The Texas Red-X goat anti—rabbit IgG is labeled with our bright, photostable, red-fluorescent dye (which contains an additional seven-atom aminohexanoyl spacer ("X") between the fluorophore and the antibody). The antibody is prepared from affinity-purified antibodies that react with IgG heavy chains and all classes of immunoglobulin light chains from rabbit. To minimize crossreactivity, it has been adsorbed against human IgG, human serum, mouse IgG, mouse serum and bovine serum.