Alexa Fluor 405 succinimidyl ester is an amine-reactive derivative of our Cascade Blue dye, which was previously only available as an acetyl azide. Alexa Fluor 405 conjugates exhibit excitation/emission maxima of 401/421 nm, making them a near-perfect match to the 407 nm spectral line of the krypton laser and the 408 nm of the violet laser diode. A 5 mg unit size (A-30100) is also available.