Paper BI+AS-MoM8
Protein Control of Materials Nucleation Probed by Sum Frequency Generation

Monday, November 7, 2016, 10:40 am, Room 101A

Proteins can act as Nature’s engineers at interfaces and manipulate both hard and soft tissue – they shape biominerals, manipulate cell membranes and nucleate materials. Despite the apparent importance for engineers working in the fields of surface engineering, drug delivery, or diagnostics, the molecular mechanisms dictating interfacial protein action have remained largely elusive. Our goal is to probe the structure and structural dynamics of such active proteins – in action at the surface.

Mineral proteins have the ability to control and steer the growth of hard tissue by binding specific mineral facets and precipitating silica and phosphates. They control the intricate mineral morphologies found in diatom cell walls, mollusk nacre, but also human teeth and bone. Inspired by diatom silification we used amphiphilic peptides consisting of leucine and lysine (LK peptides) to investigate biomineralization at surfaces. These peptides can adopt helical or beta sheet structures at the air-water interface. Upon addition of a silica precursor we obtained freestanding peptide-silica hybrid sheets with thicknesses of ~4 nm. We have followed the biomineral composition and interactions between peptides and silica at different early stages of biomineralization using a combination of surface spectroscopies and microscopies. Our experimental findings were complemented with molecular dynamics simulations. Our data shows that the peptide surface folding dictates the nanometer scale morphology of the prepared silica film.[1]

A particularly fascinating example of protein driven nucleation and phase transitions are ice-nucleating proteins. These proteins are used by specific bacteria to attack plants and cause frost damage by growing ice crystals at temperatures that would otherwise not allow ice formation. A recent survey by the NASA found large amounts of biological ice nucleators in the troposphere where they may affect global precipitation patterns. We have followed the interaction of freeze proteins with surrounding water molecules – how specialized protein sites lock water molecules in place and manipulate the flow of energy within the surrounding layers of water.[2]

1 H. Lutz, V. Jaeger, R. Berger, M. Bonn, J. Pfaendtner, T. Weidner

Biomimetic growth of ultrathin silica sheets using artificial amphiphilic peptides

Advanced Materials Interfaces, 1500282 (2015).

2 R. Pandey, K. Usui, R. A. Livingstone, S. A. Fischer, J. Pfaendtner, E. H. G. Backus, Y. Nagata, J. Fröhlich-Nowoisky, L. Schmüser, S. Mauri, J. F. Scheel, D. A. Knopf, U. Pöschl, M. Bonn, T. Weidner

Ice-nucleating bacteria control the order and dynamics of interfacial water

Science Advances, 2 (2016).