A new monofluorinated phosphatidylcholine forms interdigitated bilayers

16-Fluoropalmitic acid was synthesized from 16-hydroxypalmiticacid using diethylaminosulfur trifluoride. This monofluorinated fatty acid then was used to make 1-palmitoyl-2-[16-fluoropalmitoyl]-phosphatidylcholine (F-DPPC) as a fluorinated analog of dipalmitoylphosphatidylcholine (DPPC). Surprisingly, We found that the phase transition temperature (T-m) of F-DPPC occurs near 50 degrees C, similar to 10 degrees C higher than its nonfluorinated counterpart, DPPC, as judged by both differential scanning calorimetry and infrared spectroscopy. The pretransition observed 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 esonance,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 hydrocarbon 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 interdigitated 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 inducing agents such as alcohols.