Proteins are generally thought to adopt unique structures determined by their amino acid sequences, as outlined by Anfinsen's dogma.However, proteins are not strictly static objects, but rather populate ensembles of (sometimes similar) conformations.Transitions between these states occur on a variety of length scales (tenths of Å to nm) and time scales (ns to s), and have been linked to functionally relevant phenomena such as allosteric signaling and enzyme catalysis.The study of protein dynamics is most directly concerned with the transitions between these states, but can also involve the nature and equilibrium populations of the states themselves.These two perspectives—kinetics and thermodynamics, respectively—can be conceptually synthesized in an "energy landscape" paradigm:highly populated states and the kinetics of transitions between them can be described by the depths of energy wells and the heights of energy barriers, respectively.