Effect of Peptide Sequence on Surface Properties and Self-Assembly of an Amphiphilic pH-Responsive Peptide

Peptides that undergo a morphological change when exposed to a stimulus have been investigated for their surface and self-assembly properties. Two 15-residue sequences were designed and synthesized for the purpose of determining the role of sequence on surface properties and peptide self-assembly. The KhK (KKKFLIV-IGSIIKKK) and Alternating Kh (KFLKKIVKIGKKSII) sequences were synthesized via microwave peptide synthesis according to the automated base-labile Fmoc strategy. Despite having the same amino acid content, KhK solutions exhibited an increase in contact angle with increasing pH, whereas Alternating Kh solutions demonstrated a decrease in contact angle with increasing pH. Further analysis by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) showed marked differences in the peptide solution and peptide particle morphology. Circular dichroism (CD) spectroscopy indicated that KhK consisted of primarily beta-sheet conformations at acidic and neutral pH. In Alternating Kh CD spectra, random coil conformations were predominant at acidic and neutral pH.