Structural Modifications Induced by Violacein in Lipid Membranes*

Several gram negative bacteria produce a purple pigment called violacein which helps them to protect against the surrounding gram positive bacteria. Violacein possesses a high affinity towards the lipid membrane and understanding their interaction mechanism can help in facilitating the use of violacein in the pharmaceutical paradigm. The present study sheds light on the surface and structural modifications induced by violacein in zwitterionic, cationic, and anionic lipid membranes. The modified surface activity of lipid monolayers with the addition of violacein was manifested as change in transition temperature and in-plane elasticity. Increment in membrane thickness with the addition of violacein to zwitterionic and cationic lipid monolayers was confirmed from x-ray reflectivity measurements. Grazing incidence x-ray diffraction study on lipid multilayers suggests a decrease in lattice parameters and tilt angle confirming the increased compactness of the mixed system.