Single-molecule techniques for probing the conformation, dynamics, and interactions of intrinsically disordered proteins

Intrinsically disordered proteins (IDPs) rely on inherent conformational dynamics to support vital cellular functions such as signaling and regulation. The heterogeneity of the conformational ensembles of IDPs poses a major challenge for classical biophysical techniques such as nuclear magnetic resonance, small-angle x-ray scattering, and circular dichroism, which measure ensemble-averaged properties and are unable to resolve the full range of substates sampled by IDPs or their interconversions. To address these limitations of ensemble-based methods, single-molecule techniques are essential to resolve the conformational heterogeneity and dynamics by continuously monitoring various properties of individual IDPs. In this review, we focus on the most commonly employed single-molecule techniques, briefly describe their methodologies, and highlight recent developments and applications of each technique toward the study of IDP structure, dynamics and interactions.