Polypeptide folding-mediated tuning of the optical and structural properties of gold nanoparticle assemblies.

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.

Observation of interference effects in coherent diffraction of nanocrystals under X-ray standing-wave illumination.

Coherent X-ray diffraction is a useful technique for understanding the structure of compact objects including those which can be represented as phase objects. X-rays are highly penetrating and have wavelengths very close to atomic spacing. In this work, gold nanocrystals (on a reflecting substrate) were imaged at the Advanced Photon Source and found to produce a novel double diffraction pattern.