Shuai Zhang1 Harley Pyles2 David Baker2 James De Yoreo1

1, Pacific Northwest National Lab, Richland, Washington, United States
2, University of Washington, Seattle, Washington, United States

In nature, protein molecules can self-assembly into 2D crystalline arrays on templates like, cell wall and membrane. The created protein matrixes, like bacterial S-layer and purple membrane, can have unique structure and biological function. Protein self-assembly structures have also been synthesized artificially on solid-liquid interface to fulfill certain applications, like energy conversion. However the general model to describe the self-assembly process of protein at solid-liquid crystal is still missing. It can be the potential obstacle for designing and applications of protein 2D matrix in future.
In this project, we used the designed helical repeat protein (DHR10-micaX) [1] as the model to elucidate entropy-driven effect to the dynamic and final self-assembly structure of protein at solid-liquid interface of mica via high-speed atomic force microscopy (AFM). After carefully selection of cations and subsequent changes of the amount at interface, DHR10-micaX with size in nanometer can form 2D crystal across area of million times of their length with unique orientation. This class of protein can also form nanowire arrays with uniform orientation, if the protein-protein interaction is tuned. Combining in-situ data of high-speed AFM and simulation, we elucidated the role of entropy in the whole process, and we also discussed the effect of hydration layer to protein dynamics at solid-liquid interface.

1. Brunette, T.J., et al., Exploring the repeat protein universe through computational protein design. Nature, 2015. 528(7583): p. 580-584.