NMR spectroscopy of the ring nitrogen protons of uracil and substituted uracils; relevance to A psi base pairing in the solution structure of transfer RNA.

The chemical shifts of the well-resolved ring nitrogen protons of uracil and a series of substituted uracils, including pseudouridine (5-ribosyl-uracil) and uridine (1-ribosyl-uracil) were determined using nuclear magnetic resonance (NMR). The observed chemical shifts suggest the existence of an atypical syn conformation for pseudouridine in the Apsi base pair in regulatory tRNAs in solution.