Anomalous flip-flop of DMPC in lipid membranes

Although the study of the passive movement of lipids between and within membranes can give insight into lipid transport regulation by providing a way to gauge the energetic cost on active metabolic pathways, published work on the spontaneous transfer of lipids report a wide variation in the rates of transfer between and particularly within membranes. Non-invasive approaches like time resolved small angle neutron scattering or sum -frequency vibrational spectroscopy have shown that the movement of lipids is extremely sensitive to chemical structures of molecules finding that the transfer rates of unaltered lipid molecules are dramatically different from their chemically tagged counterparts. My group performed Neutron Scattering experiment and found that DMPC flip-flop rates display two Arrhenius states well above DMPC’s melting temperature. I will report on measurements of the flip-flop rates in DMPC using nuclear magnetic resonance spectroscopy and membrane order and fluidity using Laurdan generalized polarization, DPH anisotropy respectively, to reveal the nature of this intriguing behavior.