摘要
cyclophilin A (CypA ) 的结构的稳定性用 H/D 交换和酰胺质子的化学移动的温度系数被调查，由 2D heteronuclear NMR 光谱学监视了。酰胺质子汇率被 H/D 交换实验为慢交换的质子测量并且海运测量了(溶剂暴露了酰胺) 为快交换的质子的 -HSQC 实验。化学移动的温度系数和酰胺质子的氢汇率与蛋白质结构显示出相当好的关联。完全， 44 仍然在 4 点在氢重氢交换的 86 d 从分配残余的 153 非脯氨酸存在吗？？
The structural stability of cyclophilin A （CypA） was investigated using H/D exchange and temperature coefficients of chemical shifts of amide protons, monitored by 213 heteronuclear NMR spectroscopy. Amide proton exchange rates were measured by H/D exchange experiments for slow-exchange protons and measured by SEA （Solvent Exposed Amides）-HSQC experiments for fast-exchange protons. Temperature coefficients of chemical shifts and hydrogen exchange rates of amide protons show reasonably good correlation with the protein structure. Totally, 44 out of 153 non-proline assigned residues still exist in 86 d of hydrogen-deuterium exchange at 4 ℃, suggesting that CypA structure should be highly stable. Residues in secondary structures of α2, β1, β2, β5, β6 and β7 might constitute the hydrophobic core of the protein. The change in free energy of unfolding （ △Gu^H2O ） of CypA was estimated to be （21.99± 1.53） kJ·mol^-1 by circular dichroism （CD）. The large free energy change is also an indicator of the high structural stability.
基金
Project supported by the Hundred Talent Project of Chinese Academy of Sciences and the National Natural Science Foundation of China （Nos 30470351, 30570352）.Acknowledgement The authors would like to thank Guo Hong-Xia and Cai Jian-Hua for their help in protein expression and purification.
