For millions of years, the Aequorea victoria jelly fish held the secret to green fluorescent protein (GFP) – a protein that absorbs the energy from the blue and ultraviolet (UV) range and re-emits it as a green light. Biologists got their hands on the glowing jellyfish in the 1960s, extracting the protein and then uncovering the gene that codes for it.
By inserting this sequence into living organisms, scientists equip them with the instructions required to manufacture GFP, highlighting how genes are expressed in everything from bacteria to human cells. Specific proteins and cell types can be tagged with GFP, allowing researchers to track their movement and interaction. Tagging the HIV virus with GFP, for instance, shows how the infection spreads.
A similar effect can be achieved with quantum dots – nanoscale semi-conductor crystals which also fluoresce under UV light. The dots can be made in many different colours and bound to proteins, allowing scientists to observe complex biological interactions. Recently, surgeons wearing special goggles identified and removed cancerous cells highlighted with quantum dots. These goggles could also be used to develop diagnostic tests and therapies for other conditions.
Bioluminescence in nature – Hundreds of living organisms produce light, although most do not fluoresce, instead getting their glow from chemical reactions. Most of these are marine creatures and bacteria, although terrestrial invertebrates (eg fireflies, inset) and fungi can also glow. Bioluminescence serves a variety of functions. In many marine animals, it provides camouflage by allowing its bearer to blend in with the surrounding light when viewed from below. In other species it is used as a form of communication or, like the anglerfish, to draw in prey. Researchers aren’t certain what the Aequorea victoria jellyfish uses its eerie GFP glow for, but some believe it may be to evade predators.