The green-fluorescent azide is reactive with terminal alkynes via a copper-catalyzed click reaction (CuAAC). It also reacts with strained cyclooctyne via a copper-free click chemistry reaction to form a stable triazole and does not require Cu-catalyst or elevated temperatures. MB™ 488 Azide is a bright, green fluorescent probe with excitation ideally suited for the 488 nm laser line. MB™ 488 is bright, exceedingly photostable and pH-insensitive fluorescent dye that can be used in place of Fluorescein, Alexa Fluor 488®, DyLight 488® and other dyes excitable at a wavelength of 488 nm.