Figure 3.

Combinatorial peptidomics. Sample solubilisation and protein purification are not necessary, since proteolyric digection may be carried on native cells/tissues (dashed lines). The amino acid filtering (depletion) step may be repeated using combinations of up to 6 amino acid "filters", i.e. chemically reactive surfaces (e.g. derivatised beads) able to covalently cross-link particular amino-acids. Chemical depletion reduces the complexity of the peptide pool to a sufficient degree to make it compatible with direct MS detection.