A chimeric intact antibody and single-chain Fv-Fc (scFv-Fc) fragment. (a) Schematic representation of a chimeric intact antibody and single-chain Fv-Fc (scFv-Fc) fragment. The table below the figure indicates the molecular weight and half-life of the antibodies. Also as shown, mutating the Fc region of an antibody at residue 310 from a histidine to an alanine will change the half-life significantly to only 27 h. (b) SDS-PAGE and Western blot of the anti-CEA scFv-Fc (H310A) antibody. The black arrow points to the purified antibody. (c) Size exclusion chromatography of intact CEA antibody, Anti-CEA scFv-Fc H310 antibody, and BSA. The peak of the scFv-Fc between the intact antibody and BSA confirms its intermediate size.