Epitaxial Growth of Trichosanthin Protein Crystals on Mica Surface

We report the studies of epitaxial growth of trichosanthin (TCS) crystals on a mica substrate. TCS crystals grown on mica surface are found to be aligned well in four orientations, which was induced by the lattice of the mica substrate. The effect of potassium ions both at the mica surface and in solution was investigated by using different cation-modified surfaces and different precipitants. The results indicated that the binding of K+ ions on the mica surface played a critical role in the epitaxial crystal growth of TCS. The high-resolution structures of crystals grown in different precipitants were solved by synchrotron radiation X-ray crystallography, and the K+ binding sites in TCS crystals were identified. A strict lattice match between the TCS crystal and the mica substrate has been demonstrated based on the structural analysis of them. It reveals the mechanism of epitaxial nucleation and growth of TCS crystals. The experimental results provide new insights into the molecular mechanism of epitaxial...