Interactions of Polyproline II Helix Peptides with Iron(III) Oxide

Interactions of a peptide with polyproline II helical secondary structure with maghemite (iron(III) oxide, Fe₂O₃) surfaces were characterized using a variety of surface techniques. A quartz crystal microbalance with dissipation was used to measure the hydrated mass and thickness (92 ± 29 ng/cm² and 0.89 ± 0.27 nm, respectively) of a layer which formed after a sensor coated with Fe₂O₃ was exposed to the peptide in aqueous solution. The analysis revealed that the peptide formed a stable thin layer on the sensor. X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy of the monolayer were employed to study the relationship between the metal and the peptide. Finally, Fe₂O₃ nanoparticles were incubated with the peptide, and analysis of the settling and particle size revealed that the presence of the peptide reduced the occurrence of large aggregates in solution.