Affinity Capturing and Surface Enrichment of a Membrane Protein Embedded in a Continuous Supported Lipid Bilayer

Investigations of ligand‐binding kinetics to membrane proteins are hampered by their poor stability and low expression levels, which often translates into sensitivity‐related limitations impaired by low signal‐to‐noise ratios. Inspired by affinity capturing of water‐soluble proteins, which utilizes water as the mobile phase, we demonstrate affinity capturing and local enrichment of membrane proteins by using a fluid lipid bilayer as the mobile phase. Specific membrane‐protein capturing and enrichment in a microfluidic channel was accomplished by immobilizing a synthesized trivalent nitrilotriacetic acid (tris‐NTA)–biotin conjugate. A polymer‐supported lipid bilayer containing His(6)‐tagged β‐secretase (BACE) was subsequently laterally moved over the capture region by using a hydrodynamic flow. Specific enrichment of His(6)–BACE in the Ni(2+)–NTA‐modified region of the substrate resulted in a stationary three‐fold increase in surface coverage, and an accompanied increase in ligand‐binding response.