Paper BI+AS+IPF+MN-MoA5
How Proteins Grow Calcium Carbonates – The Mechanism of Vaterite Bioprecipitation Studied at the Molecular Level by Sum Frequency Generation Spectroscopy

Monday, October 22, 2018, 2:40 pm, Room 101B

Proteins can act as Nature’s engineers at interfaces and manipulate hard tissue growths. Specialized peptides can bind and release specific mineral facets and grow the intricate mineral morphologies found in diatom cell walls, mollusk nacre, but also human teeth and bone. Taking clues from Nature we aim at understanding the mineralization processes at the molecular level and to develop design rules for biogenic nanophase materials. Mineral proteins control the biogenesis of CaCO₃ by selectively triggering the growth of calcite, aragonite or vaterite phases. The templating of CaCO₃ by proteins must occur predominantly at the protein/CaCO₃ interface. Surprisingly, molecular-level insights into the interface during active mineralization have been lacking. Here, we investigate the role of peptide folding and structural flexibility on the mineralization of CaCO₃. We discuss the mineral activity of amphiphilic peptides based on glutamic acid and leucine with ß-sheet and α-helical secondary structures. While both sequences lead to vaterite structures, the ßsheets yield free-standing vaterite nanosheet with superior stability and purity. Surface-specific spectroscopy studies and molecular dynamics simulations reveal that the interaction of calcium ions with the peptide monolayer restructures both the peptide backbone and side chains. This restructuring enables effective templating of vaterite by mimicry of the vaterite (001) crystal plane. The approach is universally applicable to mineral peptide engineering. We will discuss how analogous peptide designs can be used to steer the growth not only of calcium carbonates but also calcium oxalates.