Glassy dynamics and memory effects in an intrinsically disordered protein construct

Glassy, nonexponential relaxations in globular proteins are typically attributed to conformational behaviors that are missing from intrinsically disordered proteins. Yet, we show that single molecules of a disordered-protein construct display two signatures of glassy dynamics, logarithmic relaxations and a Kovacs memory effect, in response to changes in applied tension. We attribute this to the presence of multiple independent local structures in the chain, which we corroborate with a model that correctly predicts the force-dependence of the relaxation. The mechanism established here likely applies to other disordered proteins. Methods The data were collected using a custom-built magnetic tweezer as described in Ribeck et al. (2008) https://doi.org/10.1063/1.2981687. The force on each polymer was determined as described in Lansdorp et al. (2012) https://doi.org/10.1063/1.3687431.