This is a necessary consequence of it intercalating a week rather than a day. It acts as a topoisomerase II poison and intercalating agent. Interior cells of the blastoderm move towards the outer cells, thus "intercalating" with each other. It is added to running buffer and binds by intercalating between DNA base pairs. DNA damage occurs constantly because of chemicals (e.g. intercalating agents), radiation and other mutagens. Ligands may interact with DNA by covalently binding, electrostatically binding, or intercalating. Doxorubicin interferes with cell growth and replication by intercalating in DNA. PI binds to DNA by intercalating between the bases with little or no sequence preference. Similarly to other anthracyclines, epirubicin acts by intercalating DNA strands. Propidium iodide is a fluorescent intercalating agent that can be used to stain cells.