Fluorescent biomolecule, which binds to the ligand. The concentration of target is kept constant throughout Serial Dilution, while the concentration of non-fluorescent Ligand is varied. TRIC is not restricted to a specific type of target molecule. It can be applied to proteins such as Antibodies, Enzymes, GPCRs, Membrane Proteins etc. but also to research on Nucleic Acids and other biologically relevant molecules.

For recommendations about target concentration in TRIC assays see this article: Concentrations.