Nanoscale Characterization of Zein Self-Assembly

Zein, a major protein of corn, is rich in alpha-helical structure. It has an amphiphilic character and is capable of self-assembly. Zein can self-assemble into various mesostructures that may find applications in food, agricultural, and biomedical engineering. Understanding the mechanism of zein self-assembly at the nanoscale is important for further development of zein structures. In this work, high-resolution transmission electron microscopy (TEM) images revealed nanosize zein stripes, rings, and discs containing a 0.35 nm periodicity, which is characteristic of beta-sheet. TEM images were interpreted in terms of the transformation of original alpha-helices into beta-sheet conformation after evaporation-induced self-assembly (EISA). The presence of beta-sheet was also detected by circular dichroism (CD) spectroscopy. Zein beta-sheets self-assembled into stripes, which curled into rings. Rings formed discs and eventually spheres. The formation of zein nanostructures was believed to be the result of beta-sheet orientation, alignment, and packing.