Antibody studies into the human immunodeficiency virus (HIV) centre around Gag, a highly complex polyprotein that has so far defied attempts to unravel its complex and varied modes of action. Now, a team from the NIST Center for Neutron Research have revealed a new model which has allowed the protein to be studied in far more clarity. The hope with antibody suppliers is that it will pave the way to understanding many more large, unfathomable proteins.