Online monitoring of solid-phase peptide syntheses on glass-type surfaces using white light interference

Label-free optical detection methods are of particular value for the investigation of biomolecular interactions. A label-free method based on reflectometric interference spectroscopy is described which enables both the on-line monitoring of solid phase peptide syntheses and subsequently the determination of antibody binding to these peptides without cleavage from the support. The method uses SiO(2) transducers that were modified with diaminopolyethylene glycol. The stepwise coupling of different amino acids to the transducer surface was investigated and the complete monitoring of the synthesis of a viral epitope was performed. The success of the synthesis was proven via binding of a specific monoclonal antibody to the transducer-bound product. In order to demonstrate specificity the binding was inhibited with the same peptide epitope added in solution. The approach is attractive especially in the field of high throughput screening since both the synthesis and the interaction with the biological receptor can be monitored using the same technique.