THE SENSITIZATION OF FE2-INDUCED CHEMILU MINESCENCE IN HUMAN BLOOD-PLASMA LOW-DENSITY LIPOPROTEINS BY C-525 FLUORESCENCE DYE()

The effect of the fluorescent dye H,4H-tetrahydro-9-(2'-benzoimidazoly l)-quinolizin- (9,9a,l-gh) coumarin (C-525) on the chemiluminescence ( CL) flash kinetics accompanying Fe2+-induced Free radical lipid hydrop eroxide decomposition in low density lipoproteins (LDL) have been stud ied. C-525 was found to increase CL flash intensity by a factor of mor e than 2000 at the concentration of 4 mkM without any influence on the CL kinetics. The mechanism of the CL amplification is apparently ener gy transfer from the primary excited product of lipid peroxyl radical recombination to fluorescent level of the C-525. A concentration depen dencies of CL amplification degree by C-525 on the LDL concentration w ere revealed to be bell-shaped, so that for 0,01 mg/ml of LDL protein the maximum amplification degree was observed at 4 mkM of C-525, where as for 0,02 mg/ml of LDL - at 8 mkM. For the elucidation of these effe cts the properties of C-525 as hydrophobic fluorescent probe have been used. The concentration dependencies of C-525 fluorescence in the LDL suspension were found to be similar to that of CL amplification by C- 525. These data pointed to the fact that concentration dependencies of the CL amplification hy C-525 was conditioned by its accumulation in a hydrophobic phase of lipoproteins, so that the effective dye concent ration was determined by both the amount of C-525 added tb the suspens ion and the concentration of LDL.