Rapid Interpretation\nof Protein Backbone Rotation\nDynamics Directly from Spin Relaxation Data

Besides their structure, dynamics is pivotal for protein\n functions,\nparticularly for intrinsically disordered proteins (IDPs) that do\nnot fold into a fixed 3D structure. However, the detection of protein\ndynamics is difficult for IDPs and other disordered biomolecules.\nNMR spin relaxation rates are sensitive to the rapid rotations of\nchemical bonds, but their interpretation is arduous for IDPs or molecular\nassemblies with a complex dynamic landscape. Here we demonstrate numerically\nthat the dynamics of a wide range of proteins, from short peptides\nto partially disordered proteins and peptides in micelles, can be\ncharacterized by calculating the total effective correlation times\nof protein backbone N–H bond rotations, τ<sub>eff</sub>, from experimentally measured transverse <sup>15</sup>N spin relaxation\nrates, <i>R</i><sub>2</sub>, using a linear relation. Our\nresults enable the determination of magnetic-field-independent and\nintuitively understandable parameters describing protein dynamics\nat different regions of the sequence directly from experiments. A\npractical advance of the approach is demonstrated by analyzing partially\ndisordered proteins in which rotations of disordered regions occur\nwith timescales of 1–2 ns, independent of their size, suggesting\nthat rotations of disordered and folded regions are uncoupled in these\nproteins.