Protein G GraviTrap are prepacked gravity-flow columns designed for fast and efficient manual purification of monoclonal and polyclonal antibodies, antibody fragments from cell culture supernatant, and biological fluids. The antibodies are simply captured with high specificity on protein G ligands in gravity-flow columns. You do not need any other instrument with this protocol because the entire process relies on the flow of gravity. The yield varies from 20 to 50 mg of purified antibodies depending on the ligand you use. The columns are reusable up to five times.