Analysis of Opioid and Amyloid Peptides Using Time-of-Flight Secondary Ion Mass Spectrometry

The imaging capability and high detection sensitivity of time-of-flight secondary ion mass spectrometry (ToF-SIMS) makes it a potentially attractive complement to other mass spectrometry methods, such as ESI and MALDI, for the analysis of proteins and peptides. We have explored this possibility by performing a systematic analysis of synthetic opioid and amyloid peptides with ToF-SIMS using Bi-3(+) and Au-3(+) primary ions. In the low mass region of the spectra, a number of single amino acid ion peaks were detected, providing information about the amino acid content in each peptide. In the medium and high mass range of the spectra, peaks corresponding to multiple amino acid ions (backbone cleavage ions) as well as molecular ions were detected, allowing for the determination of the amino acid sequence and the molecular mass of the entire peptide, respectively. Detection efficiencies were determined for the molecular ions of some of the peptides, indicating detection limits in the attomole range. The fragmentation patterns observed in the ToF-SIMS analysis of opioid and amyloid peptides showed interesting similarities with collision-induced dissociation (CID) studies using other mass spectrometry methods. The present work provides important progress toward ToF-SIMS proteomics.