Revealing Single-Amino Acid Recognition and Cleavage Dynamics Using Plasmonic Biosensors

High-resolution proteome analysis depends on accurately determining the primary structure of proteins to advance our understanding of biological systems. Conventional peptide sequencing techniques, such as Edman degradation and mass spectrometry, often require substantial sample input, limiting their sensitivity for low-abundance proteins. Although the fluorescent method offers an alternative for single-molecule protein sequencing, the lack of a comprehensive fluorophore repertoire for labeling recognizers for all 20 amino acids impedes further development. Here, we present a versatile optical biosensing platform based on surface plasmon resonance (SPR) technology. The integration of 2D GeP₅ nanosheets significantly enhances the plasmonic response, improves the sensitivity of the SPR biosensor, and scrutinizes biomolecular interactions in real time. Neoteric SPR has the unique ability to recognize and cleave the ordered appearance of N-terminal amino acids in peptides. With an excellent performance of single-residue resolution, the successive dynamics of the "recognition-cleavage-re-recognition" process are attained using the label-free biosensing method.