We initially altered two loops of FNfn10 that are structurally equivalent to two of the hypervariable loops of the immunoglobulin domain. We have developed small antibody mimics, 'monobodies', using FNfn10 as a scaffold. The tenth fibronectin type III domain of human fibronectin (FNfn10) is a small, monomeric beta-sandwich protein, similar to the immunoglobulins.