A mixture of proteins is analyzed by Western blotting. Two proteins with molecular weights of 45,000 Da and 75,000 Da are stained after using monoclonal antibody A. When the same experiment is performed with a different monoclonal antibody (B), the same 45,000 Da protein appears as does another protein with a molecular weight of 67,000 Da. Propose an explanation for these results. (Hint: think structurally)