An artificial protein L for the purification of immunoglobulins and Fab fragments by affinity chromatography

The development and characterization of an artificial protein L (PpL) for the affinity purification of antibodies is described. Ligand 8/7, which emerged as the lead from a de novo designed combinatorial library of ligands, inhibits the interaction of PpL with IgG and Fab by competitive ELISA and shows negligible binding to Fc. The ligand 8/7 adsorbent (Ka ∼ 104 M−1) compared well with PpL in binding to immunoglobulins from different classes and sources and, in addition, bound to IgG1 with κ and λ isotypes (92% and 100% of loaded protein) and polyclonal IgG from sheep, cow, goat and chicken. These properties were also reflected in the efficient isolation of immunoglobulins from crude samples.