| Abstract: | Approximately 17 diester phosphates from the backbone structure of yeast tRNAPhe give rise to phosphorus resonances, which are resolved in its 31P NMR spectrum. To localize these diester phosphates within the tRNA structure, 31P NMR spectra of several chemically or enzymatically modified yeast tRNAPhe species were recorded. To this end selective modifications were performed in the anticodon, the DHU, and the T psi C loop. Modifications, performed in different loop regions, give rise to perturbation of different characteristic 31P resonances. The 31P spectra were correlated with the corresponding 1H NMR spectra of the ring N hydrogen-bonded protons and interpreted in view of the X-ray results obtained on yeast tRNAPhe. It is concluded that the diester phosphate groups, which experience an unusual shift, can be accounted for in the X-ray structure in terms of hydrogen-bonded phosphates groups and diester phosphates with a diester geometry, deviating from the normal double-helical conformation. |
