本研究探讨了在模拟小肠末端环境下酪蛋白磷酸肽（β-casein phosphopeptides(1-25)，简称CPP）与不同钙盐的相互作用情况。实验以等温滴定量热仪为方法，以热力学参数、化学计量数及亲和力常数为指标，评价不同钙盐与CPP的相互作用情况。结果表明，CPP与不同钙盐两两相互作用，且均为由熵驱动的自发反应（pH 8.0，37 ℃），该反应的主要推动力为离子相互作用力。不同钙盐与CPP反应时，焓变，熵变及自由能无明显差别（p>0.05），而化学计量数和亲和力常数存在显著性差异（p<0.05）。CPP与葡萄糖酸钙，乳酸钙和氯化钙相互作用时，化学计量数较高（3~4 mol/mol），而与天冬氨酸钙结合的化学计量数较低（2~3 mol/mol）。此外，相比其他钙盐，乳酸钙与CPP结合的亲和力常数最低。多肽与钙盐结合数高且亲和力较低时有利于小肠对钙的吸收。因此，相对于其他钙盐，CPP与乳酸钙结合可能更有利于小肠对钙的吸收。本研究为更好地了解CPP与不同钙盐溶液在模拟小肠末端环境下的热力学变化及结合情况奠定坚实的基础。

In this study, the interactions between β-casein phosphopeptides (1-25) (CPP) and different calcium salts were investigated in the simulated small intestine terminal environment were investigated. Isothermal titration calorimetry (ITC) was used as the analysis method, and thermodynamic parameters, stoichiometric number and affinity constants were used as indicators to evaluate the interactions between different calcium salts and CPP. The results showed that CPP could interact with different calcium salts, and both were spontaneous reactions driven by entropy (pH 8.0, 37 ℃). The main driving force of this reaction was ionic interactive forces. When different calcium salts reacted with CPP, there was no obvious difference in enthalpy change, entropy change and free energy (p>0.05), but there were significant differences in stoichiometric number and affinity constants (p<0.05). The stoichiometric number was higher (3~4) when CPP interacted with calcium gluconate, calcium lactate or calcium chloride, whilst the stoichiometric number was lower (2~3) when CPP interacted with calcium aspartate. In addition, compared with other calcium salts, calcium lactate had the lowest affinity constant for its binding to CPP. A higher number of calcium salt binding to the peptide and a lower binding affinity were beneficial to the absorption of calcium in the small intestine. Therefore, compared with other calcium salts, the binding of CPP with calcium lactate may be more conducive to the absorption of calcium in the small intestine. This study lays a solid foundation for better understanding of the thermodynamic changes and interactions of CPP with different calcium salts in the environment simulating that of the small intestine.

国家自然科学基金项目（3197160311）；广东省创新创业团队项目（2019ZT08N291）