Effect of phase transitions in hydrated 1,2-dipalmitoylphosphatidylethanolamine bilayers on the spin probe order parameter

Phases and phase transitions of the hydrated phosphatidylethanolamines

LIPIDAT is a computerized database providing access to the wealth of information scattered throughout the literature concerning synthetic and biologically derived polar lipid polymorphic and mesomorphic phase behavior. Here, a review of the LIPIDAT data subset referring to hydrated phosphatidylethanolamines (PE) is presented together with an analysis of these data. The PE subset represents 14% of all LIPIDAT records. It includes data collected over a 38-year period and consists of 1511 records obtained from 203 articles in 35 different journals. An analysis of the data in the subset has allowed us to identify trends in synthetic PE phase behavior reflecting changes in lipid chain length, chain unsaturation (number, isomeric type and position of double bonds), chain asymmetry and branching, type of chain-glycerol linkage (ether vs. ester) and headgroup modification. Also included is a summary of the data concerning the effect of pH, stereochemical purity, and different additives such as salts, saccharides, alcohols, amino adds and alkanes on PE phase behavior. Information on the phase behavior of biologically derived PE is also presented. This review includes 236 references.

Lipid peroxidation of phosphatidylcholine liposomes depressed by the calcium channel blockers nifedipine and verapamil and by the antiarrhythmic-antihypoxic drug stobadine

Nifedipine, verapamil and stobadine were tested and compared with butylated hydroxytoluene (BHT) as possible free radical scavengers inhibiting lipid peroxidation in phosphatidylcholine liposomes. Liposomes were peroxidized by incubation in air at 50 degrees C. Verapamil less than nifedipine less than BHT less than stobadine depressed the lipid peroxidation as detected spectroscopically for conjugate diene and thiobarbituric acid product formation. Verapamil and stobadine were tested as OH radical scavengers in a Fenton-type reaction against spin trap 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO), as detected by ESR spectroscopy. The tested drugs competed with DMPO in trapping OH radicals, with stobadine being more effective than verapamil. ESR spectra of nifedipine in the incubated liposomes revealed that nifedipine could be involved in free radical reactions in the liposomes leading to nifedipine-stable radical(s) which were immobilized in the membrane. The obtained results suggest that some of the beneficial effects of the studied drugs can be mediated in disease by their ability to scavenge free radicals and by their protective effect on lipid peroxidation.