摘   要：
Proteins in solution are inherently dynamic, accessible to various conformations. These structural flexibilities include localized motions on the nanosecond timescales and inter-domain movements on the millisecond timescales. Most of our current understanding of protein dynamics comes from Nuclear Magnetic Resonance (NMR) experiments which cover picosecond to millisecond timescales. But the extent of the conformational change is usually not measureable by NMR or other ensemble-averaged techniques. A large number of proteins, moreover, are capable of large-amplitude conformational changes on the submillisecond to minute timescales—the timescales that overlap with those of function. The low-frequency conformational dynamics, though functionally important, have been elusive because it is impossible to synchronize proteins on this timescale to permit ensemble averaged studies. The single-molecule approach permits the direct monitoring of functionally important conformation transitions, and has allowed the discovery of such operation principles as dynamically induced fit, conformation gating, and local unfolding regulated conformational kinetics. Here, I discuss some recent results for a potentially clinically important example, human Insulin Degrading Enzyme (IDE, EC 3.4.24.56). The preliminary results from single-molecule Forster Resonance Energy Transfer (smFRET) indicate a previously unreported novel mode for conformational switches with many exciting implications in allosteric regulation as well as potential medical application.