Self-assembly of alpha-helical coiled coil nanofibers.

The alpha-helical coiled coil is one of the best-studied and most well-understood protein folding motifs. In particular, the coiled coil can be made to self-assemble into a nanofibrous architecture with many potential applications in biomimetic engineering and elsewhere. The key to the assembly of such nanofibers has been the formation of "sticky ended" dimers through careful selection of electrostatically charged amino acids. In this work, we demonstrate for the first time that sticky ended dimers are not a prerequisite for alpha-helical coiled coil nanofiber formation. In contrast, we show that blunt-ended dimers are able to form nanofibers with a uniform diameter of 4 nm while being hundreds of nanometers in length. Furthermore, the length and lateral packing can be controlled through selection of amino acids not involved in the coiled coil interface.