And so this band represents those proteins that are the largest in size. And this band represents the proteins that are the smallest in size. Remember, in SDS polyacrylamide gelatrophrases, these proteins move as a result of charge, as a result of being inside an electric field. And the largest proteins move the slowest because they have the greatest resistance. Now, once we form the setup, we also basically want to form the monoclonal antibody that is specific for that protein that we want to study. And that protein that we want to study, we call the antigen.