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    Self-Assembly and Rearrangement of a Polyproline II Helix Peptide on Gold

    Year: 2021

    Journal: Langmuir, Volume 37, MAY 25, page 6115–6122

    Authors: Hostert, Jacob D.; Loney, Charles N.; Pramounmat, Nuttanit; Yan, Katherine; Su, Zihang; Renner, Julie N.

    Organizations: United States Department of Agriculture [2018-68011-28691]; National Science Foundation [1739473, 2026259]; U.S. Department of Energy, Office of Science, Basic Energy Sciences, Catalysis Science Program [DE-SC0016529]

    Polyproline peptide sequences have gained popularity as anchors for peptide-based self-assembled monolayers (SAMs) due to their attractive 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 (GPPPPPG)(2)C. 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 kt. 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 Delta G(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 high molecular density SAMs consisting of PPII helices. In addition, 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 in the designing of future peptide-based SAMs with high surface coverage and antifouling properties.
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