Affilin

Affilin® artificial proteins have the ability to selectively bind antigens. Affilin® is a registered trademark of Scil Proteins GmbH. Affilin proteins are structurally derived from human ubiquitin (historically also from gamma-B crystallin). Affilin proteins are constructed by modification of surface-exposed amino acids of these proteins and isolated by display techniques such as phage display and screening. They resemble antibodies in their affinity and specificity to antigens but not in structure, which makes them a type of antibody mimetic. Affilin proteins are being developed as potential new biopharmaceutical drugs, diagnostics and affinity ligands.

Structure

Two proteins, gamma-B crystallin and ubiquitin, have been described as scaffolds for Affilin proteins. Certain amino acids in these proteins can be substituted by others without losing structural integrity, a process creating regions capable of binding different antigens, depending on which amino acids are exchanged. In both types, the binding region is typically located in a beta sheet structure, whereas the binding regions of antibodies, called complementarity determining regions, are flexible loops.