Sequence-directed organization of beta-peptides in self-assembled monolayers.

The sequence-directed organization of self-assembled monolayers of amphiphilic beta-peptides adsorbed on gold surfaces is studied using Monte Carlo simulations. A phenomenological model is presented in which each (helical) molecule is represented by a rigid nanorod; side groups are placed at appropriate locations. This model can distinguish between globally amphiphilic (GA) and nonglobally amphiphilic (iso-GA) sequence isomers. The simulations show that the GA isomers have a high degree of orientational order that is not exhibited by the iso-GA isomers, which is consistent with experiment (Pomerantz et al. Chem. Mater. 2007, 19, 4436). The effect of surface coverage and relative strength of electrostatic, hydrophilic, and hydrophobic interactions on the self-assembly of beta-peptides is quantified.