Conformational Motions of Disordered Proteins

Molecular dynamics in proteins animate and play a vital role for biologically relevant processes of these biomacromolecules. Quasielastic incoherent neutron scattering (QENS) is a well-suited experimental method to study protein dynamics from the picosecond to several nanoseconds and in the Ångström length-scale. In QENS experiments of protein solutions hydrogens act as reporters for the motions of methyl groups or amino acids to which they are bound. Neutron Spin-Echo spectroscopy (NSE) on the other hand offers the highest energy resolution in the field of neutron spectroscopy. It enables the study of slow collective motions in proteins up to several hundred nanoseconds and in the nanometre length-scale. In the following chapter I will present recent experimental studies that demonstrate the relevance of molecular dynamics for protein folding and for conformational transitions of intrinsically disordered proteins (IDPs). During the folding collapse the protein chain is exploring the accessible conformational space via molecular motions. A large flexibility of partially folded and unfolded proteins, therefore, is mandatory for rapid protein folding. IDPs on the other hand are a special case as they are largely unstructured under physiological conditions in their native states. A large flexibility of IDPs is a characteristic property of the proteins as it allows, for example, the interaction with various binding partners or the rapid response to different conditions.