With an absorption maxima at 702 nm, the isomer-free, amine-reactive Alexa Fluor 700 carboxylic acid, succinimidyl ester and its conjugates can be excited with a xenon-arc lamp, far-red diode lasers or dye pumped lasers operating in the 675—700 nm range. The Alexa Fluor 700 dye provides bright fluorescence emission with a peak at 723 nm. Fluorescence of this long-wavelength Alexa Fluor dye is not visible to the human eye but is readily detected by most imaging systems. A 1 mg unit size (A-20010) is also available.