positive reference substance role competitive binding reference ligand role A positive reference substance role that inheres in a material entity that is known to bind to a target entity, and that is realized in a competitive binding assay that has as specified input the target entity, an evaluant and the positive reference substance, where the binding of the evaluant to the target is measured based on the evaluant's ability to compete with the positive reference substance for binding to the target. The role of a radiolabeled peptide that is known to bind to the MHC molecule HLA-A*02:01 with high affinity when it is used in a competitive binding assay in which another peptide of interest is tested for its ability to outcompete binding of the labeled peptide in a dose dependent fashion. Bjoern Peters Bjoern Peters, Randi Vita, James A. Overton competitive binding reference ligand role metadata complete