Sulfate ion-triggered self-assembly transitions of amphiphilic short peptides by force balance adjustment

Abstract

The divalent sulfate ion (SO42-) was found to effectively modulate the self-assembly behaviors of three amphiphilic peptides with similar structural feature but varied sequence, that is, A6K, A9K and I3K, by modulating the force balance during the self-assembly process. Intervening of SO42- with peptide self-assembly resulted in distinct morphology changes of the self-assembled structures depending on the peptide molecular hydrophobicity and the stability of the self-assembled structures. New structures were produced in the cases of A6K and A9K, while no obvious structural change was found for I3K. However, one common feature for the three cases was that the lateral association propensity was greatly enhanced by salt addition. The underlying mechanism should be that the salt ions modulate effectively the balance between different driving forces for self-assembly, that is, electrostatic interaction, hydrophobic interaction and hydrogen bonding, which trigger change of the self-assembly route to produce new structures. The study provides new insights into the specific ion effects and paves new ways for modulating the peptide self-assembly to control precisely the self-assembled structures.