QCM analysis for the formation of a self-assembled peptide membrane and high sensitivity detection of porphyrin

In this study, the purpose was to construct a system for the high sensitivity detection of low molecular weight compounds using a peptide ligand and quartz crystal analyzer (QCA). Porphyrin (H/sub 2/TMpyP) was used as the target compound and a self-assembled monolayer (SAM) of porphyrin binding peptide was used as a ligand. The peptide SAM formation on the gold surface was monitored by the measurement of the resonant frequency. The interaction between the peptide SAM and porphyrin was continuously detected using QCA. The clear frequency decrease for the peptide-SAM formation and porphyrin binding appeared readily after the injection of peptide solution and porphyrin solution. Although in the direct measurements the frequency decrease was observed only for high-concentrated porphyrin over 20 /spl mu/g/ml. The detection system could be improved by the addition of peptides immobilized on latex beads used as a mass-sensitizer. The detection limit of this system was 10 ng/ml.