Partitioning of a fluorescent phospholipid between fluid bilayers: dependence on host lipid acyl chains.
The partition coefficient Kp was measured for a headgroup-labeled phospholipid (12:0,12:0)-N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)-PE (12-NBD-PE), equilibrated between LUV of a series of phosphatidylcholines (PC). Fluorescence resonance energy transfer between the 12-NBD-PE and a headgroup-rhodamine-labeled PE was used to find the equilibrium concentration of the 12-NBD-PE in the different LUV. Reliable equilibrium concentrations were obtained by monitoring the approach to equilibrium starting from a concentration below and from a concentration above the ultimate values. Using (16:0,18:1delta9)-PC as the reference lipid, Kp ranged from a high value of 1.65 favoring (16:0,18:1delta9)-PC over (16:1delta9,16:1delta9)-PC, to a low value of 0.90, favoring (22:1delta13,22:1delta13)-PC over (16:0,18:1delta9)-PC. The Kp values enabled calculation of the acyl chain contribution to the excess free energy of mixing for (12:0,12:0) acyl chains at infinite dilution in the L alpha phase of PC having acyl chains of (16:0,18:1delta9), (16:1delta9,16:1delta9), (18:1delta9,18:1delta9), (18:1delta6,18:1delta6), (20:1delta11,20:1delta11), and (22:1delta13,22:1delta13). (14:1delta9,14:1delta9)-PC was found to transfer so rapidly between LUV as to preclude reliable Kp measurement.
Feigenson
G W
GW
Section of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, New York 14853, USA. gwf3@cornell.edu
D055592:Biophysical Phenomena; D001703:Biophysics; D004735:Energy Transfer; D005456:Fluorescent Dyes / Q000737:chemistry; D008051:Lipid Bilayers / Q000737:chemistry*; D008956:Models, Chemical; D010714:Phosphatidylethanolamines / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry*; D015203:Reproducibility of Results; D013816:Thermodynamics
D005456:Fluorescent Dyes; D008051:Lipid Bilayers; D010714:Phosphatidylethanolamines; D010743:Phospholipids; C042077:N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)phosphatidylethanolamine