The suitability of mammalian cells as hosts for the production of human proteins is often counterbalanced by relatively low protein yields,attendant difficulties in purifying the target from complex media,and bottlenecks in clone screening and expansion.We have developed a novel mammalian cell-based expression system that circumvents these limitations for the production of high-quality ligands for surface plasmon resonance (SPR) studies.Following simple transient transfection,target ligands are purified on-chip from complex serum-containing media,remain stably bound throughout analyte binding and dissociation phases,and are quantitatively removed from the regeneratable chip surface upon completion of the binding experiment.This method requires only a few microliters of culture medium per interaction and enables the sequential analysis of multiple ligand-analyte pairs on a single sensor chip.Ligand immobilization is stable over a broad temperature range,allowing the comprehensive evaluation of key thermodynamic parameters governing ligand-analyte binding,including △ G°,△H°,T△ S °,and△ Cp.