“…Most of these scaffolds employ rather compact, naturally occurring, stable and structurally well-characterized protein modules, comprising secondary structural elements such as helices, β-sheets and loops to varying degrees. They include lipocalins 3 , ankryrin repeat proteins 4 , staphylococcal protein A 5 , fibronectin 6 , -crystallin 7 , ubiquitin 8,9 and others 10 . Typically, these modules are chosen as structural platforms or building blocks for the directed evolution of de-novo binding properties, the latter being achieved by specific amino acid exchanges at selected positions.…”