Strategies for generation of designer zinc-finger proteins. A. Greisman et al.  described the process of growing an artificial zinc-finger through the sequential panning of a phage library for each of the three fingers. B. OPEN zinc finger design selects zinc-fingers by screening an archive of characterized zinc fingers for each DNA triplet, followed by random PCR assembly and selection of the best assembled zinc finger trimer. C. The bipartite design relies on two libraries in which either the first half (library 1) or the second half (library 2) of the Zif268 zinc finger DNA binding residues has been randomized.