Electrochemical Evidences of Chiral Molecule Recognition Using L/D-Cysteine Modified Gold Electrodes

Ultrasensitive determination of the chiral nature of a molecule is important for fully understanding protein and DNA structures, and for the design, synthesis and purification of drug molecules. Consequently, development of ultrasensitive detection of chiral molecules is a grand challenge and at the heart of many of today's research fields, including chemistry, biology, biotechnology and pharmacology. Here a novel method afforded by electrochemically tracing the Cu2+ ions that are replaced by L/D-carnitine on anL/D-cysteine modified gold electrode is described. The electrochemical signal of copper ionswas monitored, these were immobilized on the L/D-cysteine functionalized gold electrode surface via cooperative metal-ligand interaction, followed by replacing the Cu2+ with L-carnitine or D-carnitine chiral molecules based on the hetero- or homo- chiral interaction between carnitine and cysteine molecules. The results illustrated that the Cu2+ replacement ratio between L/D-carnitine and D/L-cysteine were higher than that between L/D-carnitine and L/D-cysteine, which is consistent with previous studies that hetero-chiral interaction is stronger than homo-chiral interaction. This study demonstrates a facile, but innovative electrochemical method to probe the chiral recognition of carnitine molecules.