Isolation of nucleic acid binding molecules. Biotinylated DNA is added to the cell lysate or a protein mixture that contains protein which interacts with the DNA (i). Streptavidin magnetic beads are added that binds to the complex (biotin-DNA-protein) based on its affinity for biotin (ii). The complex is separated magnetically from the mixture (iii). Reprinted, with permission, from materials provided by Miltenyi Biotec, GmbH, Germany.