Benzophenone-Sensitized Peroxidation in Compressed Lipid Monolayers at Air-Water Interface

The paper reports on a study of radical-type lipid peroxidation of biomembrane lipid constituents in compressed monolayers, with incorporated lipoidic benzophenone photosensitizers. Their triplets abstract allylic and double-allylic hydrogen atoms from hydrophobic moieties of the lipid molecules. The results confirmed the H abstraction occurrence (and thus the initiation of the peroxidizing chain mechanism), and absence of lipid peroxide formation at the same time. The reason is in the "cage effect": highly restricted spatial area of compressed lipid monolayers limits mobility of the formed radicals (lipid and ketyl radicals) and leads to their recombination, preventing the propagation step of the chain mechanism. With certain approximation, one may conclude that these results have clear implication for real biomembranes: their structure is one of the main factors in prevention of spreading of the chain reaction, and lipid peroxide formation.