Electrochemical enantioselective recognition of tryptophane enantiomers based on chiral ligand exchange

Electrochemical enantioselective recognition of tryptophane (Trp) enantiomers in the presence of Cu(II) using l-cysteine (l-Cys) self-assembled gold electrode is described. The chiral recognition of Trp enantiomers was investigated via cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and quartz crystal microbalance (QCM). Time dependencies of the enantioselective interaction for the l-Cys modified electrodes with Trp enantiomers solutions in the presence of Cu(II) were also studied. The results showed that l-Cys had stronger interaction with d-Trp than l-Trp in the presence of Cu(II), and the discrimination was caused by the selective formation of Cu complexes with l-Cys and Trp enantiomers relying on the principle of chiral ligand exchange. The structure of the Cu complexes was optimized by the hybrid density functional theory (DFT) method. And the enantiomeric composition of l- and d-Trp was monitored by measuring the current responses of the sample.