Lin Shan-Yang, Chien Jui-Lung
Biopharmaceutics Laboratory, Department of Medical Research and Education, Veterans General Hospital-Taipei, Taipei, Taiwan, Republic of China.
Pharm Res. 2003 Dec;20(12):1926-31. doi: 10.1023/b:pham.0000008038.38378.d6.
The processes of dehydration, rehydration, and solidification of trehalose dihydrate were examined to simulate it in the drying and wetting states.
Techniques included differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and Fourier transform infrared (FT-IR) microspectroscopy combined with thermal analysis. Trehalose dihydrate was pressed on one KBr pellet (IKBr method) or sealed within two KBr pellets (2KBr method) for FT-IR measurement.
On the DSC thermogram, the shoulder between 60 degrees C and 80 degrees C represented a transitional change because no weight loss occurred in this area of the TGA curve. The endothermic peak at 100 degrees C represented dehydration of trehalose dihydrate to anhydrous trehalose; a 9.5% weight loss in the TGA curve occurred from 81 degrees C. The thermal-dependent FT-IR spectra for trehalose dihydrate prepared by the IKBr method changed markedly with temperature in the 1800-1500 cm(-1) region during dehydration. IR peak intensity at 1687 cm(-1) assigned to the bending vibrational mode of solid-like water declined with temperature and decreased sharply at 67 degrees C. Another IR peak at 1640 cm(-1) associated with the bending of liquid water increased at 67 degrees C but disappeared at 79 degrees C as a result of water evaporation. Both peaks for the sample prepared by the 2KBr method changed dramatically at 64 degrees C; peak intensity at 1640 cm(-1) remained constant above 64 degrees C.
A new polymorphic transition of trehalose dihydrate was first evidenced at 64-67 degrees C from both DSC curves and thermal-related FT-IR spectra. This transitional temperature reflected the thermal-dependent transformation from solid-like water to liquid water in the trehalose dihydrate structure during dehydration. During rehydration, trehalose anhydrate was rehydrated to the dihydrate, and liquid water in the dihydrate structure was again transformed to solid-like water. The polymorphic transition within this temperature range seems to correlate with the bioprotective effect of trehalose dihydrate in preserving protein stability.
研究二水海藻糖的脱水、再水化和固化过程，以模拟其干燥和湿润状态。
技术包括差示扫描量热法（DSC）、热重分析（TGA）以及傅里叶变换红外（FT-IR）显微光谱结合热分析。二水海藻糖被压制成一个溴化钾片（1KBr法）或密封在两个溴化钾片之间（2KBr法）用于FT-IR测量。
在DSC热谱图上，60℃至80℃之间的肩峰代表一种转变变化，因为在TGA曲线的该区域没有重量损失。100℃处的吸热峰代表二水海藻糖脱水为无水海藻糖；TGA曲线在81℃时发生了9.5%的重量损失。通过1KBr法制备的二水海藻糖的热依赖FT-IR光谱在脱水过程中，在1800 - 1500 cm(-1)区域随温度有明显变化。1687 cm(-1)处归因于类固态水弯曲振动模式的红外峰强度随温度下降，并在67℃时急剧下降。另一个与液态水弯曲相关的1640 cm(-1)处的红外峰在67℃时增加，但由于水蒸发在79℃时消失。通过2KBr法制备的样品的两个峰在64℃时发生显著变化；1640 cm(-1)处的峰强度在64℃以上保持恒定。
从DSC曲线和热相关FT-IR光谱首次证明二水海藻糖在64 - 67℃发生了新的多晶型转变。这个转变温度反映了脱水过程中二水海藻糖结构中从类固态水到液态水的热依赖转变。在再水化过程中，无水海藻糖再水化形成二水海藻糖，二水海藻糖结构中的液态水再次转变为类固态水。这个温度范围内的多晶型转变似乎与二水海藻糖在保持蛋白质稳定性方面的生物保护作用相关。
