Positioning protein molecules on surfaces: a nanoengineering approach to supramolecular chemistry.

We discuss a nanoengineering approach for supramolecular chemistry and self assembly. The collective properties and biofunctionalities of molecular ensembles depend not only on individual molecular building blocks but also on organization at the molecular or nanoscopic level. Complementary to "bottom-up" approaches, which construct supramolecular ensembles by the design and synthesis of functionalized small molecular units or large molecular motifs, nanofabrication explores whether individual units, such as small molecular ligands, or large molecules, such as proteins, can be positioned with nanometer precision. The separation and local environment can be engineered to control subsequent intermolecular interactions. Feature sizes as small as 2 x 4 nm(2) (32 alkanethiol molecules) are produced. Proteins may be aligned along a 10-nm-wide line or within two-dimensional islands of desired geometry. These high-resolution engineering and imaging studies provide new and molecular-level insight into supramolecular chemistry and self-assembly processes in bioscience that are otherwise unobtainable, e.g., the influence of size, separation, orientation, and local environment of reaction sites. This nanofabrication methodology also offers a new strategy in construction of two- and three-dimensional supramolecular structures for cell, virus, and bacterial adhesion, as well as biomaterial and biodevice engineering.