Enantiomeric recognition of phenylalanine by self-assembled monolayers of cysteine: Surface enhanced Raman scattering evidence

The stereoselective interaction between enantiomers of two amino acids, cysteine and phenylalanine, on roughened silver surface was investigated by SERS spectroscopy. It was demonstrated that the surface coated with one cysteine enantiomer can recognize the phenylalanine enantiomer present in the solution. The change of conformation of some part of adsorbed cysteine molecules from PH to PN caused by the phenylalanine molecules of proper chirality was observed. This effect was attributed to difference in possibility of hydrogen bonding between the NH3+ groups of the surface-attached cysteine molecule with the COO− groups of phenylalanine molecules. Our experiments demonstrate that the SERS spectra are sensitive to chirality of interacting cysteine and phenylalanine molecules at the silver electrode surface, thus indicating the possibility of using this method for enantiomeric recognition of amino acids.