Fish-like animal emits bright and dim light

A fish-like animal found in coastal waters can emit both bright and dim versions of fluorescent light and researchers have deciphered a structural component related to this ability. The lancelet or amphioxus spends most of its time in shallow waters burrowed in the sand except for their heads and offers a unique insight into natural fluorescence and their ability to emit both bright and dim light. The study carries implications for a variety of industries who want to maximise brightness of natural fluorescence – the process of transforming blue excitation light into green emission light – including adapting fluorescence for biomedical protein tracers. Researchers at Scripps Oceanography, the Air Force Research Laboratory and the Salk Institute for Biological Sciences investigated the structural differences between the green fluorescent proteins (GFPs) associated with the two levels of light output, known to be generated by different GFPs. They discovered that only a few key structural differences at the nanoscale allowed the sea creature to emit different levels of brightness. The differences relate to changes in the stiffness around the animal’s chromophore pocket – an area of proteins responsible for molecular transformation of light, and therefore light output intensity. “We discovered that some of the amphioxus GFPs are able to transform blue light into green light with 100% efficiency (current engineered GFPs – traditional rooted in the Cnidarian phylum – only reach 60 to 80% efficiency), which combines with other properties of light absorbance to make the amphioxus GFPs about five times brighter than current commercially available GFs, resulting in effect to a huge difference,” said Dimitri Deheyn. “It is also interesting that the same animal will also express similar GFPs with an efficiency of about 1,000 times less.” The exact mechanism controlling the efficiency during blue to green light transformation remains unclear. “The most unique part of this discovery perhaps lays in the fact that for some time now, we show that different GFPs seem to have different functions within the same individual and unrelated to their ability to produce light, thus probably involving a biochemical role as well,” said Deheyn. “Nevertheless, having bright GFPs or the tool to increase brightness in current ones is critical for optimising applications of fluorescence.” The work has been published in Scientific Reports. Spectral and structural comparison between bright and dim green fluorescent proteins in Amphioxus