Self-Assembly Behavior of Zein on Two Different Substrates Visualized by Atomic Force Microscopy

When protein molecules come into contact with different types of substrate materials, the surface properties of the substrate will have a significant effect on their self-assembly behavior. The purpose of this study was to investigate the self-assembly behavior of zein molecules on the two different substrates. Herein, the microstructure of zein molecules on the surface of two typical substrates, mica and glass, were characterized in detail by atomic force microscopy. It was found that zein molecules self-assemble to form spherical structures with uniform size and close arrangement on mica substrates. Compared with mica, the rough glass surface possesses a larger water contact angle, which leads to weaker interaction between zein molecules and its surface, thus enhancing the interaction between zein molecules. Therefore, the zein molecules on the glass substrate exhibit a distinct hierarchical arrangement of one large globule surrounded by many smaller ones. This work provides valuable information for further study of the self-assembly behavior of zein molecules on the substrate surface.