Self Assembling Organic Nanotubes

Abstract

Traditionally microscopic devices have been made by being cut or formed from larger objects, but as the dimensions of these products shrink below the micron level this process becomes increasingly difficult. Recently chemists have begun to try the opposite approach, that is building these nanoscale objects from molecular building blocks. Although these devices are too small to be manufactured by traditional materials science approaches, they are also far too large to be synthesized by classical chemical synthesis. In order to reach these nanoscale devices from a molecular level up, a massively convergent synthesis is required. Production of these nanoscale objects however, is not unknown and has been occurring for over three billion years in living biological systems. From microtubules to viruses, nature uses a broad variety of self-assembly techniques to build its sub-cellular machines that ultimately lead to life. Taking lessons from nature, we have designed and synthesized a number of self-assembling peptide based nanotubes. Nanotubes in general have recently attracted much attention, especially from carbon based nanotubes. Speculation on their utility range from molecular wires to catalysts to novel drug delivery systems. Peptide based nanotubes have many attractive features that make them a particularly good system to address these possibilities. For example, nanotubes based on cyclic peptides have easily alterable surface chemistries, adjustable internal diameters, open ends for including compounds such as metal or passing through ions and small molecules, and are also easily made by combining self-assembly with standard solid phase peptide synthesis. Furthermore, cyclic peptide based nanotubes have already been found to function as ion and small molecule membrane channels.