L-Pro functionalized carbon nanoclusters inducing an enantioselective voltammetric response to Trp and Tyr

Chiral carbon nanoclusters from D-glucose (D-Glu), covalently decorated on the surface with L-proline (L-Pro) have been electrografted on a glassy carbon electrode (GCE), obtaining a chiral glassy carbon electrode (L-Pro@Glu-GCE). The Differential Pulse Voltammetric behaviour of L-Pro@Glu-GCE depends on the absolute configuration of the analyte i.e. tyrosine (Tyr) or tryptophan (Trp). A difference of 35.3% in oxidation peak current is obtained with L- or D-Tyr (L-Tyr giving a higher peak current), while a smaller one, 9.4%, is obtained with L- or D-Trp, with an inverse selectivity (D-Trp giving a higher peak current). The fluorescence analyses on solutions of L-Pro@Glu in the presence of L- and D- Tyr and Trp confirmed such enantioselective interaction. Theoretical calculations were able to demonstrate that the aggregate between L-Pro@Glu and L-Tyr is more stable than the aggregate with D-Tyr of 76 meV, confirming the results obtained with DPV and fluorescence analyses.