A C-NMR study of 10,12-tricosadiynoic acid and the corresponding phospholipid and phospholipid polymer

Diacetylene phospholipids are presently being studied because of their potential to polymerise in vesicles, multilayers and natural biomembranes. ¹³C-NMR spectra and spin-lattice relaxation times have now been obtained of a diacetylene phospholipid present in a sonicated dispersion in water. Similar data have been obtained of a monoacetylene phospholipid and a saturated phospholipid. For further comparison the spectrum of a diacetylenic fatty acid in benzene-d₆ was also examined and relaxation data obtained. A comparison of the various relaxation data provides an indication of the restricted motion associated with the two conjugated triple bonds of the diacetylene phospholipid within the lipid bilayer structure. A proximity interaction between diacetylene groups occurs and a conformation for the diacetylene part of the lipid in the bilayer is deduced. The ¹³C-NMR spectrum of a soluble phospholipid polymer in C²HCl₃, obtained by ultraviolet irradiation of the diacetylene phospholipid, shows that the two conjugated triple bonds of the monomer is replaced in the polymer by an alternating double and triple bonded conjugated structure.