Self-assembly of mastoparan X derivative having fluorescence probe in lipid bilayer membrane

A mastoparan X (MPX) derivative having an anthryl group at the C-terminal residue was synthesized (MPX-A), and its conformation, orientation and aggregation in phospholipid bilayer membrane were studied. The efficiency of intramolecular energy transfer from the Trp residue to the anthryl group at high peptide dilution suggested alpha-helical conformation in the lipid membrane, which is consistent with the previous report by NMR of MPX concentrated in the membrane. Either emission from the Trp residue or the anthryl group of MPX-A in the lipid membrane was quenched by 5-doxylstearic acid, suggesting that MPX-A is located at the membrane surface with the helix axis oriented parallel to the surface. The dependence of the excited energy transfer and the fluorescence depolarization of MPX-A on the peptide concentration revealed that MPX-A aggregated in the lipid membrane to form a defined structure.