안준영 (POSTECH)

서종철 (POSTECH)

안준영 (POSTECH)

임다혜 (POSTECH)

김민수 (POSTECH)

서종철 (POSTECH)

 Characterizing intrinsically disordered regions (IDRs) in proteins is essential for understanding cell regulation and disease mechanisms, yet remains analytically challenging. In this study, we present the mass spectrometry-based strategy that leverages the high interfacial affinity of iodide ions to assess protein chain disorder directly in solution.

 During native electrospray ionization (ESI) in NH₄I buffer, well-structured proteins naturally capture multiple iodide adducts, appearing as low-charge ions with distinct adduct footprints. In contrast, under denaturing acidic conditions or when analyzing intrinsically disordered proteins (IDPs) at neutral pH, iodide binding is virtually absent. Molecular dynamics simulations confirm that iodide selectively enriches at the solvent-exposed surfaces of structured domains, but avoids highly flexible, disordered chains.

 By simply counting iodide adducts via mass spectrometry, we can easily distinguish disordered regions from structured domains. Combined with complementary tools like ion mobility spectrometry (IMS), this iodide-adduct profiling offers a straightforward, high-throughput approach to monitor order-disorder transitions, folding intermediates, and domain stability in solution.