NUCLEAR MAGNETIC RESONANCE STUDY OF CONFORMATION OF NICOTINAMIDE-ADENINE DINUCLEOTIDE AND REDUCED NICOTINAMIDE-ADENINE DINUCLEOTIDE IN SOLUTION

The findings reported here are consistent with the conclusion that the pyridine nucleotides can exist in solution as an equilibrium mixture of folded and unfolded forms. For both nicotinamide-adenine dinucleotide and reduced nicotinamide- adenine dinucleotide, addition of methanol or urea to the neutral aqueous solution leads to an increase of the ratio of the unfolded to folded forms. In the case of nicotinamide- adenine dinucleotide precise chemical shift data obtained over a wide pH range agree with the data reported by Jardetzky and Wade-Jardetzky but disagree with the data reported by Sarma, Ross, and Kaplan. On the other hand for reduced nicotinamide-adenine dinucleotide we find that, in contrast to results reported by Jardetzky and Wade-Jardetzky, the C-2 and C-4 protons of the reduced pyridine ring show chemical shifts that are essentially independent of pH in the pH range 2-10. © 1969, American Chemical Society. All rights reserved.