technology, Gunma University, Kiryu 376-8515, Japan. Electronic address: maki@gunma-u.ac.jp.
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Maki
authors.affiliation: Faculty of Advanced Life Science, Hokkaido University, Sapporo 060-0810, Japan.
authors.forename: Kazuya
authors.initials: K
authors.lastname: Furusawa
authors.affiliation: Division of Molecular Science, Graduate School of Science and Technology, Gunma University, Kiryu 376-8515, Japan.
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Dobashi
authors.affiliation: Division of Biophysical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Sugimoto
authors.affiliation: Division of Biophysical Engineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan.
authors.forename: Katsuzo
authors.initials: K
authors.lastname: Wakabayashi
keywords: Curdlan; Gel; Small-angle X-ray scattering; Small-angle light scattering