Chemical and Immunological Properties of Reduced and Alkylated Polypeptide Chains of Bovine Fibrinogen

The α, β and γ chains were isolated from reduced and carboxymethylated bovine fibrinogen by chromatography on CM‐cellulose. Electrophoretically pure polypeptide chains could be obtained as judged by three different methods. The chains were soluble in buffers at or above pH 8 but exhibited non‐covalent aggregation. The molecular weights of the α, β and γ chains were estimated in dodecylsulfate‐polyacrylamide gel electrophoresis as 62000, 58000 and 48000, respectively. Each chain differed considerably from the other in amino acid composition as well as in the fragment pattern obtained after CNBr treatment. The occurrence of unresolved α/β material suggested microheterogeneity of the individual chains. Sulfitolysis yielded, at least for the α chain, less pure products. Between 20% and 54% of the antibodies in rabbit antisera to native fibrinogen precipitated with the α and/or β chain. Absorption studies, gel precipitation and hemagglutination‐inhibition suggested a considerable antigenic homology of both chains. They could be clearly distinguished from the γ chain which reacted poorly in precipitation test but considerably better in passive hemagglutination. Cyanogen bromide cleavage did not destroy the serologic activity of the chains. These findings indicated that a considerable number of the antigenic determinants on fibrinogen are not dependent on intact conformation. However, antibodies specifically reacting with the native molecule occur as well.