Goat anti-mouse IgG recognizes mouse IgG heavy and light chains. This secondary antibody was purified using antigen affinity chromatography and adsorbed against human proteins to minimize species cross-reactivity. The purified antibodies are then conjugated to Fluorescein (FITC), a small fluorescent organic molecule with a molecular weight of 473 daltons with an absorbance maximum of ~492 nm and an emission maximum of ~518 nm.