Scaling behaviors of α-zein in acetic acid solutions

Whether the concentration scaling behavior of a protein solution is similar to that of neutral polymer solutions, polyelectrolyte solutions, or neither still remains unclear. In this paper, the structure and rheological properties of α-zein in acetic acid solutions have been investigated by small-angle X-ray scattering (SAXS), rheology, and circular dichroism (CD) measurements. Through the investigation of the radii of gyration, the secondary structure, and the solution viscosities of α-zein in acetic acid solutions as a function of α-zein concentration, we observed two distinct scaling regions with an identical threshold. This critical concentration is close to the bulk density of the α-zein in very dilute solution. The scaling relationships are close to the theoretical predictions for polyelectrolyte solutions, but obvious discrepancies still exist. The phenomena presented here may be widely present in other protein solutions, which can stimulate more attentions on the understanding of the scaling behaviors of protein solutions.