A molecular sphere assembled from 12 metal ions and 24 organic ligands is lined with amino acids to generate chiral cavities reminiscent of those found in enzymes
Enzymes, which are made up of amino acids, catalyse chemical transformations by providing a reaction pathway that is lower in energy than those through which they usually proceed. Critical to this ability are the presence of so-called active sites — well-defined pockets in the enzyme structure that bind substrates and subsequently mediate their conversion into products with a high degree of specificity. Making artificial enzyme mimics is not straightforward, but with a modular self-assembly process, researchers in Japan have made hollow nanocages with inner chiral cavities.
Makoto Fujita and co-workers1 have developed a strategy to make spherical nanostructures using palladium ions to link 24 bent organic building blocks (ligands) into a hollow cage approximately 4 nm in diameter. By attaching an amino acid or a short peptide chain to the concave side of the curved ligand, nanospheres are formed with internal cavities that are lined with these chiral groups. This robust assembly process is demonstrated for a range of amino-acid modified ligands, and these can be mixed together in one pot to produce a variety of spheres with different chiral cavities.
Although the mixed assembly process is statistical in nature, it is also reversible, which suggests that a template could be used to bias the system to favour just one (or a few) specific cavities. Ultimately, it is hoped that these nanospheres could be evolved to produce functional artificial enzyme pockets.
Suzuki, K. Kawano, M. Sato, S. & Fujita, M. Endohedral peptide lining of a self-assembled molecular sphere to generate chirality-confined hollows. J. Am. Chem. Soc. 10.1021/ja073629b (2007).
About this article
Cite this article
Cantrill, S. An inside job. Nature Nanotech (2007). https://doi.org/10.1038/nnano.2007.296