STUDIES ON THE CHARACTERIZATION AND STRUCTURE OF THE IMMOBILIZATION ANTIGENS OF PARAMECIUM AURELIA.

1. Methods for the extraction and purification of the immobilization antigens of Paramecium aurelia have been developed. 2. The immobilization antigen was shown to be a protein of molecular weight 250000. The amino acid content of two allelic antigens and one controlled by a separate genetic locus was determined and many differences were observed. 3. The properties of antigen denatured by reduction and alkylation were examined. The molecular weight fell to 80000 or perhaps less. 4. Peptide maps of allelic types were more similar than those of types controlled by different genetic loci. 5. It is suggested that the antigen consists of two identical half-molecules held together by disulphide bonds. These half-molecules may contain further sub-units.