Peptide-based methods
have proven useful for constructing helical
gold nanoparticle superstructures that exhibit strong plasmonic chiroptical
activity. Superstructure syntheses using the amphiphilic peptide conjugate
C16-(AYSSGAPPMoxPPF)2typically yield
1D helices with a broad length distribution. In this study, we introduce
a molecular modulator approach for controlling helix length. It represents
a first step toward achieving narrowly disperse populations of single
helices fabricated using peptide-based methods. Varying amounts of
modulator, C16-(AYSSGA)2, were added to C16-(AYSSGAPPMoxPPF)2-based single-helix
syntheses, resulting in decreased helix length and narrowing of the
helix length distribution. Kinetic studies of fiber assembly were
performed to investigate the mechanism by which the modulator affects
helix length. It was found that the modulator leads to rapid peptide
conjugate nucleation and fiber growth, which in turn results in large
amounts of short fibers that serve as the underlying scaffold for
the single-helix superstructures. These results constitute important
advances toward generating monodisperse samples of plasmonic helical
colloids.