The detailed characterization of proteins is a key step toward the understanding of biological processes on a molecular level. The determination of their three-dimensional structures, which is central to such a characterization, can resolve many mechanistic questions related to function. However, this static picture of biology on a molecular level ignores the dynamic nature of living processes, which is necessary to perform the molecular function. NMR spectroscopy is exquisitely suited to probe the dynamics of biomolecules, because of its capability to deliver atomic-resolution information about the conformational space that a protein samples and the rates at which different conformational states interconvert. This accessibility to both structural and kinetic aspects of protein flexibility has indeed made solution-state NMR spectroscopy an important technique for the understanding of protein function. An important part of biology, however, is actually not occurring in the solution state: exciting systems of outstanding biological relevance such as membrane proteins or amyloid fibrils are very difficult – if at all – amenable to solution-state NMR. Solid-state NMR has seen great progress in the past decade, and the structure and local dynamics of immobilized proteins can now also be studied at atomic resolution. While this promises exciting new insight into the function of these molecules, it remains to establish the methodology that will allow to extract information about dynamics on different time scales in an accurate and reliable manner. The project presented here aims at developing new methods and improving existing methods for the quantification of motional amplitudes and time scales in solid-state proteins. A particular emphasis will be made on solid-state NMR methods that address protein dynamics in the time window of microseconds to seconds. This is a particularly interesting time scale where the function of many proteins occurs. The understanding of intrinsic protein dynamics in this regime can therefore provide important insight into protein function. The methods developed in this project will allow to study a wide range of biophysical processes. They will be applied here to two membrane proteins: the potassium channel KcsA and the mitochondrial ADP/ATP transporter. The foreseen results will shed light onto the molecular mechanisms of trans-membrane transport in these two proteins.