pH-induced changes in intrinsically disordered proteins.

Intrinsically disordered proteins are typically enriched in amino acids that confer a relatively high net charge to the protein, which is an important factor leading to the lack of a compact structure. There are many different approaches that can be used to experimentally confirm whether a protein is intrinsically disordered. One such approach takes advantage of the distinctive amino acid composition to test whether a protein is a genuine IDP. In particular, the conformation of the protein can be monitored at different pHs; as opposed to globular or ordered proteins, IDPs will typically gain structure under highly acidic or basic conditions. Here, we describe circular dichroism and fluorescence spectroscopic experimental approaches in which the conformation of proteins is monitored as pH is altered as a way of testing whether the protein behaves as an intrinsically disordered protein.