title: Peptide-Directed Assembly of Single-Helical Gold Nanoparticle Superstructures Exhibiting Intense Chiroptical Activity.
abstract: Chiral nanoparticle assemblies are an interesting class of materials whose chiroptical properties make them attractive for a variety of applications. Here, C18-(PEPAuM-ox)2(PEPAuM-ox= AYSSGAPPMoxPPF) is shown to direct the assembly of single-helical gold nanoparticle superstructures that exhibit exceptionally strong chiroptical activity at the plasmon frequency with absolute g-factor values up to 0.04. Transmission electron microscopy (TEM) and cryogenic electron tomography (cryo-ET) results indicate that the single helices have a periodic pitch of approximately 100 nm and consist of oblong gold nanoparticles. The morphology and assembled structure of C18-(PEPAuM-ox)2are studied using TEM, atomic force microscopy (AFM), Fourier transform infrared (FTIR) spectroscopy, circular dichroism (CD) spectroscopy, X-ray diffraction (XRD), and solid-state nuclear magnetic resonance (ssNMR) spectroscopy. TEM and AFM reveal that C18-(PEPAuM-ox)2assembles into linear amyloid-like 1D helical ribbons having structural parameters that correlate to those of the single-helical gold nanoparticle superstructures. FTIR, CD, XRD, and ssNMR indicate the presence of cross-β and polyproline II secondary structures. A molecular assembly model is presented that takes into account all experimental observations and that supports the single-helical nanoparticle assembly architecture. This model provides the basis for the design of future nanoparticle assemblies having programmable structures and properties.
authors.affiliation: Department of Chemistry, University of Pittsburgh , 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Andrea D
authors.initials: AD
authors.lastname: Merg
authors.affiliation: Department of Structural Biology, School of Medicine, University of Pittsburgh , 3501 Fifth Avenue, Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Boatz
authors.affiliation: Department of Structural Biology, School of Medicine, University of Pittsburgh , 3501 Fifth Avenue, Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Mandal
authors.affiliation: Department of Structural Biology, School of Medicine, University of Pittsburgh , 3501 Fifth Avenue, Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Gongpu
authors.initials: G
authors.lastname: Zhao
authors.affiliation: Department of Chemistry, University of Pittsburgh , 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Soumitra
authors.initials: S
authors.lastname: Mokashi-Punekar
authors.affiliation: Department of Chemistry, University of Pittsburgh , 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Chong
authors.initials: C
authors.lastname: Liu
authors.affiliation: Department of Structural Biology, School of Medicine, University of Pittsburgh , 3501 Fifth Avenue, Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Xianting
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Structural Biology, School of Medicine, University of Pittsburgh , 3501 Fifth Avenue, Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Peijun
authors.initials: P
authors.lastname: Zhang
authors.affiliation: Department of Structural Biology, School of Medicine, University of Pittsburgh , 3501 Fifth Avenue, Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Patrick C A
authors.initials: PCA
authors.lastname: van der Wel
authors.affiliation: Department of Chemistry, University of Pittsburgh , 219 Parkman Avenue, Pittsburgh, Pennsylvania 15260, United States.
authors.forename: Nathaniel L
authors.initials: NL
authors.lastname: Rosi