Zimmerman, B, Shalatin, N. and Howard M. Grey, (1971), Biochemistry 10: 482-488.
Structural studies on the duck 5.7S and 7.8S immunoglobulins revealed the former to have a molecular weight of 118,000, an Fab fragment of 48,000 and component heavy and light chains of 35,000 and 23,000 respectively. The carboxy-terminal residue on the heavy chain was phenylalanine and the molecule had a relatively low total carbohydrate content of 0.6%, which was localized to the Fab fragment. The 7.8S immunoglobulin was shown to have a molecular weight of 178,000 with a heavy chain of 62,000-66,000. The total carbohydrate was 5.0%. Both proteins are structurally distinct from previously described mammalian immunoglobulins. The phylogenetic implications of these findings with respect to immunoglobulin evolution are discussed.