The possible explanation is that there are two native conformations of DHFR.The difference of unfolding rate constants between these two species accounts for the two phases in kinetics study.

• 二氢叶酸还原酶去折叠过程中没有稳定存在的中间体，动力学过程中的两相可能是两种天然构象态的去折叠速度常数不同造成的。