Antibody conjugates allow for the study of specific antigens in biological systems. Such targets may include proteins (like polymerase), small molecules (like cAMP) or nucleic acids (like dsDNA). Conjugates can be made with both primary and secondary antibodies. Primary, or direct, immunofluorescence utilizes a single antibody which both detects the antigen and emits the signal. Secondary, or indirect, immunofluorescence uses two antibodies, one which recognizes the target antigen and a secondary antibody which binds to the primary antibody and emits the signal.
Antibodies can be conjugated with reporter enzymes like horseradish peroxidase (HRP) for use in assays such as Western Blot, ELISA and immunohistochemistry. Depending on the substrate it is paired with, such conjugates can yield signals that are colorimetric or fluorometric in nature. Additionally, different substrates will produce signals with different spectral properties. Some common substrates are
TMB and
Amplite Red, which yield signals at 650 nm and 585 nm, respectively.
Antibodies can also be conjugated with a variety of fluorochromes for use in applications such as flow cytometry or fluorescence microscopy. These are labels which will emit a detectable array of photons when excited. Possible fluorochromes span the spectrum from UV to Near Infrared. Common fluorochromes include markers such as FITC and Texas Red®.