BP Fluor 405 (Alexa Fluor 405 Equivalent; AF405) is a water-soluble, blue-fluorescent dye that is often used in multi-color applications, including flow cytometry and super-resolution microscopy using STORM. Its excitation is ideally suited for the 407 nm spectral line of the krypton laser or the 408 nm violet laser diode. BP Fluor 405 conjugates are pH-insensitive from pH 4 to pH 10.