Abstract
The dipole potential generating an electric field much stronger than any other type of membrane potential influences a wide array of phenomena, ranging from passive permeation to voltage-dependent conformational changes of membrane proteins. It is generated by the ordered orientation of lipid carbonyl and membrane-attached water dipole moments. Theoretical considerations and indirect experimental evidence obtained in model membranes suggest that the dipole potential is larger in liquid-ordered domains believed to correspond to lipid rafts in cell membranes. Using three different dipole potential-sensitive fluorophores and four different labeling approaches of raft and nonraft domains, we showed that the dipole potential is indeed stronger in lipid rafts than in the rest of the membrane. The magnitude of this difference is similar to that observed between the dipole potential in control and sphingolipid-enriched cells characteristic of Gaucher's disease. The results established that the heterogeneity of the dipole potential in living cell membranes is correlated with lipid rafts and imply that alterations in the lipid composition of the cell membrane in human diseases can lead to substantial changes in the dipole potential.
Highlights
The dipole potential generating an electric field much stronger than any other type of membrane potential influences a wide array of phenomena, ranging from passive permeation to voltage-dependent conformational changes of membrane proteins
As the dipole potential drops over a very short distance (2 and 3 nm, the approximate thickness of the monolayers in a bilayer) through the low dielectric hydrophobic interior of a membrane, it results in a large electrostatic dipole electric field that a variety of experimental and computational techniques have estimated to be in the range of 108– 109 V/m
On the basis of the correlation between the dipole potential reported by three different, ratiometric, dipole potential-sensitive dyes and the distribution of lipid rafts labeled by cholera toxin (CTX)-B, GPI-anchored green fluorescent protein (GFP), or an anticholesterol antibody, we show that the dipole potential is significantly larger in lipid rafts than in the rest of the membrane
Summary
The dipole potential generating an electric field much stronger than any other type of membrane potential influences a wide array of phenomena, ranging from passive permeation to voltage-dependent conformational changes of membrane proteins. As the dipole potential drops over a very short distance (2 and 3 nm, the approximate thickness of the monolayers in a bilayer) through the low dielectric hydrophobic interior of a membrane, it results in a large electrostatic dipole electric field (which is the spatial derivative of the potential) that a variety of experimental and computational techniques have estimated to be in the range of 108– 109 V/m This is significantly larger than either of the other two electrostatic fields associated with the transmembrane and surface potentials (estimated to be around 2.5 · 107, and 106 V/m, respectively) [1,2,3,4,5]. That the extent of these effects depends on whether the proteins are localized in or outside of lipid rafts [12]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
