Quantitation of Interacting Molecular Species and Measurement of Molecular Avidity by Single Radial (Immuno) Diffusion

Abstract

Abstract : The single radial diffusion (SRD) assay was originally developed by Mancini et al. for the quantitation of antigen or antibody. In the present, this method was applied to the study of any molecular interacting system involving the formation of a precipitate. The binding component of the system may or may not be an antibody, and can be a solubilized aggregate. The use of the number of moles or equivalences instead of the mass units to represent the amount of the interacting components was also introduced to yield information on molar or equivalent basis. The SRD method was used to study endotoxins (or lipid A) and their interactions with a broad spectrum of agents, e.g. new methylene blue, an anti-lipopolysaccharide factor from horseshoe crab, and monoclonal antibodies against lipid A. Molecules such as dextran sulfate, heparin and succinylated bovine serum albumin carrying multiple anionic groups similar to endotoxin aggregates, also demonstrated clear SRD phenomena.