title: Anisotropic structure of calcium-induced alginate gels by optical and small-angle X-ray scattering measurements.
abstract: It was more than 50 years ago that an appearance of birefringence in alginate gels prepared under cation flow was reported for the first time, however, the anisotropic structure of the alginate gel has not been studied in detail. In the present study, anisotropic Ca-alginate gels were prepared within dialysis tubing in a high Ca(2+)-concentration external bath, and optical and small-angle X-ray scattering (SAXS) measurements were performed to characterize the structure of the gel. The observations of the gel with crossed polarizers and with circular polarizers revealed the molecular orientation perpendicular to the direction of Ca(2+) flow. Analyses of the SAXS intensity profiles indicated the formation of rod-like fibrils consisting of a few tens of alginate molecules and that the anisotropy of the gel was caused by the circumferential orientation of the large fibrils. From the observed asymmetric SAXS pattern, it was found that the axis of rotational symmetry of the anisotropic structure was parallel to the direction of Ca(2+) flow. The alignment factor (A(f)) calculated from the SAXS intensity data confirmed that the orientation of the fibrils was perpendicular to the direction of Ca(2+) flow.
authors.affiliation: Department of Chemistry and Chemical Biology, Graduate School of Engineering, Gunma University , Kiryu, Japan. maki@chem-bio.gunma-u.ac.jp
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Maki
authors.forename: Kei
authors.initials: K
authors.lastname: Ito
authors.forename: Natsuki
authors.initials: N
authors.lastname: Hosoya
authors.forename: Chikayoshi
authors.initials: C
authors.lastname: Yoneyama
authors.forename: Kazuya
authors.initials: K
authors.lastname: Furusawa
authors.forename: Takao
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Dobashi
authors.forename: Yasunobu
authors.initials: Y
authors.lastname: Sugimoto
authors.forename: Katsuzo
authors.initials: K
authors.lastname: Wakabayashi
mesh_terms: D000464:Alginates / Q000737:chemistry* / Q000528:radiation effects; D016880:Anisotropy; D001672:Biocompatible Materials / Q000737:chemistry*; D002118:Calcium / Q000378:metabolism*; D005782:Gels / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D008027:Light; D055620:Optical Phenomena; D053838:Scattering, Small Angle; D014867:Water / Q000737:chemistry
chemical_list: D000464:Alginates; D001672:Biocompatible Materials; D005782:Gels; D014867:Water; D002118:Calcium