Designed ankyrin repeat proteins (DARPins) are artificial peptides that bind a specific protein of interest. DARPins are composed of repeating modules that are based on the ankyrin fold; this sequence consists of a β-turn followed by two antiparallel α-helices and binding specificity is determined by particular residues in the α-helices (reviewed in PMID:25562645, PMID:29374062).