Hydrogen abstraction from lipids by triplet states of derivatized benzophenone photosensitizers

Laser photolysis techniques have been used to characterize the reactivity of triplet state lipoidal benzophenone derivatives toward fatty acids and glycerides in benzene solution. The reactivities of benzophenone-4-heptyl-4'-pentanoic acid (BHPA) toward fatty acid compounds having different configurations of olefinic bonds have been determined. The rates of hydrogen abstraction are found to be lower when compared with similar measurements using benzophenone alone. However, the contribution of physical quenching of the triplet derivative by double bonds also appears to be slightly lower than that found with benzophenone itself. The hydrogen abstraction efficiencies of three other benzophenone derivatives toward linoleic acid in benzene have also been measured. For benzophenone incorporated into a fatty acid molecule, there is a limited relationship between structure and photoreactivity. Finally, these sensitizers have been incorporated into mixed SDS/linoleate micelles to determine the effects of molecular organization on photochemical behavior of the sensitizer and lipid.