Molecular and Crystal Structure of a Chitosan-Zinc Chloride Complex.

We determined the molecular and packing structure of a chitosan-ZnCl complex by X-ray diffraction and linked-atom least-squares. Eight D-glucosamine residues-composed of four chitosan chains with two-fold helical symmetry, and four ZnCl molecules-were packed in a rectangular unit cell with dimensions = 1.1677 nm, = 1.

Surface structure of chitosan and hybrid chitosan-amylose films-restoration of the antibacterial properties of chitosan in the amylose film.

The surface structure of films prepared by casting aqueous solutions of mixtures of water soluble chitosan (WSC) and amylose as well as a fully deacetylated chitosan was studied. Zeta potential measurements indicated that the surface of WSC and fully deacetylated chitosan films is positively charged but very weakly, whereas, a film of amylose blended with WSC exhibited an obvious positive charge. X-ray photoelectron spectra of these films suggest that less amino groups are exposed on the surface of WSC and fully deacetylated chitosan films, whereas, more amino groups are exposed on the surface of a WSC film blended with amylose.

Effect of addition of water-soluble chitin on amylose film.

Amylose films blended with chitosan, which were free from additives such as acid, salt, and plasticizer, were prepared by casting mixtures of an aqueous solution of an enzymatically synthesized amylose and that of water-soluble chitin (44.1% deacetylated). The presence of a small amount of chitin (less than 10%) increased significantly the permeability of gases (N2, O2, CO2, C2H4) and improved the mechanical parameters of amylose film; particularly, the elastic modulus and elongation of the blend films were larger than those of amylose or chitin films.

Three D structures of chitosan.

Crystal structures of two polymorphs of chitosan, tendon (hydrated) and annealed (anhydrous) polymorphs, have been reported. In both crystals, chitosan molecule takes up similar conformation (Type I form) to each other, an extended two-fold helix stabilized by intramolecular O3-O5 hydrogen bond, which is also similar to the conformation of chitin or cellulose. Three chitosan conformations other than Type I form have been found in the crystals of chitosan-acid salts.

Plausible molecular and crystal structures of chitosan/HI type II salt.

Chitosan/HI type II salt prepared from crab tendon was investigated by X-ray fiber diffraction. Two polymer chains and 16 iodide ions (I(-)) crystallized in a tetragonal unit cell with lattice parameters of a = b = 10.68(3), c (fiber axis) = 40.

Molecular and crystal structures of chitosan/HI type I salt determined by X-ray fiber diffraction.

The three-dimensional structure of chitosan/HI type I salt was determined by the X-ray fiber diffraction technique and linked-atom least-squares refinement method. Two polymer chains and four iodide ions (I(-)) crystallized in a monoclinic unit cell with dimensions a = 9.46(2), b = 9.

Fourth 3D structure of the chitosan molecule: conformation of chitosan in its salts with medical organic acids having a phenyl group.

Chitosan salts with two medical organic acids having phenyl groups (salicylic and gentisic acids) exhibited fiber diffraction patterns of a new type of crystal which does not compare with known types I and II. The crystals, called type III salts, showed a fiber repeat of 2.550 nm and a meridional reflection at the 5th layer line.

Dependence of the mechanical properties of a pullulan film on the preparation temperature.

The mechanical properties of pullulan films prepared at various temperatures were investigated. The films prepared at high temperatures (40 degrees C and 60 degrees C; H-films) did not show any clear plastic deformation in tensile test, indicating that they were brittle. In contrast, those prepared at low temperatures (4 degrees C, 13 degrees C, and 25 degrees C; L-films) showed such deformation.

Two different molecular conformations found in chitosan type II salts.

The type II structure of chitosan acidic salts prepared from crab tendon in solid state was studied using an X-ray fiber diffraction technique together with the linked-atom least-squares (LALS) technique. The cylindrical Patterson method was applied to confirm the molecular conformation of the chitosan. It was shown that there are two different helical conformations for type II salts.

X-ray structure analysis of the sodium salt of beijeran.

The three-dimensional structure of the sodium salt of beijeran has been determined by X-ray fiber diffraction analysis. The acidic polysaccharide forms an extended twofold helix. Two chains are nestled tightly in a monoclinic unit cell of dimensions a=12.