Protein Nanotechnology

by Jonathan Trent

In support of NASA’s efforts to make missions "faster, better, and cheaper" there is a growing need for the development of smaller, stronger, and ‘smarter’ scientific probes compatible with space exploration. The necessary breakthroughs in this area may well be achieved in the revolutionary field of nanotechnology. This is technology on the scale of molecules, which holds the promise of creating devices smaller and more efficient than anything currently available. While a great deal of exciting research is developing around carbon nanotubes-based nanotechnology, we at NASA Ames Research Center are also exploring biologically inspired nanotechnology.

The biological ‘unit,’ the living cell, may be considered the ultimate nano-scale device. Cells, which are constructed of nano-scale components, are extremely sensitive, highly efficient environmental sensors capable of rapid self-assembly, flawless self-repair, and adaptive self improvement; not to mention their potential for nearly unlimited self-replicate. Ames is focusing on a major component of all cells (proteins) that are capable of self-assembling into highly ordered structures. A protein known as HSP60 is currently being studied that spontaneously forms nano-scale ring structures (Fig. 1A, end view; B, side view), which can be induced to form chains (Fig. 1C) or filaments (Fig. 1D).

By using thermostable HSP60s, highly efficient methods have been developed for purifying large quantities of these proteins and by using the ‘tools’ of molecular biology, their composition and structure-forming capabilities are being currently modified.

For example, by removing a small fragment of the HSP60 protein, protein rings are produced that do not form chains or filaments, but continue to form rings that spontaneously assemble into highly ordered hexagonally-packed arrays (Fig. 2A).

By further modifying each of these proteins so they bind metal atoms, these proteins can be used as a template to create an ordered pattern of metal on a surface with nanometer spacing. Ultimately the hope is to use such ordered arrays of metal to manufacture nano-scale electronic devices. Similarly, metal binding to proteins that form filaments (Fig. 2B) may be used to create self-assembling nano-scale wires, which may someday be used to produce self-assembling circuits.

There are many potential applications for protein-based nanotechnology applicable to the production of smaller, stronger, and ‘smarter’ probes for NASA or more generally for applications in electronics and medicine. The combination of nanotechnology, information technology, and biotechnology at NASA Ames Research Center provides an excellent research environment for biologically-inspired nanotechnology. Analytical capabilities in nanotechology provide essential tools for determining structure and function of protein-based systems. Supercomputing in information sciences provide capabilities essential for molecular simulations and biomolecule visualizations. Biotechn ology provides the methodological basis for the genetic engineering essential for modifying and functionalizing protein structures. The goal is to establish the feasibility of creating useful protein-based nanostructures with applications for NASA and other critical areas of technology.

Figure 1: Protein rings (A end view, and B side view), chains of rings (C), and bundles of chains (D) that can be used in nanotechnology.

Fig. 2: Modified proteins form hexagonally packed rings (A) or metal-containing protein filaments (B).