Thermodynamic analysis of the interactions of a mouse dinitrophenyl‐specific myeloma protein, MOPC 315, with immobilized dinitrophenyl and trinitrophenyl ligands by affinity electrophoresis

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Abstract
Affinity electrophoresis was applied to determine the dissociation constants and the thermodynamic parameters for the interactions between the mouse myeloma, MOPC 315, and trinitrophenyl (Tnp) and dinitrophenyl (Dnp) haptens. The myeloma protein consists of monomeric, dimeric, and trimeric forms of IgA. The dimer had a higher affinity to the haptens than the monomer, but its Fab' fragment had lower affinity than the monomer. All of these myeloma proteins had higher affinities to Tnp‐hapten than to Dnp‐hapten. The affinity of MOPC 315 proteins increased when the temperature increased. The van't Hoff plots for all of these interactions gave straight lines within the temperature range from 7 °C to 40 °C. The ΔH° were calculated by using the linear van't Hoff plots. The ΔS° were calculated from the D̊H° and D̊G°. The D̊H° and D̊S° were both positive. Hence, the interactions were endothermic and hydrophobic.