Cooperative, reversible self-assembly of covalently pre-linked proteins into giant fibrous structures.

We demonstrate a simple bioconjugate polymer system that undergoes reversible self-assembling into extended fibrous structures, reminiscent of those observed in living systems. It is comprised of green fluorescent protein (GFP) molecules linked into linear oligomeric strands through click step growth polymerization with dialkyne poly(ethylene oxide) (PEO). Confocal microscopy, atomic force microscopy, and dynamic light scattering revealed that such strands form high persistence length fibers, with lengths reaching tens of micrometers, and uniform, sub-100 nm widths. We ascribe this remarkable and robust form of self-assembly to the cooperativity arising from the known tendency of GFP molecules to dimerize through localized hydrophobic patches and from their covalent pre-linking with flexible PEO. Dissipative particle dynamics simulations of a coarse-grained model of the system revealed its tendency to form elongated fibrous aggregates, suggesting the general nature of this mode of self-assembly.