A nuclear magnetic resonance study of the conformations of triribonucleoside diphosphates, diribonucleoside phosphates, 5′-ribonucleoside phosphates, and ribonucleosides of uracil and cytosine; temperature dependence of the base proton chemical shifts

The temperature dependence of the nuclear magnetic resonance spectra of U, C, 5′-UMP, 5′-CMP, UpU, and CpU indicates a specific deshielding of the base proton at position-6 by an hydroxyl, phosphodiester, or phosphate group at position-5′, and demonstrates that in these compounds the bases exist in the anti conformation. Similar experiments on the wobble pair UpUpU and UpUpC suggest that the spatial arrangements of both trinucleoside diphosphates are identical, and that in these arrangements the bases are predominantly in the anti conformation.