Peptide blotting technique using cross-linking magnetic beads. a) Standard peptide mixture spiked with either negative control peptide, positive control peptide, or neither, are spotted onto a slide and cross linked to magnetic beads. The slide is positioned under C18 tape coated with DTT and a transfer magnet. b) The slides are blotted together and the magnetic bead cross-linked peptides are magnetically extracted onto the C18 surface due to the transfer magnet. c) DTT coating on the C18 tape reduces disulfide bonds, releasing cross-linked peptides from magnetic beads. d) The transfer magnet is repositioned below the original slide. e) Free magnetic beads are pulled back onto the original slide due to their attraction to the transfer magnet, leaving freed peptides on the C18 surface for MALDI-TOF IMS analysis.