The Conformation of Pyridine Nucleotides Studied by ³¹P and ¹H Fast Fourier Transform Nuclear Magnetic Resonance Spectroscopy. II. The Backbone Conformation of Dinucleotides

Using parameters derived from the component mononucleotides, β-NMN, 5′-AMP, and 5′-ADP, the 31 P n.m.r. spectra of oxidized pyridine coenzymes, recorded in the presence of coupling from the ribose protons, are analyzed with the use of extensive computer simulations. It is shown that the spectra are compatible only with gauche–gauche conformation about the C 5′ —O 5′ bonds on both the adenine and nicotinamide ends of oxidized pyridine coenzymes. The 1 H and 1 H–{ 31 P} Fourier transformed 16K n.m.r. spectra of 5′-AMP and 5′-ADP are reported and their full analysis given, and it is shown that the nucleotides exist predominantly in the gauche–gauche conformation about the C 4′ —C 5′ and C 5′ —O 5′ bonds.