%0 Journal Article %A Aili, Daniel %A Gryko, Piotr %A Sepulveda, Borja %A A. G. Dick, John %A Kirby, Nigel %A Heenan, Richard %A Baltzer, Lars %A Liedberg, Bo %A Ryan, Mary P. %A Stevens, Molly M. %D 2011 %T Polypeptide Folding-Mediated Tuning of the Optical and Structural Properties of Gold Nanoparticle Assemblies %U https://acs.figshare.com/articles/journal_contribution/Polypeptide_Folding_Mediated_Tuning_of_the_Optical_and_Structural_Properties_of_Gold_Nanoparticle_Assemblies/2572714 %R 10.1021/nl203559s.s001 %2 https://acs.figshare.com/ndownloader/files/4215931 %K assembly properties %K tissue engineering %K particles form %K Gold Nanoparticle AssembliesResponsive %K UV %K particle mobility %K Structural Properties %K particle aggregation dynamics %K particle size %K nonlinear polypeptide %K drug delivery %X Responsive hybrid nanomaterials with well-defined properties are of significant interest for the development of biosensors with additional applications in tissue engineering and drug delivery. Here, we present a detailed characterization using UV–vis spectroscopy and small angle X-ray scattering of a hybrid material comprised of polypeptide-decorated gold nanoparticles with highly controllable assembly properties. The assembly is triggered by a folding-dependent bridging of the particles mediated by the heteroassociation of immobilized helix–loop–helix polypeptides and a complementary nonlinear polypeptide present in solution. The polypeptides are de novo designed to associate and fold into a heterotrimeric complex comprised of two disulfide-linked four-helix bundles. The particles form structured assemblies with a highly defined interparticle gap (4.8 ± 0.4 nm) that correlates to the size of the folded polypeptides. Transitions in particle aggregation dynamics, mass-fractal dimensions and ordering, as a function of particle size and the concentration of the bridging polypeptide, are observed; these have significant effects on the optical properties of the assemblies. The assembly and ordering of the particles are highly complex processes that are affected by a large number of variables including the number of polypeptides bridging the particles and the particle mobility within the aggregates. A fundamental understanding of these processes is of paramount interest for the development of novel hybrid nanomaterials with tunable structural and optical properties and for the optimization of nanoparticle-based colorimetric biodetection strategies. %I ACS Publications