Physical state of L-histidine after freeze-drying and long-term storage
Physical state of L-histidine after freeze-drying and long-term storage
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DOI：
10.1016/s0928-0987(99)00028-7
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发表时间：
1999-08-01
影响因子：
4.6
通讯作者：
Wadsten, T
中科院分区：
文献类型：
--
作者：
Österberg, T;Wadsten, T
通过差示扫描量热法分析了不同 pH 值并与盐、金属离子、聚山梨酯 80 和蔗糖混合的 L-组氨酸液体样品，以评估这些添加剂在冷冻和解冻过程中对 L-组氨酸玻璃化转变温度和结晶的影响。将不同 pH 值的 L-组氨酸溶液在热循环和不热循环下进行冷冻干燥，并通过粉末 X 射线衍射研究长期储存后冻干饼的物理状态。无定形 L-组氨酸在暴露于湿气时会结晶，并报告了结晶材料的特性。 L-组氨酸在冷冻和解冻过程中的结晶取决于溶液的 pH 值，并且在 pH 6 时结晶程度最低，这与咪唑啉功能的 pK(a) 一致。蔗糖在解冻过程中抑制 L-组氨酸的结晶，而氯化钠或聚山梨酯 80 则不然。添加高达 10% (w/w) 的金属离子（Ca2+ 和 Mg2+）并没有显着降低玻璃化转变温度，而添加 Zn2+ 则提高了玻璃化转变温度。冷冻干燥后 L-组氨酸的物理状态取决于溶液的 pH 值和冷冻周期。如果冻干材料不受潮，则无定形 L-组氨酸结晶的风险较低。 (C) 1999 年由 Elsevier Science B.V. 出版。保留所有权利。
Liquid samples of L-histidine of varying pH values and mixed with salt, metal ions, polysorbate 80 and sucrose have been analysed by differential scanning calorimetry to evaluate the influence of these additives on the glass transition temperature and crystallisation of L-histidine during freezing and thawing. L-Histidine solutions of varying pH were freeze-dried with and without a thermal cycle and the physical state of the freeze-dried cakes, following long-term storage, were studied by powder X-ray diffraction. Amorphous L-histidine crystallised when it was exposed to moisture, and the identity of the crystalline materials is reported. The crystallisation of L-histidine during freezing and thawing is dependent on the pH of the solution and is shown to be at a minimum at pH 6, which coincides with the pK(a) of the imidazoline function. Sucrose inhibited the crystallisation of L-histidine during thawing, while sodium chloride or polysorbate 80 did not. The addition of metal ions (Ca2+ and Mg2+) up to 10% (w/w) did not depress the glass transition temperature significantly, while the addition of Zn2+ increased it. The physical state of L-histidine after freeze-drying is shown to be dependent on both the pH of the solution and the freezing cycle. The risk of crystallisation of amorphous L-histidine is low if the freeze-dried material is protected from moisture. (C) 1999 Published by Elsevier Science B.V. All rights reserved.