How does fluorescence microscopy locate particular proteins inside cells?

Fluorescence microscopy locates specific proteins within cells by utilizing molecules that act as markers, which are then visualized using specialized light filters. There are two primary methods for achieving this:1

• Fluorescent Antibodies: Researchers can inject an antigen (such as a specific protein) into an animal to stimulate the production of antibodies that react exclusively with that protein. These antibodies are then isolated, purified, and chemically linked to a fluorescent dye, such as fluorescein. When applied to a tissue sample, these antibodies bind specifically to the target protein, appearing as bright, luminescent areas against a dark background under the microscope.1
• Fluorescent Protein Tagging: Scientists can also link specific proteins to naturally occurring fluorescent markers, such as green fluorescent protein (GFP). These proteins act as tiny, internal lamps within the cell. By exciting these molecules with specific wavelengths of light, researchers can track the location and behavior of the tagged proteins in real-time.23

In both approaches, appropriate filters are essential to ensure that only the light emitted by the fluorescent markers contributes to the final image.1