Protein L Affinity Resin

Protein L is an immunoglobulin-binding protein, originally derived from the bacterium Peptostreptococcus magnus (now Finegoldia magna), that is widely used as an affinity ligand for purifying antibodies. Unlike Protein A and Protein G, which bind the Fc region of IgG, Protein L binds to the variable region of kappa (κ) light chains. Because the light chain is shared across antibody classes, this allows Protein L to capture not only IgG but also IgM, IgA, IgE, IgD, as well as Fab and single-chain variable fragments (scFv)—provided they carry a κ light chain of a reactive subtype. This Fc-independent binding makes Protein L especially useful for purifying antibody fragments and antibodies from species or formats that lack a suitable Fc region for Protein A or G. BiCell Scientific’s protein L affinity resin uses 4% highly cross-linked agarose matrix with a mean size of 90 μm and capable of operating under 0.1 MPa (1 bar/14.5 psi). The hydrophilic nature of the matrix ensures low levels of non-specific binding leading to low levels of host cell-derived impurities in the elution pool. The recombinant protein L ligand is expressed in E. coli and free of any components of mammalian origin.