Designed Amphiphilic β‑Sheet Peptides as Templates for Paraoxon Adsorption and Detection

Amphiphilic peptides were designed to fold into a β-sheet monolayer structure while presenting the catalytic triad residues of the enzyme, acetylcholinesterase (Glu, His, and Ser), to a solution containing the organophosphate, paraoxon. Three peptides, in which the catalytic triad residues were arranged in different orders along the strand, were generated to reveal potential differences in interactions with paraoxon as a function of the order of these amino acids. One additional peptide with amino acids introduced in random order was studied to highlight the contribution of the β-sheet secondary structure to any interactions with paraoxon. Langmuir isotherms, Brewster angle microscope at interfaces, and circular dichroism measurements in bulk showed that both the β-sheet conformation and the order of the amino acids along the strand influenced the interactions of paraoxon with the peptides. Compression isotherm curves as well as Brewster angle microscopy images provided evidence for enhanced adsorption of the paraoxon to the monolayers of peptides, which present neighboring Glu and Ser residues along the hydrophilic face of the β-strand. Circular dichroism revealed that the peptide most sensitive to interactions with paraoxon was that with the triad residues in the order Glu, Ser, and His, which appears to be appropriate for supporting a catalytic mechanism similar to that in the acetylcholinesterase enzyme. These rationally designed peptides may be further used for the development of technologies for organophosphate adsorption and detection.