Conformational changes of melittin upon insertion into phospholipid monolayer and vesicle.

Two model systems were used to study the conformational changes of melittin upon insertion into phospholipid. The first model system is phospholipid monolayers with different surface pressure. The second one is small unilamellar vesicles at above or below their phase transition temperature. The conformational changes of melittin upon insertion were elucidated by employing a combination of monolayer technique, fluorescence technique, CD, and FTIR. The results showed that melittin adsorbed on the lipid layer surface contains less alpha-helix than its counterpart inserted into the lipid layer. As the penetration depth of melittin increases, more ordered structures (alpha-helix) appear. A possible molecular mechanism underlying melittin insertion is proposed.