Effect of polymer chemistry on globular protein–polymer block copolymer self-assembly

The MIT Faculty has made this article openly available. Please share how this access benefits you. Your story matters. Bioconjugates of the model red fluorescent protein mCherry and synthetic polymer blocks with different hydrogen bonding functionalities show that the chemistry of the polymer block has a large effect on both ordering transitions and the type of nanostructures formed during bioconjugate self-assembly. The phase behaviours of mCherry-b-poly(hydroxypropyl acrylate) (PHPA) and mCherry-b-poly(oligoethylene glycol acrylate) (POEGA) in concentrated aqueous solution show that changes in polymer chemistry result in increase in the order–disorder transition concentrations (C ODT s) by approximately 10–15 wt% compared to a previously studied globular protein–polymer block copolymer, mCherry-b-poly(N-isopropylacrylamide) (PNIPAM). The C ODT s are always minimized for symmetric bioconjugates, consistent with the importance of protein–polymer interactions in self-assembly. Both mCherry-b-PHPA and mCherry-b-POEGA also form phases that have not previously been observed in other globular protein– polymer conjugates: mCherry-b-PHPA forms a cubic phase that can be indexed to Ia 3d and mCherry-b-POEGA displays coexistence of lamellae and a cubic Ia 3d structure over a narrow range of concentration and temperature. Several common behaviours are also revealed by comparison of different polymer blocks. With increasing concentration and temperature, ordered phases always appear in the order lamellar, cubic/PL, and hexagonal, although not all phases are observed in all materials. High concentration solutions (near 80 wt%) also undergo a re-entrant order–disorder transition to form nematic liquid crystalline phases, regardless of the polymer block chemistry.