Sequence effects on peptide assembly characteristics observed by using scanning tunneling microscopy.

Homogeneous assemblies of the model peptides at interfaces have been achieved and observed with scanning tunneling microscopy. The dependence of the observed brightness in STM images is analyzed, and the correlation with the peptide residues is proposed. We have also investigated the conformational dynamics of the peptide assemblies adsorbed on a graphene sheet by performing all-atom molecular dynamic simulations in water at 300 K. The simulation results of the two peptide assemblies on graphite surfaces show that R(4)G(4)H(8) and F(4)G(4)H(8) peptide assemblies are mostly in β-sheet structure, and the interaction energy of the four different residues with graphite surfaces follows the order of Phe > His > Arg > Gly, consistent with their brightness contrasts in STM images. The insight on the distribution of residue moieties in the peptide assemblies could provide beneficial venues for studying peptide-based interfacial processes such as site-specific interactions between molecular species with peptides.