On the weight of precipitate obtainable in precipitin interactions

Abstract

The nature of the interaction between the antiserum and homologous protein in a precipitin test has been the subject of several researches. It has been usual to mix a given fixed quantity of suitably diluted homologous protein estimated either directly or in terms of dilutions and to measure the volume of the precipitate formed. The experiments of Hamburger which have been analysed by Arrhenius were conducted in this way. Welsh and Chapman also examined mixtures of a fixed quantity of antiserum with increasing quantities of homologous protein by adding to the superfluid above the precipitate either antiserum or homologous protein. This mode of testing the superfluid always led to the formation of a further precipitate. In the second place it was possible to neutralise completely the precipitin in an antiserum, so that the further addition of homologous protein led to no more formation of precipitate. The precipitin reaction between antigen and anti-body is very suitable for quantitative study owing to the simple nature of the interaction and the ease with which the quantities may be measured. More accurate methods are, however, required for its study than those previously employed. The present paper records the results of a gravimetric study of the reaction. The weights of the two interacting bodies and the weight of the final precipitate have been ascertained. The precipitin (anti-body present in the serum of the immunised animal) cannot be directly determined by weighing, as it forms only a small part of the dried antiserum. The homologous protein (either serum or egg-white) has been reckoned as milligrammes of dried serum or dried egg-white. The precipitate formed in the interaction has been weighed.