Chiral gold nanoparticle superstructures have attracted much interest because of their potential applications in sensing and opto-electronics. Peptide-based methods for controlling the structure of chiral gold nanoparticle single helices have been developed. These methods employ peptide conjugate molecules, composed of a gold-binding peptide (PEPAu = AYSSGAPPMoxPPF) attached to an aliphatic tail with varying lengths (C16-C22); these constructs associate with nanoparticles and direct their assembly into single helices ranging in helical pitch from 80-120 nm, respectively. In this work, we study the effect of peptide backbone modification on gold nanoparticle assembly for conjugates with low self-assembly propensity. We prepare a series of peptide conjugate molecules, C14-(AYSXGAPPMoxPPF)2 (X = S, T, V, and F), which differ in their relative hydrophobicity. We employ FTIR and CD spectroscopy to study peptide conjugate assembly propensity as a function of backbone modification. Using AFM and X-ray diffraction, we examine the important morphological differences in soft assembly that arise from backbone modification. We identify specific amino acid modifications that allow for the assembly of chiral gold nanoparticle single helices with short pitch length. We determine that the structure of the final nanoparticle assembly can be directly correlated to the peptide conjugate assembly. Importantly, we show that systematic single amino acid modification can be used to not only induce the assembly of gold nanoparticles but also to alter their optical properties.

Effects of peptide backbone modification on the assembly, structure, and properties of chiral gold nanoparticle single helices

255th National Meeting (2018)

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