Fluorescence energy transfer studies on normal and leukemic mouse lymphocytes.

Control and acute leukemic cells of AKR:Lac C3H mg:Lac/F1 hybride mice were labeled either with ethidium bromide or ethidium bromide plus fluorescamine. Theoretical and experimental evidence shows that the ethidium bromide binding ability of cells and the average efficiency of Förster-type fluorescence energy transfer between fluorescamine and ethidium bromide inside the cells depend on both the cell and dye concentrations. It is shown further that fluorescamine treatment enhances the uptake of ethidium bromide by both normal and leukemic cells. A sevenfold difference was found in ethidium bromide binding ability between normal and leukemic cells at optimal dye concentration.