The present invention relates to a polypeptide monobody which includes a
modified acid sequence and renders the polypeptide monobody able to bind
selectively to .alpha..nu..beta.3 integrin. Fusion proteins and
conjugates which include the polypeptide monobody, as well as
compositions containing the polypeptide monobody, fusion proteins, or
conjugates are also disclosed. Uses thereof include: treating or
preventing an .alpha..nu..beta.3 integrin-mediated disease or disorder,
inhibiting .alpha..nu..beta.3 integrin activity, treating a cancerous or
precancerous condition, imaging tissues using positron emission
tomography or magnetic resonance imaging, assessing the metastatic
characteristics of a tumor, and delivering DNA to a cell.