Tagging Proteins (IMAGE) Rice University Caption Rice University scientists have discovered a method to tag proteins with a controllable enzyme switch. When prompted, fragments of a tRNA synthetase come together and charge a tRNA with a bio-orthogonal amino acid (N3), which is inserted as a recognizable tag into all subsequent proteins made in the cell. Credit The Silberg Research Group/Rice University Usage Restrictions For news reporting purposes only. 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.