Lysine-based chiral vesicles.

Uni-lamellar and multi-lamellar vesicles were prepared by the enantiomers of a biological molecule, L-lysine or D-lysine, with a double-tail weak monoacid, di-(2-ethylhexyl) phosphoric acid (abbreviated as DEHPA), in water. With the addition of DEHPA to lysine aqueous solutions, ion-pairs are formed through the acid-base reaction between the lysine cations and DEHP(-) anions. The self-assembled vesicles were proved to be driven by the hydrogen bonding between the side-chain amino groups in lysine molecules and the polar groups of DEHP(-) species. The combination of DEHPA and lysine through electrostatic interactions and hydrogen bonding reduces the cross-sectional area of the hydrophilic groups, improving the surface activity and inducing a microstructural transition from primitive aggregates to micelles, and to vesicles in solution. Due to the chirality of the lysine molecules, the aggregates exhibited diverse chiral properties along with the microstructural transitions.