Ammonia Ratchet (IMAGE) DOE/Pacific Northwest National Laboratory 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 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.