Proteins are highly flexible objects that perform their functions by sampling a wide range of conformations. The characterization of such motions is, therefore, crucial to establish the link between protein structure and function. In this project we will use advanced nuclear magnetic resonance in solution state and solid state to characterize functionally important motions in two challenging classes of proteins.The first target of these studies will be a large molecular chaperone of close to 1MDa in size. Conformational changes and dynamics are a prerequisite for the function of this assembly, as it binds, encloses and folds unfolded substrate proteins. Atomic-resolution structures of such large objects frozen in their crystal lattice do not provide access to dynamic information nor insight into the folding process itself. Here, we will exploit the complementary advantages of solid- and solution-state NMR spectroscopy to probe the dynamics, allostery and binding in a ≈1MDa object. Furthermore, we will study how the chaperone cage influences folding, by observing in real time and at atomic resolution how substrate proteins achieve their native fold inside and outside this large molecular edifice.We will furthermore study the mechanism of substrate translocation across membranes by characterizing structure, interactions and dynamics in a solute carrier protein. The dynamics of integral membrane proteins is currently poorly understood. This relates to the need to address membrane protein dynamics in an environment that closely resembles the native membrane. NMR techniques on proteoliposomes as well as nanodiscs are uniquely suited to get insight into native dynamics. We will use such techniques to relate the process of substrate translocation to inherent protein dynamics over a wide range of time scales. The development of novel NMR methods will be an integral part of these studies, and will allow us to probe protein motion at unprecedented detail.