Two-dimensional (glyco)protein crystals as patterning elements for the controlled immobilization of functional molecules

One of the most suitable model systems for studying self-assembly and controlled molecular binding on a nanometer scale is that of crystalline bacterial surface layers, termed S-layers. Electron microscope studies have shown that S-layers form either oblique, trigonal, square or hexagonal lattices. S-layers are made of single (glyco)protein species with molecular weights in the range 40000-200000. S-layer proteins have shown the inherent ability to form mono- and double-layer self-assembly products in suspension and to recrystallize on solid supports. S-layers have revealed an unsurpassed high capacity for binding macromolecules in a regular fashion and maximum dense packing order. Chemical modification and activation procedures allow a specific adaptation of the S-layer surface for either electrostatic or covalent attachment of functional molecules such as enzymes or antibodies. The properties of S-layers as patterning elements in molecular nanotechnology are reviewed.