Enzymes are dynamic systems able to explore many different conformations, and these dynamical properties are clearly connected to their biological function. Examples of this include allosteric regulation and product release, as well as the role of conformational selection in enzyme catalysis, 2-7 promiscuity 4 and evolution. In addition, such conformational dynamics can, in principle, be engineered in a targeted fashion to allow enzymes to acquire new catalytic functions and/or physiochemical properties. Understanding how enzymes manipulate and modulate conformational dynamics during both natural and directed evolution is an important step in this direction. In particular, understanding the dynamical behavior of decorating loops that cover enzyme active sites is important as such loops can regulate substrate selectivity, the evolution of new activities, and potentially also turnover rates. As such, targeting the dynamics of such active site loops is attractive from an engineering perspective, and therefore there is substantial interest in understanding loop dynamics and its impact on selectivity and catalysis.