title: Gamma-irradiation damage to liposomes differing in composition and their protection by nitroxides.
abstract: The present study aims to determine the effect of bilayer composition on oxidative damage and the protection against it in lipid multicomponent membranes. Irradiation damage in 200-nm liposomes and the protection provided by the nitroxide radicals, 2,2,6,6-tetramethylpiperidine-1-oxyl (Tempo) and 4-hydroxy-2,2,6,6-tetramethylpiperidine--1-oxyl (Tempol) were assessed by monitoring several chemical and physical parameters. Liposomes were prepared in four different lipid compositions (mole ratios), DPPC:DPPG 10:1; DPPC:DPPG:cholesterol 10:1:4; EPC:EPG 10:1; and EPC:EPG:cholesterol 10:1:4, and gamma-irradiated with a dose of 32 kGy. Lipid degradation was determined by HPLC and GC analyses, whereas size and differential scanning calorimetry measurements were used to monitor physical changes in the liposomal dispersions. The results indicate that: (1) addition of 5 mM Tempo or Tempol, or freezing of the sample inhibited radiation-induced lipid degradation; (2) Tempo and Tempol caused neither physical nor chemical changes in the liposomal dispersions; and (3) both nitroxides prevented or reduced some of the radiation-induced changes in thermotropic characteristics of the liposomes, preventing a shift in the temperature of the maximum of the main phase transition.
authors.affiliation: Department of Biochemistry, Hebrew University-Hadassah Medical School, Jerusalem, Israel.
authors.forename: A M
authors.initials: AM
authors.lastname: Samuni
authors.forename: Y
authors.initials: Y
authors.lastname: Barenholz
authors.forename: D J
authors.initials: DJ
authors.lastname: Crommelin
authors.forename: N J
authors.initials: NJ
authors.lastname: Zuidam
mesh_terms: D000215:Acylation; D015925:Cryopreservation; D003497:Cyclic N-Oxides / Q000494:pharmacology*; D005609:Free Radicals; D005720:Gamma Rays; D006863:Hydrogen-Ion Concentration; D015227:Lipid Peroxidation; D008081:Liposomes; D010743:Phospholipids / Q000528:radiation effects; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D013113:Spin Labels
chemical_list: D003497:Cyclic N-Oxides; D005609:Free Radicals; D008081:Liposomes; D010743:Phospholipids; D011837:Radiation-Protective Agents; D013113:Spin Labels; C001803:tempol; C003959:TEMPO