CONFORMATIONAL-CHANGES OF MELITTIN UPON INSERTION INTO PHOSPHOLIPID MONOLAYER AND VESICLE

Two model systems were used to study the conformational changes of mel ittin upon insertion into phospholipid. The first model system is phos pholipid monolayers with different surface pressure. The second one is small unilamellar vesicles at above or below their phase transition t emperature. The conformational changes of melittin upon insertion were elucidated by employing a combination of monolayer technique, fluores cence technique, CD, and FTIR. The results showed that melittin adsorb ed on the lipid layer surface contains less alpha-helix than its count erpart inserted into the lipid layer. As the penetration depth of meli ttin increases, more ordered structures (alpha-helix) appear. A possib le molecular mechanism underlying melittin insertion is proposed.