Use of Coiled-Coil Domains to Direct the Self-Assembly of Protein-Polymer Conjugates

Protein-polymer conjugates have been demonstrated to greatly enhance protein activity and sensitivity in catalytic and biosensing applications. To achieve this enhanced biosensor sensitivity, however, it is critical that the conjugates self-assemble into well-defined nanostructures. In this study, strongly associating coiled-coil domains are added to the protein block of protein-polymer conjugates to promote self-assembly. One of the two constituent alpha helices of a heterodimeric coiled-coil is appended to either the N- or C-terminus of a binding protein previously demonstrated to exhibit weak ordering. Small-angle X-ray scattering (SAXS) measurements indicate that homogeneous solutions of the conjugates containing a single coiled-coil domain generally self-assemble as weakly as the unmodified binding protein. When one of these conjugates is combined in a molar ratio with another conjugate containing the other alpha helix in the coiled-coil heterodimer, though, well-defined nanostructures are formed with SAXS peak full width at half maximum (FWHM) values 2- to 4-fold smaller than those for the bare binding protein.