This highly cross-adsorbed Alexa Fluor 633 goat anti—mouse IgG is labeled with our bright, photostable Alexa Fluor 633 dye and is prepared from affinity-purified antibodies that react with IgG heavy chains and all classes of immunoglobulin light chains from mouse. To minimize crossreactivity, it has been adsorbed against bovine IgG, goat IgG, rabbit IgG, rat IgG, human IgG and human serum. Fluorescence of this long-wavelength Alexa Fluor dye is not visible to the human eye but is readily detected by most imaging systems.