The functionality of proteins is governed by the interplay between their structure and dynamics. Thus, understanding the mechanism and nature of protein motion is essential to understand their biological activity. Here we present and evaluate a novel method to study the basic and fundamental question concerning hierarchical protein motions. What are the dynamical modes of a protein, what is the interplay of these different modes, and how are they linked to the energy landscape of the protein? It is known that different motional modes are present simultaneously in the protein system. These motions occur at different time scales and at the same and/or different regions in the protein, while simultaneously influencing each other. All these motions can be described as thermally activated fluctuations. Nuclear spin relaxation parameters measured by nuclear magnetic resonance (NMR) are modulated primary by motions around the nuclear site. Thus, they are uniquely suited to study protein dynamics since it is possible to simultaneously gather information about different motional timescales and of different parts of the protein
