Figure 3. SV-AUC profiles showing continuous size distribution against sedimentation coefficient and apparent solution molecular weight. Apparent molecular weights have been determined from the sedimentation coefficients with cartoon images representing the multimeric state of the main population. (A) IgG4 Fc WT has a mass indicative of a dimeric species with only a small fraction of monomer detectable at 2.4 S. (B) IgG4 Y349D has broadened profile consistent with a rapid equilibrium between monomeric and dimeric species and an average sedimentation coefficient of 3.5S (C) IgG4 Fc T394D has a calculated mass representing monomer with no detectable dimer at 3.7 S.