Interaction of phospholipid liposomes with a DNA model compound in irradiated systems

Phospholipid liposomes of different unsaturated fatty acid compositions were irradiated either in the presence of a double-stranded polynucleotide, or alone and then mixed with the polynucleotide. Changes in the structure of the polynucleotide were estimated by measuring its ability to form a fluorescent intercalation complex with ethidium bromide. The results imply that radiation-induced peroxidation of the polyunsaturated fatty acids of the phospholipid followed by transfer of damage to the polynucleotide was a very minor process in these systems. The results are discussed in terms of .OH radical attack on the phospholipids at the polar head group or at saturated positions of the fatty acid chains near the water lipid interface. The intermediates produced by this process may then damage the polynucleotide.