Photo-induced Morphological Changes of Lipid Bilayer Vesicles Enabled by a Visible-Light-Responsive Azo Compound

Living cells and organelles are separated by a lipid membrane bilayer. It is possible to induce morphological changes in this membrane by disturbing the order of the membrane using external stimuli and understanding the details of this mechanism is expected to be applicable to intracellular transport. DBA (DBAB-BODIPY-aminopropyl), which contains (1) a DBAB (4-[di(biphenyl-4-yl)amino]azobenzene) moiety that undergoes photo-isomerization under visible light irradiation, and (2) a BODIPY (borondipyrromethene) fluorophore was synthesized. The π-π* transition absorptions of both the azo moiety and that of BODIPY moiety in DBA were observed, independently. The photo-isomerization rate constant of the DMSO solution of DBA at 299K is 5.5 ×10^-3/s. The structure of the fluorescent group in DBA did not readily influence the isomerization. Upon introducing DBA into the lipid bilayer membranes of a vesicle suspension and irradiating the vesicles with visible light to isomerize the azo group, a morphological change in of the vesicles was observed due to the disturbance of the membrane order. Thus, DBA is a useful molecule for artificial modulation of the lipid membrane morphology.