Structure of the Photoreceptor 2c-cyclop (IMAGE) University of Würzburg Caption Two molecules of the new light sensor 2c-cyclop, which in darkness produces the messenger cGMP. Green light inhibits the signal chain. Credit (Image: Shiqiang Gao / Armin Hallmann, Georg Nagel) Usage Restrictions This image may only be used in connection with reports concerning the discovery of the new photoreceptor 2c-cyclase. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.