Electroimmobilization of proinsulin C-peptide to a quartz crystal microbalance sensor chip for protein affinity purification

Proinsulin C-peptide was electroimmobilized to a quartz crystal microbalance sensor chip, localizing this low-pI peptide for covalent attachment to activated surface carboxyl groups. The resulting chip was used in a continuous flow biosensor to capture anti-C-peptide antibodies, which could subsequently be eluted in 5% formic acid between air bubbles for efficient recovery and mass spectrometric identification. The method is reproducible through repeated cycles, providing affinity purification of proteins under real-time monitoring of the binding and elution processes.