Microscopical and spectroscopic studies on the fluorescence of a daunomycin-aluminum complex

In this study, the spectroscopic features and microscopical applications of the fluorescent daunomycin-Al3+ complex have been analyzed. In the presenc e of Al3+, the absorption spectrum of daunomycin showed a deep bathochromic shift and new peaks at 529 and 566 nm, whereas the fluorescence emission w as considerably modified. The emission of daunomycin alone (peak at 560 nm under optimal excitation at 470 nm) decreased continuously from 0.5 to 24 h after addition of Al3+ ions, and a new emission peak appeared at 580 nm (o ptimal excitation at 530 nm). Under the fluorescence microscope using green exciting light, nuclei from chicken blood smears and paraffin sections of rat embryos stained with daunomycin showed a weak emission, which greatly i ncreased after treatment with Al3+ ions. The bright and stable fluorescence of chromatin DNA induced by daunomycin-Al3+ could be a valuable labelling method in fluorescence microscopy and DNA cytochemistry.