Synthesis of well-defined methacrylate copolymers and their use for stabilizing membrane proteins

We describe the synthesis of a novel series of amphiphilic methacrylate copolymers composed of one hydrophobic monomer carrying a cyclohexyl group and one hydrophilic monomer carrying a short poly(ethylene glycol) chain comprising 6, 9, or 19 units. RAFT polymerization was used to yield well-defined polymers. First, we studied the kinetic of this copolymerization and calculated the reactivity ratios according to different linear least-squares (LLS) methods. We thus could demonstrate the statistical copolymerization of the two monomers. Then, by varying the ratio of each monomer in the copolymerization, we developed a series of polymers that were tested for their abilities to extract membrane proteins from Escherichia coli cells overexpressing the Bacillus subtilis multidrug resistance ABC transporter (BmrA) and to stabilize the light-driven proton transporter bacteriorhodopsin (bR). While our copolymers failed to directly extract significant amounts of proteins, they were found to provide stabilizing environments for extracted membrane proteins, suggesting they could be used as non-ionic stabilizing polymers. image