Bisphosphonate molecules preferentially bind to calcium ions. Receptors are proteins that bind small ligands. Antibodies can then bind to these viral proteins. Dynactin can function as a scaffold for other proteins to bind to. Lastly, tPA can bind plasminogen, cleaving off the bound plasmin from it. These receptors bind to the proteinTRAIL and mediate apoptosis. Lisinopril does not bind to proteins in the blood. Porphyrins are the conjugate acids of ligands that bind metals to form complexes. It can weakly bind to some proteins and impart a blue colour. Proteins can also bind to, or even be integrated into, cell membranes. Apparently immunoglobulin (Ig)-binding proteins bind C4BP. Antibody mimetics are organic compounds, like antibodies, that can specifically bind antigens. Unlike arketamine, esketamine does not bind significantly to sigma receptors. Benzodiazepines all bind unselectively to the GABA receptor. Transferrin glycoproteins bind iron tightly, but reversibly.