Incorporation of bacitracin in Langmuir films of phospholipids at the air-water interface

Properties of microbicide drugs are believed to be associated to their interactions with biointerfaces such as cell membranes, encouraging research on the identification of membrane sites capable of drug binding. In this study, we investigated the interaction of bacitracin, a known antibiotic peptide, with cell membrane models represented by Langmuir monolayers of selected phospholipids. It is shown that even small amounts of bacitracin affect the surface pressure-area isotherms, as well as the vibrational spectra and the morphology of phospholipid monolayers, which points to a specific interaction for each phospholipid. Such effects depend on the chemical nature of the monolayer-forming molecules, with the drug activity being distinctive for dipalmitoyl-sn-glycero-3-phospho-l-serine sodium salt in contrast to what was observed for 1,2-dipalmitoyl-sn-glycero-3-phospho-l-choline and 1,2-dipalmitoyl-sn-glycero-3-phospho-(1′-rac-glycerol) sodium salt. As a result, the phospholipid composition of the monolayer modulates the interaction with the peptide, which may have important implications in understanding how the drug acts on specific sites of cell membranes.