Atomistic Structure of Monomolecular Surface Layer Self-Assemblies: Toward Functionalized Nanostructures

The concept of self assembly is one of the most promising strategies for the creation of defined nanostructures and therefore became an essential part of nanotechnology, for the controlled bottom-up design of nano scale structures. Surface layers (S-layers), which represent the cell envelope of a great variety of prokaryotic cells, show outstanding self-assembly features in vitro and have been successfully used is the basic matrix for molecular construction kits. Here we present the three-dimensional structure of an S-layer lattice based on tetrameric unit cells, which will help to facilitate the directed binding of various molecules on the S-layer lattice, thereby creating functional nanoarrays for applications in nanobiotechnology. Our work demonstrates the successful combination of computer simulations, electron microscopy (TEM), and small-angle X-ray scattering (SAXS) as a tool for the investigation of the structure of self-assembling or aggregating proteins, which cannot be determined by X-ray crystallography. To the best of our knowledge, this is the first structural model at an amino acid level of an S-layer unit cell that exhibits p4 lattice symmetry.