title: Fourth 3D structure of the chitosan molecule: conformation of chitosan in its salts with medical organic acids having a phenyl group.
abstract: 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. These results coupled with a conformational analysis indicate the chain conformation of chitosan with the salts to be a 5/3 helix, this helix differing from those of type I (an extended two-fold helix) and type II (a relaxed two-fold helix or a 4/1 helix). The fiber patterns of all the type III salts were similar. This observation has also been found with type II salts and is an indication that the acid ions are not arranged in regular positions in the crystals. A comparison of solid-state 13C-NMR spectra of the gentisic acid salt and the aspirin salt, which could not be crystallized, suggests that, in the latter salt, the chitosan molecules also formed a 5/3 helix.
authors.affiliation: Research Institute for Advanced Science and Technology, Osaka Prefecture University, Sakai, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Kawahara
authors.forename: Toshifumi
authors.initials: T
authors.lastname: Yui
authors.forename: Kunio
authors.initials: K
authors.lastname: Oka
authors.forename: Peter
authors.initials: P
authors.lastname: Zugenmaier
authors.forename: Shiho
authors.initials: S
authors.lastname: Suzuki
authors.forename: Shinichi
authors.initials: S
authors.lastname: Kitamura
authors.forename: Kenji
authors.initials: K
authors.lastname: Okuyama
authors.forename: Kozo
authors.initials: K
authors.lastname: Ogawa
mesh_terms: D000143:Acids / Q000737:chemistry; D002686:Chitin / Q000031:analogs & derivatives* / Q000737:chemistry*; D048271:Chitosan; D006860:Hydrogen Bonding; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D008968:Molecular Conformation; D009930:Organic Chemicals / Q000737:chemistry*; D012492:Salts / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D000143:Acids; D009930:Organic Chemicals; D012492:Salts; D002686:Chitin; D048271:Chitosan