The Alexa Fluor 488 donkey anti—sheep IgG is labeled with our bright, photostable, green-fluorescent Alexa Fluor 488 dye and is prepared from affinity-purified antibodies that react with IgG heavy chains and all classes of immunoglobulin light chains from sheep. To minimize crossreactivity, it has been adsorbed against mouse, rabbit, bovine and human sera and human IgG.