With a little help from a fluorescent protein, mammalian cells have been transformed into living lasers. This discovery could help improve imaging of living cells, enabling researchers to explore what's going on inside.
Laser stands for light amplification by stimulated emission of radiation, where amplification is usually achieved using dyes or crystals sat between two mirrors. Light is amplified by bouncing it between the two mirrors through a gain medium, which increases its power.
There was already some evidence that green fluorescent protein (GFP) could support lasing, but no-one had tried using the protein while it was still inside the cell. Seok Hyun Yun and his post-doc Malte Gather, both at Harvard Medical School, US, decided to try using it as a way to mark the 50th birthday of the laser.
Normally, GFP just fluoresces when light is shone on it, but Gather and Yun discovered that when they fired very short pulses (~5ns) of blue light at a single cell expressing GFP, the protein amplified the light and the cell emitted a green laser. GFP is able to act as a gain medium for the blue light because the protein has an energy level system that is equivalent to that found in normal dye lasers.