Abstract: The present invention provides a molecular approach for rapidly and selectively identifying small organic molecule ligands, i.e. compounds, that are capable of interacting with and binding to specific sites on biological target molecules. The methods of the present invention are applicable to any biological target molecule that has or can be manipulated to have a metal-ion binding site. Biological target molecules are e.g. proteins, polypeptides, oligopeptides, nucleic acids, carbohydrates, nucleoproteins, glycoproteins, glycolipids, lipoproteins and derivatives thereof. More specifically, the biological target molecules include membrane receptors, signal transduction proteins, scaffolding proteins, nuclear receptors, steroid receptors, intracellular receptors, transcription factors, enzymes, allosteric enzyme regulatory proteins, growth factors, hormones, neuropeptides and immonoglobulins. A very interesting group of biological target molecules are membrane proteins such as, e.g., transmembrane protein (e.g.