Water-soluble drug targets such as enzymes are readily produced in drug discovery for screening and X-ray crystallography.In contrast,membrane bound targets such as ion channels and GPCRs are typically screened in cell-based assay or as membrane preparations.Purified membrane proteins would be a valuable asset for drug discovery and would be highly enabling for applications such as antibody generation,affinity-based screening and crystallography.Examples on the purification of human GPCRs and ion channels in functional active form will be given and various applications of such materials will be discussed.