[Nernst potential as a driving force of the fast transmembrane diffusion (flip-flop) of the anionic natural phospholipid phosphatidylethanol]

A unique rapid flip-flop of the naturally occurring negatively charged phospholipid phosphatidylethanol in sonicated phosphatidylcholine vesicles was studied using 13C NMR and phosphatidylethanol 13C-labeled at the CH2 ethyl moiety. The transbilayer diffusion of phosphatidylethanol was observed in response to the formation of Nernst potential (t 1/2 < 7 min), indicating that phosphatidylethanol transfer occurs in the anionic form. The application of the fluorescent potential-sensitive dye di-4-ANEPPS showed that the phosphatidylethanol movement across the membrane was accompanied by a decrease in the Nernst potential. In biological membranes, a facile spontaneous diffusion of phosphatidylethanol implies the lack of high asymmetry of its distribution, even if phosphatidylethanol is synthesized exclusively on one side of the membrane.