As used herein a polypeptide includes protein molecules such as an antibody (e.g., a polyclonal or monoclonal antibody; a bispecific antibody or heteroantibody) and/or functional equivalents thereof such as Fv, Fab, F(ab')2 or variable heavy and/or light chains having an antigen binding site which are produced by proteolytic digests or through recombinant means.