Rational design of a redox-labeled chiral target for an enantioselective aptamer-based electrochemical binding assay

Article abstract of DOI:10.1002/chem.201302979

A series of redox-labeled L-tyrosinamide (L-Tym) derivatives was prepared and the nature of the functional group and the chain length of the spacer were systematically varied in a step-by-step affinity optimization process of the tracer for the L-Tym aptamer. The choice of the labeling position on L-Tym proved to be crucial for the molecular recognition event, which could be monitored by cyclic voltammetry and is based on the different diffusion rates of free and bound targets in solution. From this screening approach an efficient electroactive tracer emerged. Comparable dissociation constants K_d were obtained for the unlabeled and labeled targets in direct or competitive binding assays. The enantiomeric tracer was prepared and its enantioselective recognition by the corresponding anti-D-Tym aptamer was demonstrated. The access to both enantiomeric tracer molecules opens the door for the development of one-pot determination of the enantiomeric excess when using different labels with well-separated redox potentials for each enantiomer. Trace compounds: Redox tracers have been synthesized for enantioselective electrochemical ligand binding assays by relying on the combined use of an oligonucleotide-aptamer receptor with the detection of the redox label. A rational step-by-step optimization procedure has been developed leading to a redox-labeled L-tyrosinamide derivative (see figure) conserving the high affinity towards the aptamer.