Conformational selective Xaperone (blue) in complex with the active conformation of the β2-adrenergic receptor (green). View of β2AR with the CDRs of the Xaperone in brown (CDR1), purple (CDR2) and red (CDR3) that have amino acids within 4Å of the receptor. The longer CDR3 loop penetrates 13 Å into the receptor.

Xaperones have a single domain structure

Xaperones are antibody-derived single domain proteins that contain the unique structural and functional properties of naturally-occurring heavy chain only antibodies.The Xaperones we isolate are stable polypeptides harbouring the full antigen-binding capacity of the original heavy chain only antibodies.

Xaperones are easy to manufacture

Xaperones are encoded by single genes and are efficiently produced in prokaryotic and eukaryotic hosts including bacteria and yeast. Xaperones exhibit a superior stability compared to conventional antibodies and derivatives thereof like F_ABs or scFvs.

Xaperones recognize cryptic epitopes

As a result of their small size, Xaperones can recognise epitopes that are hidden or shielded from the much larger conventional antibodies.

Xaperones bind cavities on enzymes and receptors

Due to their unique 3-dimensional structure, Xaperones have access to cavities within molecular targets such as active sites of enzymes or clefts on receptors. These cavity structures are largely inaccessible to conventional antibodies but can be readily recognised by a long and protruding peptide CDR3 loop.

Xaperones bind native conformational epitopes 

Xaperones bind discontinuous amino acids that come together in native conformations, i.e. conformational epitopes. Xaperones can selectively stabilize distinct conformers of conformationally rich proteins.