The Effect of the Antigen’s Molecular Weight on the Curvature of the Precipitin Line in the Ouchterlony Technic

Summary Seven highly purified antigens of known molecular weights ranging from 30,000 to 2,000,000 were studied by the Ouchterlony gel diffusion technique. It was found that the curvature of the precipitin line is related to the molecular weight of the antigen, i.e., a straight line is obtained when the antigen has approximately the same molecular weight as the antibody; if the line curves away from the antibody reservoir, the antigen is heavier than antibody; if it curves towards the antibody reservoir, the antigen is lighter than antibody. The theoretical and practical aspects of these findings are discussed.