Self-assembly of amphiphilic peptide (AF)6H5K15 derivatives: roles of hydrophilic and hydrophobic residues.

A molecular dynamics simulation study is reported to investigate the roles of hydrophilic and hydrophobic residues in the self-assembly of (AF)6H5K15 peptide derivatives. The peptide, as well as water and counterions, are represented by the MARTINI coarse-grained model. The assembly is observed to follow a three-step process: formation of small clusters, large clusters, and micelles. With increasing length of hydrophilic Lys residues in (AF)6H5Kn (n = 10, 15, 20, and 25), assembly capability is found to be reduced with the formation of smaller micelles or the presence of individual peptide chains. Upon replacing Ala by more hydrophobic Phe in AmFnH5K15 (m + n = 12), larger micelles are formed. With increasing length of hydrophobic Phe residues in FnH5K15 (n = 4, 8, 12, and 16), micelle size increases and the morphology shifts from spherical to fiber-like. The simulation study provides mechanistic insight into the crucial roles of hydrophilicity and hydrophobicity in the assembly of (AF)6H5K15 derivatives; it reveals that assembly capability is reduced by increasing hydrophilicity, whereas increasing hydrophobicity leads to morphology transition.