Quantitative Antigen Analysis by the Oudin Method

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Abstract
Summary: The results of an attempt to utilize the agar diffusion technique of Oudin as a means of quantitatively evaluating the amount of antigen in a solution were presented. The linear relation between the logarithms of the antigen and antibody concentrations, and k, as reported by others, (3, 4) was confirmed, and empirical equations for egg albumin and bovine serum albumin systems were presented. The results of Becker et al. (4) were confirmed in that it was found possible to calculate the diffusion coefficient of these antigens by a derivative of Fick's equation for diffusion, though only to a rough approximation. Further, the results obtained agreed excellently with those obtained for the same antigens by these authors. The value of the diffusion coefficient so calculated depended on the ratio of antigen to antibody, and the best results for the diffusion coefficient were found at the highest ratios. The effect of increasing saline and protein (non-cross-reacting) content on the migration of the specific precipitate ring was studied. It was found that increasing the saline or protein content of the medium in which the antigen was suspended increased the velocity of descent of the ring, and that the increase in velocity thus demonstrated reached a maximum at 2–2.5% saline, or protein, or total saline and protein, concentration.