Ammonia Ratchet (image) DOE/Pacific Northwest National Laboratory Share Print E-Mail Caption Two copies each of three proteins (in different colors) make up the nitrogenase complex. In this image, the spots where chemistry happens are highlighted as stick-and-ball molecules. Credit Simone Raugei/PNNL Usage Restrictions Please credit Raugei/PNNL Share Print E-Mail 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.