In Biological reactions, many intrinsically disorder proteins (IDPs) play crucial roles. Even though they do not behave as conformational proteins to have certain structures to select/interact with their substracts, their interactions in many pathways are dominated by altering dynamics, some even conformation changes, from disordered to order.
Since IDPs have no solid structures, their studies are restricted in crystal-related techniques. Although the NMR technique has no such restriction, the challenge of NMR is to have well-dispersion spectra to make sufficient resolution on chemical shift assignments. Nowadays, the development of NMR has successfully provided sufficient spectral resolution to offer unique opportunities for conformation and dynamics studies of IDPs. During the last few decades, NMR chemical shift, residual dipolar coupling (RDC), and hydrogen exchange rates are developed to evaluate local transient secondary structural elements with atomic resolution. Furthermore, paramagnetic relaxation enhancement (PRE) investigates long-range contacts.
In addition to those techniques in NMR, field-Cycling NMR spin relaxation study could intensively observe IDP dynamics due to its rapid correlation time. Low field relaxation brings more information on IDP than high-field spin relaxation. The relaxation dispersion curves of IDP could reveal dynamics correlation on dipolar mechanism because the measurable relaxation rate is comparably lower than structural proteins. However, the spectral resolution of the fixed-field relaxation study is restricted by the operating magnetic field. The High-field field-cycling NMR technique has broken this barrier of limited resolution in low-field spin relaxation study by applying a high-magnetic spectrometer as a "spectrum-resolution provider". Investigation IDP dynamics could definitely be benefited by such a high-field field-cycling NMR technique.