Proton Transfer in Ionized Dimethyluracil (IMAGE) DOE/Lawrence Berkeley National Laboratory Caption Uracil is one of the four bases of RNA (carbon atoms are brown, nitrogen purple, oxygen red, hydrogen white). Because methyl groups discourage hydrogen bonding, methylated uracil should be incapable of proton transfer. But after ionization of methylated uracil dimers, a proton moves by a different route, from one monomer to the other. Credit Lawrence Berkeley National Laboratory, University of Southern California Usage Restrictions with credit as given 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.