Direct Visualization of Orientation Competition in Protein Epitaxial Crystallization

ABSTRACT

The formation of two‐dimensional protein crystallites on solid surfaces is crucial in both natural biological processes and bottom‐up nanofabrication. However, direct molecular‐level insight into the dynamic evolution of epitaxial interfaces has remained challenging. Here, using in situ atomic force microscopy, we reveal the two‐dimensional crystallization dynamics of streptavidin on muscovite mica with single‐molecule resolution. We directly imaged the initial formation of multiple orientation domains during the crystallization process, a direct consequence of epitaxial matching to the three‐fold symmetry of the mica lattice. This metastable poly‐domain structure then evolves into a single‐oriented crystallite through two coexisting classical ripening pathways, i. e. Ostwald ripening and Smoluchowski‐type coalescence. The dominance of a single domain orientation arises from a competitive selection process during ripening, in which the initially largest domain ultimately consumes the neighboring domains of other orientations. Our work establishes a paradigm of domain coarsening in biomolecular epitaxy, providing a solid foundation for the rational design of functional bio‐nano interfaces.