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The properties of nanoparticle superstructuresdepend on many factors,including the structural metrics of the nanoparticle superstructure(particle diameter, interparticle distances, etc.). Here, we introducea family of gold-binding peptide conjugate molecules that can directnanoparticle assembly, and we describe how these molecules can besystematically modified to adjust the structural metrics of lineardouble-helical nanoparticle superstructures. Twelve new peptide conjugatesare prepared via linking a gold-binding peptide, AYSSGAPPMPPF(PEPAu), to a hydrophobic aliphatic tail. The peptide conjugateshave 1, 2, or 3 PEPAuheadgroups and a C12,C14, C16, or C18aliphatic tail.The soft assembly of these peptide conjugates was studied using transmissionelectron microscopy (TEM), atomic force microscopy (AFM), and infrared(IR) spectroscopy. Several peptide conjugates assemble into 1-D twistedfibers having measurable structural parameters such as fiber width,thickness, and pitch that can be systematically varied by adjustingthe aliphatic tail length and number of peptide headgroups. The linearsoft assemblies serve as structural scaffolds for arranging gold nanoparticlesinto double-helical superstructures, which are examined via TEM. Thepitch and interparticle distances of the gold nanoparticle doublehelices correspond to the underlying metrics of the peptide conjugatesoft assemblies, illustrating that designed peptide conjugate moleculescan be used to not only direct the assembly of gold nanoparticlesbut also control the metrics of the assembled structure. [ABSTRACT FROM AUTHOR]