16-Fluoropalmitic acid was synthesized from 16-hydroxypalmiticacid usi
ng diethylaminosulfur trifluoride. This monofluorinated fatty acid the
n was used to make lmitoyl-2-[16-fluoropalmitoyl]-phosphatidylcholine
(F-DPPC) as a fluorinated analog of dipalmitoylphosphatidylcholine (DP
PC). Surprisingly, We found that the phase transition temperature (T-m
) of F-DPPC occurs near 50 degrees C, similar to 10 degrees C higher t
han its nonfluorinated counterpart, DPPC, as judged by both differenti
al scanning calorimetry and infrared spectroscopy. The pretransition o
bserved for DPPC is absent in F-PPC. A combination of REDOR, (r) under
bar otational-(e) under bar cho <(do)under bar>uble-(r) under bar eso
nance,an conventional solid-state N-MR experiments demonstrates that F
-DPPC forms a fully interdigitated bilayer in the gel phase. Electron
paramagnetic resonance experiments show that below T-m, the hydrocarbo
n chains of F-DPPC are more motionally restricted than those of DPPC.
X-ray scattering experiments confirm that the thickness and packing of
gel phase F-DPPC is similar to that of heptanetriol-induced interdigi
tated DPPC. F-DPPC is the first phosphoglyceride containing sn-l: and
sn-2 ester-linked fatty acyl chains of equal length that spontaneously
forms interdigitated bilayers in the gel state in the absence of indu
cing agents such as alcohols.