Alexa Fluor 350 carboxylic acid, succinimidyl ester is an intense, blue-fluorescent dye that yields bright fluorescent protein conjugates. Alexa Fluor 350 protein conjugates are optimally excited at ~346 nm and produce bright, blue fluorescence emission at a wavelength slightly shorter than that of AMCA or AMCA conjugates, reducing Alexa Fluor 350 dye's spectral overlap with the emission of fluorescein or Alexa Fluor 488 dye.