Flip-Flop Movement of Phospholipids in 1,2-DimyristoyI-sn-glycero-3-phosphocholine/l,2-DihexanoyI-sn-glycero-3-phosphocholine Vesicles

摘要

Flip-flop movement was investigated via dithionite assay of l,2-dimyristoyl-sn-glycero-3-pho-sphoethanolamine-N-(7-nitro-2-1,3-benzoxadiazol-4-yl)(ammonium salt)(NBD-PE)fluorescence in 1,2-dimyristoyl-sn-glycero-3-phosphocholine/1,2-dihexanoyl-sn-glycero-3-phosphocholine(DMPC/DHPC)vesicles with different DMPC/DHPC ratios.The activation energy was determined by using the Arrhenius plot and the thermodynamic functions were determined by the transition state theory.The activation energy increased upon addition of DHPC into the DMPC bilayer,but all the changes of the thermodynamic functions did not show a similar tendency.The experimental results suggest that the DHPC inserted in DMPC bilayers promote the flip-flop movement of NBD-PE in DMPC/DHPC vesicles by disordering the transition state by shorter DHPC molecule.This phenomenon might be related to the increment of the accessibility of water molecules into the ground state of the vesicle bilayer.