The folded protein as a viscoelastic solid
Mechanical Properties, Folded State, Refolding Experiments
We apply a nanorheology technique to explore the mechanical properties of a globular protein in the frequency range 10 Hz–10 kHz and find that the folded state of the protein behaves like a viscoelastic solid. For increasing amplitude of the forcing, we observe three different regimes: linear elasticity, then a regime of viscoelastic but reversible deformations, and finally an irreversible regime. The second regime, which has the signature of a viscoelastic solid, gives access to the internal dissipation coefficient of the folded state, for which we find γ≈4×10− 5 kg/s, corresponding to an internal viscosity η~104 Pas for frequencies below ~10 Hz. We propose that the large discrepancy between this value, which agrees with previous AFM indentation experiments, and the value of the internal viscosity extracted from refolding experiments is a consequence of the viscoelastic nature of the protein's mechanics. Thus the present method yields detailed measurements of the mechanics of the folded state.
Wang, Y., & Zocchi, G. (2011). The folded protein as a viscoelastic solid. Physics Faculty Publications and Presentations., 96 (1), 18003. https://doi.org/https://doi.org/10.1209/0295-5075/96/18003