Short-Time Glassy Dynamics in Viscous Protein Solutions with Competing Interactions

The glass transition of colloidal dispersions interacting with both a short-ranged attraction and long-ranged repulsion is studied using highly purified lysozyme solutions. Newtonian liquid behavior is observed at all conditions while measurements of the dynamics in the short-time limit show features typical of glassy colloidal systems at high protein concentrations. This interesting behavior is due to the competition of the attraction and repulsion that produces a heterogeneous microstructure only at intermediate range length scales. The results demonstrate that theories for the macroscopic properties of systems with competing interactions need to include intermediate range order.

Figure 1

(a) Specific viscosities (symbols) in the zero-shear limit are plotted as a function of protein volume fraction at three temperatures relative to HS predictions (line) [33]. (b) Solution viscosities are plotted as a function of the shear rate for selected volume fractions.

Figure 2

The normalized mean squared displacement of lysozyme samples at short-time (filled symbols) and long-time (open symbols) are plotted as a function of normalized time. Also shown are previous results for a system with micrometer sized colloidal particles (lines) [4] representative of fluid, cluster, glassy, and gel states. Error bars represent one standard deviation.

Figure 3

The specific viscosity of lysozyme is plotted as a function of short-time self-diffusivity (symbols) relative to calculations for HS fluids (solid line).

Figure 4

Structure factors obtained from SANS are plotted for several sample conditions, indicating the formation of IRO peaks at the same $q$ value ($q_{\mathrm{IRO}}$) shown by the dotted line.