Various types of restraints were tested to bias sampling. The use of restraints with respect to the initial model is a common approach for consistent refinement. Restraints keep structures close to their initial models, so that structure sampling can focus on finding the correct structure in the vicinity of the initial model. However, at the same time, restraints may hinder transitions between conformational states by raising the energy barriers for such transitions. As a result, structure sampling and refinement can become more difficult, especially when initial models deviate significantly from the native state. Previously, we introduced flat-bottom harmonic restraints applied to Cartesian coordinates of Cα atoms (Eq. 1).  