A Nine-Ubiquitin Chain (IMAGE) California Institute of Technology Caption This structural model shows a chain of nine ubiquitins, well above the threshold length of four or more required to tag a protein for degradation. Credit Caltech/Gary Kleiger Usage Restrictions With credit as given above 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.