Conformational Analysis of the Single‐Stranded Ribonucleic Acid A‐A‐C‐C: A One‐Dimensional and Two‐Dimensional Proton NMR Study at 500 MHz

Abstract

Proton NMR studies at 300 MHz and 500 MHz are reported on the ribotetranucleotide A‐A‐C‐C. The complete 1H‐NMR spectral assignment at 20°C is given. Two‐dimensional NMR was used to elucidate spin multiplets in ‘crowded’ regions. Nuclear Overhauser enhancement (NOE) experiments made an unambiguous spectral assignment possible and yielded information on interproton distances. The N/S equilibrium of the riboses and the rotamer populations around some backbone torsion angles are presented. A large preference for N‐type ribose and γ+ and βt backbone torsions is observed, in particular in the central A – C unit of A‐A‐C‐C. Information on distances between protons of different nucleotide units, obtained from NOE experiments, constitutes a probe of base‐base stacking. It is concluded that A‐A‐C‐C offers a good model for RNA single‐strand conformation. Copyright © 1983, Wiley Blackwell. All rights reserved