The dissolution of collagen in ionic liquids (ILs) was highly dependent on the polarity of ILs, which was influenced by their sorts and concentrations. Herein, the solubility and dispersion degree of collagen in two sorts of ILs, namely 1-ethyl-methylimidazolium tetrafluoroborate ([EMIM][BF4]) with low polarity and 1-ethyl-3-methylimidazolium acetate ([EMIM][Ac]) with high polarity in a concentration range from 10% to 70% at 10 °C were investigated. When 150 mg of collagen was added to 30 mg of ILs, the minimum soluble collagen concentration was 0.02 mg/mL in 70% [EMIM][BF4] with lowest polarity and the maximum was 3.57 mg/mL in 70% [EMIM][Ac] with highest polarity, which indicates that soluble collagen and insoluble collagen fibers were both present. For insoluble collagens, differential scanning calorimetry showed that the thermal-stability was weakened when increasing the ILs concentration and polarity, and the fiber arrangement was looser with a more uniform lyophilized structure, observed by atomic force microscopy and scanning electron microscopy. For soluble collagens, electrophoresis patterns and Fourier transform infrared spectroscopy showed that no polypeptide chain degradation occurred during dissolution, but the thermal denaturation temperature decreased by 0.26 °C~ 7.63 °C with the increase of ILs concentrations, measured by ultra-sensitive differential scanning calorimetry. Moreover, the aggregation of collagen molecules was reduced when ILs polarity was increased as determined by fluorescence measurements and dynamic light scattering, which resulted in an increased loose fiber arrangement observed by atomic force microscopy. If the structural integrity of collagen needs to be retained, then the ILs sorts and concentrations should be considered.

中文翻译：

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小牛皮肤胶原蛋白在离子液体中的溶解度和分散度的研究

胶原在离子液体（ILs）中的溶解高度依赖于IL的极性，而极性受其种类和浓度影响。本文中，胶原在两种IL中的溶解度和分散度，即低极性的1-乙基-甲基咪唑四氟硼酸酯（[EMIM] [BF4]）和乙酸1-乙基-3-甲基咪唑鎓（[EMIM] [Ac]）研究了在10°C下浓度在10％至70％范围内的高极性电极。当将150 mg胶原蛋白添加到30 mg ILs中时，最小可溶性胶原蛋白浓度在70％[EMIM] [BF4]中为0.02 mg / mL，而极性最低，最大为3.57 mg / mL，在70％[EMIM] [ [Ac]具有最高极性，表明存在可溶性胶原蛋白和不溶性胶原蛋白纤维。对于不溶性胶原蛋白，差示扫描量热法显示，当增加ILs浓度和极性时，热稳定性会减弱，并且通过原子力显微镜和扫描电子显微镜观察，纤维排列较松散，冻干结构更均匀。对于可溶性胶原蛋白，电泳图谱和傅里叶变换红外光谱显示，在溶解过程中未发生多肽链降解，但随着ILs浓度的增加，热变性温度降低了0.26°C〜7.63°C（通过超灵敏差示扫描量热法测量） 。此外，通过荧光测量和动态光散射确定，当ILs极性增加时，胶原蛋白分子的聚集减少，这通过原子力显微镜观察到了增加的疏松纤维排列。如果需要保留胶原蛋白的结构完整性，则应考虑IL的分类和浓度。