Kawahara Makoto, Yui Toshifumi, Oka Kunio, Zugenmaier Peter, Suzuki Shiho, Kitamura Shinichi, Okuyama Kenji, Ogawa Kozo
Research Institute for Advanced Science and Technology, Osaka Prefecture University, Sakai, Japan.
Biosci Biotechnol Biochem. 2003 Jul;67(7):1545-50. doi: 10.1271/bbb.67.1545.
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.
壳聚糖与两种含苯基的医用有机酸（水杨酸和龙胆酸）形成的盐呈现出一种新型晶体的纤维衍射图谱，与已知的 I 型和 II 型不同。这种晶体被称为 III 型盐，其纤维重复周期为 2.550 nm，在第 5 层线处有子午线反射。这些结果与构象分析表明，壳聚糖与盐形成的链构象为 5/3 螺旋，这种螺旋不同于 I 型（伸展的双螺旋）和 II 型（松弛的双螺旋或 4/1 螺旋）。所有 III 型盐的纤维图谱相似。II 型盐也有此现象，这表明酸离子在晶体中并非排列在规则位置。对无法结晶的龙胆酸盐和阿司匹林盐的固态 13C - NMR 光谱进行比较表明，在后一种盐中，壳聚糖分子也形成了 5/3 螺旋。
