The 13C and 1H nuclear magnetic resonance spectra and methods of their assignment for nucleotides related to dihydronicotinamide adenine dinucleotide phosphate (NADPH)
Abstract
The 13C n.m.r. spectra at 25·2 MHz of ribose-5-phosphate, AMP, NMN+, NAD+, NADH, NADP+, and NADPH have been assigned by use of a combination of techniques. In addition to established methods, such as comparisons of chemical shifts and coupling constants with those in model compounds, ionisation studies, and {1H}–13C heteronuclear selective decoupling experiments, we have described some novel methods of 13C spectral assignments, namely (i) addition of Eu3+ ions to induce pseudo-contact shifts in the proton spectrum to facilitate {1H}–13C decoupling experiments; (ii) the use of a graphical method of presenting results of off-resonance selective 1H irradiation experiments; (iii) paramagnetic shift predictions for 13C nuclei in non-rigid molecules in the presence of Eu3+ ions. Difficult proton assignments can sometimes be made on the basis of connecting assigned 13C signals with their corresponding proton resonance signals by heteronuclear decoupling.