Phosphorus-proton spin-spin coupling and conformation of a dinucleoside phosphate

The phosphorus-31 nuclear magnetic resonance spectrum of beta-adenosine-3'-beta-adenosine-5'-phosphoric acid in its aqueous solution (pH = 9.2) was studied. The signal consisted of eight peaks caused by the spin-spin coupling of the phosphorus nucleus with three protons, two on the 5' carbon, and one on the 3' carbon. The coupling constants were 3.4, 6.5, and 8.1 hertz; from these values the dihedral angles of the three P-O-C-H systems were estimated.