Determination of the number of Fab1 pieces which react with high molecular weight antigens

The sedimenting-droplet technique was used for the determination of the masses of immune Fab1 pieces which may bind to antigenic sites on three haemocyanins. Similar experiments were conducted on three viruses which belong to the Tobamo group. It was calculated that 384 homologous Fab1 pieces could bind to a molecule of the haemocyanin of Burnupena cincta and 950 homologous Fab1 pieces to a virion of tobacco mosaic virus. By taking special precautions the number of undegraded antibody molecules which can bind to a Tobacco mosaic virus particle may be determined with the same technique.