What type of light is commonly used to excite GFP for visualization?

Green Fluorescent Protein (GFP) is known for its unique ability to fluoresce upon exposure to specific wavelengths of light. The most effective and commonly used light for exciting GFP is ultraviolet light. When GFP absorbs UV light, the energy causes the electrons in the chromophore—a part of the GFP structure responsible for its fluorescence—to reach an excited state. As these electrons return to their ground state, they emit energy in the form of visible light, typically green in color.

This excitation mechanism is critical in various applications, including microscopy, where UV light sources, such as mercury vapor lamps or LED lights tuned to UV wavelengths, are employed to visualize GFP-tagged proteins in live or fixed specimens. The specific excitation wavelength for GFP is usually around 395 nm, which falls within the ultraviolet range, making it essential for effective visualization in experiments.

Using visible light or infrared light would not provide the necessary energy to excite GFP effectively, as these forms of light do not have the appropriate wavelength to stimulate the electron transition within the protein. Laser light can also be used for GFP visualization, particularly in advanced techniques like fluorescence microscopy, but it is not universally the common choice across all setups. Hence, ultraviolet light is the best option when considering the standard practices for