Nanoparticles with flexible side chains cause peptides to adopt a helical form, making them promising anticancer agents.
Vincent Rotello and colleagues at the University of Massachusetts, Amherst, US, used functionalised gold nanoparticles to persuade a tetraaspartate peptide (TAP) to form an alpha-helix. In the absence of the nanoparticles, the peptide forms a random coil.
Ionic interactions between the ligands on the nanoparticle's surface, and the peptide in solution, cause the peptide to form a helix
In preliminary studies, Rotello and colleagues had used trimethylammonium functionalised gold nanoparticles to stabilise TAP into an alpha-helix. However, these particles were not biocompatible, limiting their potential applications. Now they have overcome this problem by using tetra(ethyl glycol) (TEG) ligands, which are biocompatible.
Lucia Pasquato, an expert in functional nanoparticles at the University of Trieste, Italy, explained that specific groups present on the surface of nanoparticles can induce a peptide to assume a particular conformation by ionic interactions.
Alpha-helices, common protein secondary structures, are involved in many protein-protein interactions. Some of these interactions take place in pathways critical in certain human diseases, such as cancer. By mimicking the alpha-helix of relevant proteins, it may be possible to create new cancer therapies.
Pasquato added, 'this is a first step towards the designing of more sophisticated artificial systems able to compete with nature in performing multivalent interactions for recognition processes.'