Measurement of Blue Fluorescence as a Protein Marker for Oxidized Membranes

Fluorescence generated in living cells has been referred to as an age-related lipofuscin-like substances and also an index of aging (1 ,2 ). Cells and tissues contain three kinds of fluorescence: yellow, green, and blue. Among them, yellow fluorescence that fluoresced at around 620 nm is regarded as an agerelated lipofuscin observed histochemically under microscope. Although yellow fluorescent pigment was regarded in the past as the products between proteins and lipid peroxidation products, it is not likely that the pigment is derived from lipid peroxidation (3 ). Green fluorescence that fluoresced at around 520 nm is due to flavin-containing components. Blue fluorescence that fluoresced at around 450 nm is believed to be derived from the reaction of proteins with lipid peroxidation products in living cells in situ (4 ).