ASSESSMENT OF THE C-525 LASER-DYE AS A CHEMILUMINESCENCE SENSITIZER FOR LIPID-PEROXIDATION IN BIOLOGICAL-MEMBRANES - A COMPARISON WITH CHLOROPHYLL-A

The C-525 laser dye at micromolar concentration range is shown to enha nce up to two to three orders of magnitude the chemiluminescence (CL) accompanying tert-butyl hydroperoxide (I-BHP)-induced rat liver micros ome oxidation and Fe2+-induced lipid peroxidation (LPO) in liposomes. C-525 is shown to be a more efficient sensitizer of CL accompanying LP O in membrane systems than the known low-energy excited tripler carbon yl sensitizer, chlorophyll-a, (C1-a). Regarding the sensitization mech anism, C-525 and C1-a were compared in (a) a peroxyl radical-producing system (2,2'-azobis(2-dimethylvaleronitrile) (AMVN); (b) excited carb onyl-producing systems (3-hydroxymethyl-3,4,4-trimethyl-1,2-dioxetane (HTMD) thermal decomposition and horseradish peroxidase (HRP)-catalyze d isobutanal oxidation); and (c) excited singlet oxygen-producing syst em [endoperoxide of 3,3-(1,4-naphthylidene)-dipropionate (NDPO2)]. C-5 25 sensitized CL only in the systems where peroxyl radical and/or trip let excited carbonyls are produced; the mechanism of CL sensitization apparently is energy transfer from the excited triplet carbonyls forme d in the peroxyl radical self-reaction via Russell's mechanism or by d ioxetane decomposition. C1-a was found to considerably sensitize CL re lated to NDPO2 thermal decomposition, a source of singlet oxygen, in a ddition to acting as a sensitizer of tripler carbonyl CL. The chemical stability of the C-525 laser dye in excited state-generating systems was shown to be appropriate for its application as a sensitizer of CL related to LPO reactions in membranes, but not in the HRP-catalyzed pe roxidation system.