The uptake of pristane (2,6,10,14-tetramethylpentadecane) into phosphilipid bilayers as assessed by NMR, DSC, and tritium labeling methods

Abstract

Unilamellar dioleoylphosphatidylcholine (DOPC) liposomes (250 μM) incorporated 2 mol% of [ 3H]pristane at 37°C after addition of 50 μM pristane solubilized with β-cyclodextrin. Conventional solubilization in dimethyl sulphoxide resulted in much lower uptake. Premixing of perdeuterated pristane with DOPC and dipalmitoylphosphatidylcholine (DPPC) prior to the formation of multilamellar liposomes resulted in homogeneous incorporation of up to 5 mol% pristane at 22°C and 50°C, respectively, as observed by 2H-NMR. Lipid order parameters measured by 31P and 2H-NMR remained unchanged after pristane uptake. Pristane induced the transformation of part of the dioleoyphosphatidylethanolamine (DOPE)/DOPC (3:1, mol/mol) liquid crystalline lamellar phase into an inverse hexagonal phase. 5 mol% pristane in DPPC bilayers decreased the midpoint of the main phase transition temperature of DPPC from 41.5°C to 40.9°C. Upon cooling in the temperature range from 41°C to 36°C, pristane was either displaced from the DPPC bilayer or the mode of incorporation changed. These results may aid in defining the mechanisms whereby pristane, an isoprenoid C 19-isoalkane, induces plasmacytomagenesis in mice.