| DAPI (4,6-diamidino-2-phenylindole) is a blue fluorescent dye that can penetrate cell membranes. The planar aromatic ring structure of DAPI complements the A-T rich regions of DNA, allowing the DAPI molecules to intercalate between the base pairs of the DNA double helix. When DAPI is not bound to DNA, it exists in a free state and exhibits almost no fluorescence. Upon binding to DNA, the molecular conformation of DAPI changes, and under ultraviolet excitation, it emits strong blue fluorescence (maximum excitation wavelength approximately 340 nm, emission wavelength approximately 488 nm). DAPI has a high affinity for double-stranded DNA and can specifically label cell nuclei. |
