HYDROGEN-EXCHANGE MEASUREMENTS ON ESCHERICHIA COLI TRANSFER RIBONUCLEIC ACID BEFORE AFTER AND DURING ITS AMINOACYLATION

The conformation of transfer ribonucleic acid has been compared with aminoacyl transfer ribonucleicacid by using the Sephadex hydrogen-tritiumexchange technique. The exchange-out kinetics of the acylated and unacylated transfer ribonucleic acid are almost identical, suggesting that secondary structures are closely similar. However, a small but consistent difference was observed. The aminoacyl transfer ribonucleic acid seems to possess three or four more stabilized hydrogens than the unacylated transfer ribonucleic acid, representing approximately 4% the measurable structure. Thus, the aminoacyl transfer ribonucleic acid has at least as much structure involving hydrogen bondsas has unacylated transfer ribonucleic acid and perhaps slightly more. In addition, a new application of hydrogen exchange is described. It was possible to carry out measurements that should detect changes in transfer ribonucleic acid structure that might occur during the transient interval in which it binds to the amino acid-adenosine monophosphate- synthetase complex, undergoes acylation, and then dissociates. © 1969, American Chemical Society. All rights reserved.