Foyer-magazine : revue mensuelle

octobre 19361936/10 (A3)-1936/10.Appartient à l’ensemble documentaire : RhoneAlp

Adjusting the Metrics of 1‑D Helical Gold Nanoparticle Superstructures Using Multivalent Peptide Conjugates

The properties of nanoparticle superstructures depend on many factors, including the structural metrics of the nanoparticle superstructure (particle diameter, interparticle distances, etc.). Here, we introduce a family of gold-binding peptide conjugate molecules that can direct nanoparticle assembly, and we describe how these molecules can be systematically modified to adjust the structural metrics of linear double-helical nanoparticle superstructures. Twelve new peptide conjugates are prepared via linking a gold-binding peptide, AYSS­GAPP­MPPF (PEP_Au), to a hydrophobic aliphatic tail. The peptide conjugates have 1, 2, or 3 PEP_Au headgroups and a C₁₂, C₁₄, C₁₆, or C₁₈ aliphatic tail. The soft assembly of these peptide conjugates was studied using transmission electron microscopy (TEM), atomic force microscopy (AFM), and infrared (IR) spectroscopy. Several peptide conjugates assemble into 1-D twisted fibers having measurable structural parameters such as fiber width, thickness, and pitch that can be systematically varied by adjusting the aliphatic tail length and number of peptide headgroups. The linear soft assemblies serve as structural scaffolds for arranging gold nanoparticles into double-helical superstructures, which are examined via TEM. The pitch and interparticle distances of the gold nanoparticle double helices correspond to the underlying metrics of the peptide conjugate soft assemblies, illustrating that designed peptide conjugate molecules can be used to not only direct the assembly of gold nanoparticles but also control the metrics of the assembled structure

Structured DNA Aptamer Interactions with Gold Nanoparticles

DNA aptamers that bind biomolecular targets are of interest as the recognition element in colorimetric sensors based on gold nanoparticles (AuNP), where sensor functionality is related to changes in AuNP colloidal stability upon target binding. In order to understand the role of target binding on DNA–AuNP colloidal stability, we have used high-resolution NMR to characterize the interactions of the 36 nucleotide cocaine-binding aptamer (MN4) and related aptamers with AuNPs, cocaine, and cocaine metabolites. Changes in the aptamer imino proton NMR spectra with low (20 nM) concentrations of AuNP show that the aptamers undergo fast-exchange adsorption on the nanoparticle surface. An analysis of the spectral changes and the comparison with modified MN4 aptamers shows that the AuNP binding domain is localized on stem two of the three-stemmed aptamer. The identification of an AuNP recognition domain allows for the incorporation of AuNP binding functionality into a wide variety of aptamers. AuNP-induced spectral changes are not observed for the aptamer–AuNP mixtures in the presence of cocaine, demonstrating that aptamer absorption on the AuNP surface is modulated by aptamer–target interactions. The data also show that the DNA–AuNP interactions and sensor functionality are critically dependent on aptamer folding