Spectrofluorometric studies of nile red treated native and oxidized low density lipoprotein.

1. The excitation and emission maxima of nile red in the presence of LDL were found to be 526 and 587 nm, respectively. Oxidation of LDL for 16 hr in the presence of CuSO4 resulted in significant spectral shifts to longer wavelengths in both the excitation and emission spectra. 2. The difference in the fluorescence intensity between native and oxidized LDL was most pronounced at wavelengths between 550 and 580 nm. At these emission wavelengths, the relative fluorescence intensity of nile red treated oxidized LDL was found to be decreased by approx 30% when compared to that observed in the presence of native LDL. 3. Differences in the nile red fluorescence spectra were not observed when LDL and acetylated LDL were compared.