Immunohistochemical staining using fluorescently labeled

Immunohistochemical stains use antibodies to identify specific constituents in tissue sections. In order to detect the site of reaction, the antibody is labeled with an enzyme that can be reacted with a suitable substrate to give a colored product. The alternative is to use a fluorescent label. The advantage of an enzyme label is that the nuclei can be counter stained thereby revealing the tissue architecture, and that the stain fades slowly, if at all, allowing the slides to be stored. 

Copper-catalyzed and copper-free click chemistries have been used for metabolic labeling and fluorescent detection of DNA and RNA synthesis in vivo. Alkyne or alkene modifications on natural nucleosides are sufficiently small to allow efficient incorporation into DNA/RNA by cellular polymerases and circumvent drawbacks of immunohistochemical staining methods using 5-bromo-2 -deoxyuridine (Br-dU), such as the poor permeability of antibodies into various tissues. 

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