Chemical denaturation is a well-established approach for shifting the equilibrium between folded and unfolded states of globular proteins. However, as demonstrated for Ab1-42, when combined with isotopic enrichment and high-precision three-dimensional NMR experiments, the approach is also suitable for identifying small populations of transiently folded structural elements in disordered polypeptides. A very different approach to study the structural properties of a state that is not directly observable by NMR spectroscopy involves the use of high (2.5 kbar) hydrostatic pressure inside the NMR sample tube. Sudden application of high pressure can rapidly and reversibly shift the thermodynamic equilibrium between folded and disordered states of a peptide or protein. As demonstrated for Ab, such pressure-jump experiments then can probe structural properties of the NMR-invisible, misfolded oligomeric state by observing the transfer of magnetization to its disordered, NMR-visible state.