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A Multi-Spectroscopic Investigation of Protein Structure in Biosilica Composites

Final Report Summary - BIOSILICA FORMATION (A Multi-Spectroscopic Investigation of Protein Structure in Biosilica Composites)

Proteins can fabricate hard and soft tissue. They sculpture the minerals in teeth and bone, shape cell membranes. While membrane proteins have been subject of significant research, the interaction of proteins with minerals are understudied. We know much less about the mechanisms involved in the formation of hydroxyapatide in teeth and bone and calcium carbonate in shells, mollusks and mussels. Within this project we have aimed at unraveling the molecular mechanisms involved in the silification of the cell walls of diatoms. These unicellular organisms are abundant in waters on earth and are the envy of material scientists because they can synthesize nanophase silica structures at room temperature in sea water ¬ – a process that takes material scientists extreme temperature and pHs. To better understand the fundamental principles behind the control proteins exert on biomineral structures, we chose to take a step forward and study simplified model peptides with reported control over mineral precipitation: a series of lysine-leucine peptides as well as a repeat unit of the diatom protein silafin. Our experiments based on sum frequency spectroscopy, solid state NMR, electron microscopy and simulations showed molecular details of the side chain-surface structure, interfacial folding and the resulting silica morphology in particles and nanometer thin films.