Abstract 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.