Effect of posttranslational modifications on the thermal stability of a recombinant monoclonal antibody.

The effect of oligosaccharides and C-terminal lysine residues on the thermal stability of a recombinant IgG(1) monoclonal antibody was investigated using differential scanning calorimetry (DSC). The C-terminal lysine did not appear to affect the thermal stability of this IgG(1) molecule. However, oligosaccharides, which are buried between the two CH(2) domains, provided significant stabilizing energy. Characterization of the Fab and Fc after papain digestion suggested that the stabilizing effect of oligosaccharides on this molecule was through stabilizing CH(2) domains. Oligosaccharides had little effect on the thermal stability of Fab region and CH(3) domains. It was also interesting to note that both intact IgG(1) antibody and its Fab, but not the Fc regions, appeared to form precipitate after thermal unfolding under the experimental conditions.