Electrostatically-directed self-assembly of cylindrical peptide amphiphile nanostructures

We present theoretical studies of peptide amphiphile nanostructures created by Stupp and co-workers [Hartgerink, J. D.; Beniash, E.; Stupp, S. I. Science 2001, 294, 1684] and show that these amphiphiles exhibit attractive electrostatic interactions between their hydrophilic headgroups. These interactions prevail in their competition with the hydrophobic attraction between the amphiphile "tails" for the shape of the self-assembly, leading to cylindrical micelles of nanoscale dimension. The theory is supported by Monte Carlo simulations which show that in the absence of the directional electrostatic interactions between the headgroups the amphiphiles self-assemble into spherical micelles, in accord with our recent formal calculations [Tsonchev, S.; Schatz, G. C.; Ratner, M. A. Nano Lett. 2003, 3, 623], whereas inclusion of the electrostatic interactions leads to cylindrical nanostructures.