Figure 2. The concept of TOF-probes for the selective detection of enzymes with mass cytometry.
Panel A The general architecture of a TOF-probe. A protease-selective peptide is tagged with a stable lanthanide isotope making it suitable for mass cytometry. Panel B A set of protease-selective probes labeled with different metal tags for the parallel visualization of several enzymes. Panel C An outline of the chemical procedure for the high yield synthesis of TOF-probes. Panel D Examples of protease-selective TOF-probes labeled with different lanthanides. In this work we synthesized a panel of eight TOF-probes for four proteases displaying two distinct catalytic mechanisms (legumain, cathepsin L, cathepsin B and human neutrophil elastase) based on previously developed selective peptide sequences.