Rational design of peptide-based building blocks for nanoscience and synthetic biology Craig T. Armstrong, a Aimee L. Boyle, a Elizabeth H. C. Bromley, a Zahra N. Mahmoud, a Lisa Smith, a Andrew R. Thomson a and Derek N. Woolfson * ab Received 28th January 2009, Accepted 23rd March 2009 First published as an Advance Article on the web ????? DOI: 10.1039/b901610d The rational design of peptides that fold to form discrete nanoscale objects, and/ or self-assemble into nanostructured materials is an exciting challenge. Such efforts test and extend our understanding of sequence-to-structure relationships in proteins, and potentially provide materials for applications in bionanotechnology. Over the past decade or so, rules for the folding and assembly of one particular protein-structure motif—the a-helical coiled coil— have advanced sufficiently to allow the confident design of novel peptides that fold to prescribed structures. Coiled coils are based on interacting a-helices, and guide and cement many protein–protein interactions in nature. As such, they present excellent starting points for building complex objects and materials that span the nano-to-micron scales from the bottom up. Along with others, we have translated and extended our understanding of coiled-coil folding and assembly to develop novel peptide-based biomaterials. Herein, we outline briefly the rules for the folding and assembly of coiled-coil motifs, and describe how we have used them in de novo design of discrete nanoscale objects and soft synthetic biomaterials. Moreover, we describe how the approach can be extended to other small, independently folded protein motifs—such as zinc fingers and EF-hands— that could be incorporated into more complex, multi-component synthetic systems and new hybrid and responsive biomaterials. 1. Introduction Nature provides considerable inspiration for what might be achieved through self- assembly in water. It uses lipids, nucleic acids, carbohydrates and polypeptides as building blocks for self-assembling systems, though nucleic acids and polypeptides form the best-defined biosupramolecular (tertiary and quaternary) structures. 1 Taking such inspiration, nanoscientists and synthetic biologists are achieving much in synthetic self-assembly using nucleic-acid building blocks. 2,3 Arguably, however, polypeptides present better long-term building materials as they form more-diverse examples of self-assembled structures and functions in biology; they are stable, or can be stabilised over a broad range of conditions; and they can be produced in large quantities from renewable sources using recombinant DNA tech- nologies and gene expression in a variety of hosts. For these reasons, we have adop- ted Nature’s favoured macromolecules and use peptides and proteins to design and a School of Chemistry, University of Bristol, Bristol, UK BS8 1TS. E-mail: D.N.Woolfson@ bristol.ac.uk b Department of Biochemistry, University of Bristol, Bristol, UK BS8 1TD ART  B901610D PAPER 143/19 www.rsc.org/faraday_d | Faraday Discussions 1 5 10 15 20 25 30 35 40 45 50 55 This journal is ª The Royal Society of Chemistry 2009 Faraday Discuss., 2009, 143, 1–13 | 1