enzymatic footprinting protease accessibility laddering protease access MI:0814 pal In protease accessibility laddering (PAL) tagged proteins are purified on magnetic beads in their natively folded state. While attached to the beads, proteins are probed with proteases. Proteolytic fragments are eluted and detected by immunoblotting with antibodies against the tag (e.g., Protein A, GFP, and 6xHis). PSI-MI