Differential self assembly of amphiphilic helical peptides.

A series of amphiphilic, helical peptides was designed and synthesized to investigate the components necessary for formation of helical bundles with differing aggregation states. Minimalistic sequences were employed for the peptides which contained either four (Leu4), six (Leu6) or eight (Leu8) leucine residues within a sixteen amino acid sequence. All peptides were highly helical as evaluated by circular dichroism, and the helical content of each peptide exhibited a concentration dependence. Size exclusion chromatography confirmed aggregation states of dimer/trimer forLeu4, tetramer forLeu6, and hexamer octamer forLeu8. Disulfide crosslinking studies also confirmed that the dimer ofLeu4 favored a parallel orientation with respect to the helical dipole. This systematic study clearly defines the role of hydrophobicity in the self assembly of helical peptides; peptides with a small hydrophobic face favor small bundle sizes, whereas peptides containing larger hydrophobic faces form correspondingly larger helical bundles.