Short-Time Glassy Dynamics in Viscous Protein Solutions with Competing Interactions
P. Douglas Godfrin, Steven Hudson, Kunlun Hong, Lionel Porcar, Peter Falus, Norman J. Wagner, Yun Liu
Although there have been numerous investigations of the glass transition for colloidal dispersions with only a short range attraction (SA), less is understood for systems interacting with a SA and an additional longer range repulsion (LR), which is ubiquitous in aqueous protein solutions at low ionic strength. Newtonian liquid behavior is observed at all concentrations, even up to 480 mg/mL, where the zero shear viscosity increases by more than three orders of magnitude with increasing concentration at certain temperatures. Remarkably, despite this macroscopic liquid-like behavior, the diffusion in the short-time limit shows features typical of glassy colloidal systems. The investigation of the inter-protein structure indicates that a heterogeneous density distribution produces localized regions of high density that reduce protein motion in the short-time limit. This heterogeneous density distribution occurs only at the intermediate range length scale driven by the competing potential features and is distinct from commonly studied colloidal gel systems where the heterogeneous density distribution tends to extend to the whole system. The presence of the long-range repulsion also allows for more mobility over large length and long time scales resulting in the macroscopic relaxations of the structure. The experimental results provide evidence for the need to explicitly include the intermediate range order in theories for the macroscopic properties of protein solutions interacting via SALR potentials.
glass transition, intermediate range order, protein, viscosity
, Hudson, S.
, Hong, K.
, Porcar, L.
, Falus, P.
, Wagner, N.
and Liu, Y.
Short-Time Glassy Dynamics in Viscous Protein Solutions with Competing Interactions, Physical Review Letters, [online], https://doi.org/10.1103/PhysRevLett.115.228302, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=918754
(Accessed December 6, 2023)