By Jason Palmer

Science and technology reporter, BBC News

Under UV light, the worms turned blue and were paralysed Scientists have shown off an effect not unlike that of the "phasers" in the show Star Trek - but it only works on tiny worms called nematodes. They used a special molecule that, when exposed to ultraviolet (UV) light, changes its shape. When the worms were fed this molecule and then exposed to UV light, they exhibited paralysis. But when the worms were again exposed to visible light, they regained their ability to move. The work is published in Journal of the American Chemical Society. The authors claim the research could have therapeutic applications. The phaser is a fictional invention in the Star Trek TV shows and films, a gun-like device that can stun or kill adversaries. The effect in this study is down to the molecule dithienylethene. This belongs in a family of compounds known as "photoswitches", which reversibly change their shape in response to light. While some so-called photodynamic therapies already make use of light to release chemicals or make them more reactive, only photoswitches can be returned to their starting shape, on exposure to light of a different colour. They are routinely used in chemistry experiments to investigate fundamental processes, but the researchers from Simon Fraser University in Canada say their work is the first time the photoswitching effect has been demonstrated in a living animal. Stop light The team started with tiny, transparent Caenorhabditis elegans nematode worms, an animal frequently employed in scientific research. Therapy using light could benefit from the control of photoswitches After feeding them a solution containing dithienylethene and exposing them to ultraviolet light, they turned blue - because the "switched" form of the molecule is blue. The worms remained paralysed until exposed to normal light, which returned the dithienylethene molecules to their starting condition and the worms to theirs. Neil Branda, lead author of the research, said that a likely reason for the paralysis is that the "blue" form is much better at attracting electrons, which would interrupt metabolic pathways in the worms and starve them of energy. "I'm not convinced there's a legitimate use of turning organisms on and off in terms of paralysis, but until somebody tells me otherwise, I'm not going to say that there isn't an application," Professor Branda told BBC News. The researchers are more interested in the demonstrating the potential use of photoswitches in "photodynamic therapies" within the body. Doctors use light-sensitive materials and photo-reactions in medicine to treat certain forms of cancer. "Right now, [photodynamic therapy] tends not to have as much control as the clinicians would like, so we have the potential opportunity to be able to turn the therapy off and on," Professor Branda said.



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