Recombination of heavy and light chains of immunoglobulins. Use of specific variable and constant region probes to monitor reassociation reactions.

The reassociation of antibody (IgG)-derived heavy (gamma) and light (L) chains was studied by utilizing two specifically localized fluorescent probes. L chains labeled in either the variable domain with fluorescein (specific antigen) or the constant domain with N-(iodoacetamidoethyl)-5-naphthylamine-1-sulfonic acid were prepared. Reassociation of these chains with isolated, unlabeled, gamma chains was monitored by following an increase in the fluorescence polarization of fluorophores at 4 degrees C. Results obtained indicate that the reassociation reaction could be resolved into two distinct steps; the primary interaction of the reactants occurring rapidly, followed by a slower secondary phase possibly representing conformational changes in the variable domains of the reactants after reassociation.