(112b) Self-Assembly and Rearrangement of a Polyproline II Helix Peptide on Gold

Polyproline peptide sequences have gained popularity as anchors for peptide-based self-assembled monolayers (SAMs) due to their attractive packing properties. In this work, peptides containing the polyproline II helix (PPII) conformation were designed and assembled on gold (Au). A quartz crystal microbalance with dissipation was used to characterize SAM formation kinetics and related properties. Peptides were designed with the sequence (GPP-P-PPG)₂C. It was discovered that a biexponential adsorption and rearrangement model describes the binding kinetics of the PPII-containing peptide on Au. In this model, an initial reversible binding step is followed by an irreversible rearrangement step, given by parameter k_t. This study found k_t to be approximately 0.00064 s^-1 for the PPII-containing peptides. Similarly, we found that the adsorption of the PPII-containing peptide on Au – given by ΔG_ads – was thermodynamically favorable (-7.8 kcal mol^-1), and comparable to other common thiol terminated SAMs on Au. Furthermore, we characterized SAM properties via QCM-D, Fourier-transform infrared (FTIR) spectroscopy and electrochemical techniques to reveal well-packed SAMs consisting of PPII helices. Last, these SAMs were found to have high antifouling properties. Overall, this study characterizes the fundamental assembly mechanisms, particularly rearrangement, of PPII-containing peptides for the first time, which will be useful when designing future peptide-based SAMs with high packing and antifouling properties.