Topography of self-assembled zein structures on hydrophilic and hydrophobic surfaces

Introduction Zein, a major protein of corn, is conspicuous for its ability to form films. It is relatively hydrophobic, soluble in alcohol-water mixtures (40% 85%) but insoluble in pure water or alcohols. Current structural models of the zein molecule (Argos et al 1982, Matsushima et al 1997) consider zein is formed by nine to ten tandem repeats of α-helical segments aligned in anti-parallel fashion joined at each end by glutamine rich bridges. In Matsushima’s model, helical segments are aligned in a row forming a rectangular prism measuring 160Å x 46Å x 12Å. The front and back faces of the prism (160Å x 46Å) corresponding to the helix surfaces are considered hydrophobic, while the top and bottom faces (160Å x 12Å) containing the glutamine bridges are considered hydrophilic. This regular geometry allows zein to selfassemble into chains and layers or films. The structure of zein aggregates is affected by the environment polarity (Wang et al 2003).