Synthesis of Well-Defined (Nitrilotriacetic Acid)-End-Functionalized Polystyrenes and Their Bioconjugation with Histidine-Tagged Green Fluorescent Proteins

We have synthesized nitrilotriacetic acid end-functionalized polystyrene (NTA–PS) for the controlled bioconjugation with histidine-tagged green fluorescence proteins (His6–GFP). NTA–PS was prepared using initiators containing tert-butyl protected NTA moiety via atom transfer radical polymerization (ATRP) of styrene; the protected tert-butyl group was subsequently removed at the α-chain end of polystyrene. The structure of NTA–PS was characterized using 1H NMR, 13C NMR, and GPC. NTA chain ends of the polystyrenes were complexed with Ni2+ to produce Ni–NTA–PS, of which the specific binding properties were studied by forming spherical aggregates with His6–GFP in aqueous phase. The reversible association of His6–GFP with polystyrene spherical aggregates (with Ni2+) was controlled with imidazole and monitored with fluorescence microscope. Again, Ni–NTA–PS produced well-defined micelles with His6–GFP in water/DMF (DMF 4 vol %) and the size of micelles decreased when excess imidazole was added.