Site-specific protein immobilization through N-terminal oxime linkages

Immobilizing proteins in specific orientations is important for diagnostic protein arrays, biomaterials, and other applications where retention of bioactivity is essential. We report an approach for protein micropatterning that exploits a chemoselective reaction to conjugate proteins at the N-terminus to polymer films. A copolymer from 2-hydroxyethyl methacrylate and a Boc-protected aminooxy tetra(ethylene glycol) methacrylate was synthesized by radical polymerization. Boc groups were locally deprotected using photoacid generator-based photolithography. Micropatterns were verified by fluorescence microscopy utilizing green fluorescent aldehyde microspheres. Streptavidin that was subjected to a transamination reaction to install an α-ketoamide group at the N-terminus was conjugated to the patterns by oxime bond formation. Since the majority of proteins may be modified to contain a reactive carbonyl group, this methodology should be applicable to pattern a wide variety of proteins specifically through the N-terminus.