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| Titel: |
Communication: Relaxed 2/1-Helical Conformation of Type II Chitosan has a Tetrasaccharide Motif |
| Auteur: |
Okuyama, Kenji Osawa, Kunitake Hanafusa, Yoshiki Noguchi, Keiichi Ogawa, Kozo |
| Verschenen in: |
Journal of carbohydrate chemistry |
| Paginering: | Jaargang 19 (2000) nr. 6 pagina's 789-794 |
| Jaar: |
2000 |
| Inhoud: |
Chitosan, the N-deacetylated chitin, has two crystal forms. One is hydrated and the other is anhydrous. The main chain in both is known to adopt an extended ribbon-like 2/1 helix with about 10.4 Å c-repeat per disaccharide.1,2 This is the well known canonical structure of (1→4) linked cellulose, chitin and mannan. Among them, chitosan has a remarkable ability to form specific complexes with organic and inorganic acids in addition to transition and post-transition metal ions.3-7 The complexes studied so far are classified into two groups: the above canonical structure (Type I), and an “8-fold” (8/3 or 8/5) helix4 with long 40 Å c-repeat (Type II). The structural details of the latter are yet unknown. The complexes containing monocarboxylic acids, such as formic, acetic and propionic acids, belong to Type II; interestingly, they all undergo a spontaneous removal of the acids accompanying water molecules.8 As a result, the Type II complex in the solid state changes to the anhydrous form which corresponds to Type I.2 Therefore, the Type II helix must be characterized properly in order to understand the mechanism of crystalline transformation of chitosan from the hydrated to the anhydrous form via chitosan/monocarboxylic acid complexes. Based on recent X-ray diffraction analysis, in this communication, we propose that Type II chitosan has a relaxed 2/1-helical conformation that exploits a tetrasaccharide rather than a monosaccharide as its asymmetric motif. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 4 van 9 gevonden artikelen
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