Coupling of MALDI-TOF mass analysis to the separation of biotinylated peptides by magnetic streptavidin beads

Extraction of biotinylated peptides by streptavidin magnetic beads has been directly coupled to the MALDI-TOF mass analysis. The elution of peptides from the beads is achieved by first mixing the beads with the MALDI matrix solution and removing, after a few minutes, the beads with a magnet; then, the matrix solution containing the biotinylated peptide is directly mass analyzed by MALDI. Three examples are presented to show the capabilities of this procedure to detect biotinylated peptides present at very low concentrations in complex mixtures. Detection limits of less than 100 fmol can be achieved. Such a coupling strategy is of great interest to investigate peptide/protein interactions.