The dye 3‐(4‐(N,N‐dimethylamino)phenyl)naphtho[1,2‐b]quinolizinium was synthesized by means of a Suzuki–Miyaura reaction in good yield, and its binding properties with duplex DNA, quadruplex DNA (G4‐DNA), RNA, and bovine serum albumin (BSA) were investigated by photometric, fluorimetric and polarimetric titrations and DNA denaturation analysis. The compound intercalates into DNA and RNA, associates in binding site I of BSA, and binds to G4‐DNA by terminal π stacking. The ligand exhibits a fluorescence light‐up effect upon complexation to these biomacromolecules, which is more pronounced and blue shifted in the presence of BSA (Φfl=0.29, λfl=627 nm) than with the nucleic acids (Φfl=0.01–0.05, λfl=725–750 nm). Furthermore, the triple‐exponential fluorescence decay of the probe when bound to biomacromolecules in a cell enables their visualization in this medium and the differential labeling of cellular components.

Induction of terminal erythroid differentiation can be an efficient strategy to inhibit proliferation of chronic myelogenous leukemia cells. Psoralens, well-known photo-chemotherapeutic agents, were found to be efficient at inducing erythroid differentiation of K562 cells, an in vitro cell line isolated from the pleural effusion of a patient with chronic myelogenous leukemia in blast crisis. The effects of crude pre-irradiated solutions of 5-methoxypsoralen on erythroid differentiation of human leukemic K-562 cells were evaluated. The major photoproduct was characterized and analyzed, and it was found to induce erythroid differentiation of K562 cells and inhibit NF-kappaB/DNA interactions.