Radiation-induced fragmentation of cardiolipin in a model membrane

Purpose : To obtain evidence for the possibility of free-radical fragmentation of cardiolipin under the action of ionizing radiation as measured by its aqueous dispersion from liposomes. Materials and methods : Liposomes of tetramyristoylcardiolipin (TMCL) were exposed to gamma -rays from 60 Co or 137 Cs sources at doses between 1 and 24 kGy. Fragmentation products were identified using thin-layer chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Results : Using MALDI-TOF MS and thin-layer chromatography, it was shown that gamma -irradiation of liposomes consisting of TMCL was accompanied by free-radical fragmentation of the lipid to form dimiristoylphosphatidic acid and dimiristoylphosphatidyl hydroxyacetone. The yields of dimiristoylphosphatidic acid were greater than those of dimiristoylphosphatidyl hydroxyacetone, and formation of the named compounds was inhibited by dissolved oxygen. Conclusion : It is shown for the first time that on gamma -irradiation, cardiolipin can undergo free-radical fragmentation in its polar component.