Time-of-flight SIMS investigation of peptides containing cell penetrating sequences.

This article focuses on the use of time-of-flight secondary ion mass spectrometry (ToF-SIMS) combined with multivariate analysis to distinguish between four peptides derived from the transactivator of transcription (TAT) protein, including a reference peptide (TAT1) and three variants modified by insertion of a carnosine dipeptide at different positions. Due to extensive fragmentation during ToF-SIMS analysis, direct identification of molecular ions is challenging, so partial least squares discriminant analysis (PLS-DA) was applied to the complex spectral data to achieve effective classification. The study demonstrates that despite the peptides’ similar sequences and compositions, ToF-SIMS coupled with PLS-DA can successfully discriminate between them based on subtle differences in fragmentation patterns. This approach supports the potential of ToF-SIMS and multivariate methods for characterizing biologically functionalized surfaces and peptide modifications relevant to biomedical applications.