A specific affinity chromatography method where a molecule of interest (bait) is bound to a column, often via an affinity tag expressed as a protein fusion (GST, HIS tag and others) or chemically linked to the bait molecule . The molecule may be expressed or synthesised and purified first, often in an heterologous system, bound to the matrix at high concentration and then challenged with a solution or cellular extract containing the candidate partner molecules. Alternatively, a multi-molecular complex may be adsorbed to the resin and the retained binding molecules subsequently identified. [ http://www.ncbi.nlm.nih.gov/pubmed/14755292 ]