The hierarchical control of biogenic minerals from the morphology at the nanometer scale to subsequent assembly into macroscopic structures remains a major challenge. Although considerable efforts have been devoted to exploring effects of biomolecules in the biomineralization process, the studies to date are largely limited to atomic/molecular scale crystallization. Here it is shown how higher order structures of biomolecules exert critical effects on the long arrange assembly of biominerals for the example of platinum nanocubes aligned in 1D and 2D patterns. A Pt{100} specific peptide T7 (Ac-TLTTLTN-CONH2) adopts ST-turn conformations at low concentration in solution that supports the formation of cubic Pt nanocrystals and then spontaneously transforms these structures into β-sheets with increasing concentration. During this molecular assembly process the T7-Pt{100} specific interaction drives cubic Pt nanocrystal into large area and long range linear assembly along the [100] direction. We discuss the analysis of interactions between individual peptides to form long-range ordered structures in atomic-level detail by molecular dynamics simulation and their directional preferences of interaction with Pt nanocubes. The interaction energy with Pt (100) surfaces and facets is larger when peptide strands are parallel to the surface with side chains oriented flat-on to the surface rather than perpendicular. It is also found that docking of the Pt nanoparticles into 1D assemblies typically involves a 1.2 nm thick interlayer of water and a single T7 peptide in quasi ST-turn structure sandwiched between the nanoparticles. It is shown how small free energy differences on the scale a few kcal/mol support the observed directional assembly, help propose a mechanism to explain the formation of 1D and 2D ordered structures, and the reversibility of the process by changes in temperature or concentration. The findings, especially on the experimental side, mark a critical milestone in biomimetic material synthesis, and open vast opportunities for materials engineering with programmable structures from the atomic scale to the macroscopic scale.

Long range hierarchical assembly of Pt nanocrystals – Insights from measurements and molecular simulations of nanoparticle docking

256th National Meeting (2018)

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