Abstract
Following our recent study of the binding of antigen hCG (human chorionic gonadotropin) onto a mouse monoclonal antibody anti-β-hCG immobilized onto the support surface, we report a more recent study of the site-specific recognition of another surface immobilized mouse monoclonal antibody anti-α-hCG by hCG. The two antibodies have similar structures and molecular weights but different site-specific recognition from hCG. They both are used in the fabrication of fertility test immunoassays. Previous study by neutron reflection has indicated the “flat-on” orientation of anti- β-hCG with its Fc and two Fabs lying flat on the support surface. The aim of this work is to determine if there is any measurable difference in hCG binding between the two antibodies that could be attributed to the steric hindrance associated with specific binding sites. The adsorption and hCG binding for anti-α-hCG were made under the surface and in solutions as for anti-β-hCG so that the outcome could be directly compared. The results show that the two antibodies are bound by hCG in an almost identical fashion, suggesting that apart from the site-specific recognition there is no measurable difference in the steric hindrance between the α and β sites.