Photo- and thermo-responsive assembly of liposomal membranes triggered by a gemini peptide lipid as a molecular switch

A gemini peptide lipid composed of l-histidyl residues, hydrophobic double-chain segments, and an azobenzene spacer unit was synthesized as a photoresponsive molecular switch for assembly of liposomal membranes. Photoisomerization of the azobenzene moiety between the trans-form and the corresponding cis-form reversibly proceeded in the liquid crystalline state of the liposome formed with phospholipids, but not in the gel state below the phase transition temperature. The gemini peptide lipid with the cis-azobenzene spacer recognized Cu2+ ions to induce vesicular assembly in the liquid crystalline state of the liposomal membrane. On the other hand, the corresponding trans-form, which exhibited little affinity toward Cu2+ ions, did not act as a molecular switch for vesicular assembly. Furthermore, photo-switching behavior performed by the gemini peptide lipid was tuned using the thermotropic phase transition of the matrix membrane.