Ion-specificity in protein binding and recovery for the responsive hydrophobic poly(vinylcaprolactam) ligand

The conformational switch between the hydrophobic state and hydrophilic state of thermo-responsive poly(vinylcaprolactam) (PVCL) has great potential for protein binding and elution applications during protein purification as a hydrophobic interaction chromatography ligand. The lower critical solution temperature (LCST) of PVCL is strongly salt type and salt concentration dependent. Here PVCL polymer chains were grafted on regenerated cellulose membranes using controllable atom-transfer radical polymerization (ATRP) for protein binding/elution studies. Protein binding and recovery demonstrates strong salt type and salt concentration dependency. The effects of salt ions on the static and dynamic binding interactions were elucidated and correlated well with the conformational and hydrophobicity changes of the responsive ligand. The conformational switch between the hydrophobic state and hydrophilic state of thermo-responsive poly(vinylcaprolactam) (PVCL) has great potential for protein purification as a hydrophobic interaction chromatography ligand.