Lyotropic liquid crystals formed from ACHC-rich β-peptides.

We have examined the effect of β-peptide modifications on the propensity of these helical molecules to form lyotropic liquid crystalline (LC) phases in water. All of the β-peptides we have examined contain 10 residues. In each case, at least three residues are derived from trans-2-aminocyclohexanecarboxylic acid (ACHC), which strongly promotes folding to a 14-helical conformation.

Oriented aggregation: formation and transformation of mesocrystal intermediates revealed.

Oriented aggregation is a special case of aggregation in which nanocrystals self-assemble and form new secondary single crystals. This process has been suggested to proceed via an intermediate state known as the mesocrystal, in which the nanocrystals have parallel crystallographic alignment but are spatially separated. We present the first direct observations of mesocrystals with size and shape similar to product oriented aggregates by employing cryo-TEM to directly image the particles in aqueous suspension.

Gold nanoparticles can induce the formation of protein-based aggregates at physiological pH.

Protein-nanoparticle interactions are of central importance in the biomedical applications of nanoparticles, as well as in the growing biosafety concerns of nanomaterials. We observe that gold nanoparticles initiate protein aggregation at physiological pH, resulting in the formation of extended, amorphous protein-nanoparticle assemblies, accompanied by large protein aggregates without embedded nanoparticles. Proteins at the Au nanoparticle surface are observed to be partially unfolded; these nanoparticle-induced misfolded proteins likely catalyze the observed aggregate formation and growth.

Characterization of nanofibers formed by self-assembly of beta-peptide oligomers using small angle x-ray scattering.

Helical oligomers of beta-peptides represent a particularly promising type of building block for directed assembly of organic nanostructures because the helical secondary structure can be designed to be very stable and because control of the beta-amino acid sequence can lead to precise patterning of chemical functional groups over the helix surfaces. In this paper, we report the use of small angle x-ray scattering measurements (SAXS) to characterize nanostructures formed by the directed assembly of beta-peptide A with sequence H(2)N-beta(3)hTyr-beta(3)hLys-beta(3)hPhe-ACHC-beta(3)hPhe-ACHC-beta(3)hPhe-beta(3)hLys-ACHC-ACHC-beta(3)hPhe-beta(3)hLys-CONH(2). Whereas prior cryo-TEM studies have revealed the presence of nanofibers in aqueous solutions of beta-peptide A, SAXS measurements from the nanofibers were not well-fit by a form factor model describing solid nanofibers.

Peptide amphiphile nanofibers template and catalyze silica nanotube formation.

Hollow silica nanotubes with tunable dimensions have been synthesized by condensation of tetraethoxysilane (TEOS) on peptide-amphiphile nanofiber templates followed by calcination. Peptide-amphiphile nanofibers direct silica mineralization by providing nucleation sites and catalyze silica polymerization at their surface. The catalytic activities of peptide-amphiphiles containing lysine, histidine, or glutamic acid were compared and only peptide amphiphiles containing lysine or histidine were found to be good catalytic templates.