Membrane Thinning Effect of Curcumin

Interaction of curcumin with lipid bilayers is not well understood. A recent experiment showed that curcumin significantly affected the single channel lifetime of gramicidin in a DOPC bilayer without affecting its single channel conductance. We performed two experiments in order to understand this result. By isothermal titration calorimetry, we measured the partition coefficient of curcumin binding to DOPC bilayers. By X-ray lamellar diffraction, we measured the thickness change of DOPC bilayers as a function of curcumin-lipid ratio. A non-linear membrane thinning effect by curcumin was discovered. The gramicidin data were qualitatively interpreted by the combination of ITC and X-ray results. We show that curcumin not only thins the lipid bilayer, it might also weaken its elasticity moduli. The result implies that curcumin may affect the function of membrane proteins by modifying the properties of the host membrane. 10.1529/biophysj.107.126888